GENETIC TESTING FOR BREAST CANCER PREDISPOSITION

BREAST CANCER MANAGEMENT 0039-6109/99 $8.00 + .OO

GENETIC TESTING FOR BREAST CANCER PREDISPOSITION

Marion Gauthier-Villars, MD, Sophie Gad, BSc, Virginie Caux, BSc, Sabine Pages, BSc, C6cile Blandy, PhD,

and Dominique Stoppa-Lyonnet, MD, PhD

In the late 1980s, the knowledge of genetic predisposition to breast cancer was limited to the rare descriptions of large families in which at least one woman in two was affected with breast cancer in each generation. It was thought that a woman whose mother or sister had been affected was at greater risk than the general population. At that time, the ability to understand the origins of these family histories seemed quite remote. Between December, 1990, and De- cember, 1995, however, genetic epidemiologic research and positional cloning techniques improved the understanding and the ability to assess the risk of women with a family history of breast cancer. It is now increasingly possible to tell a woman whether her risk is that of the general population or whether it is many times higher.

It must be remembered that the main purpose for breast cancer predisposition testing is to provide women at high risk with better supportive care. Today, a major challenge for clinical research is to identify the modalities for prevention that will allow reduction of the morbidity and the mortality linked to a high predisposition to breast cancer.

GENETIC PREDISPOSITION TO BREAST CANCER: EPIDEMIOLOGIC ASPECTS

Epidemiologic studies have shown that a woman whose first-degree relative has experienced breast cancer may herself have a breast cancer risk that is 1.7

This work was supported by EC Biomed 2: Demonstration Project Familial Breast Cancer: Audit of New Development S in Medical Practice in European Centres; and by la Fondation de France 9703929. Sophie Gad is supported by a grant from the MENRT (MinistGre de 1’Education Nationale, de la Recherche et de la Technologie).

From the Service de Genetique Oncologique, Institut Curie, Paris, France

SURGICAL CLINICS OF NORTH AMERICA

VOLUME 79 * NUMBER 5 * OCTOBER 1999 1171

1172 GAUTHIER-VILLARS et a1

to 4.0 times greater than that of the general p0pulation.4~ Thus, a positive family history is itself a risk factor for breast disease. That finding, however, reveals nothing about whether the risk is environmental, cultural, or genetic in origin, about the range of variation in risk from family to family, nor about the relative risk for a woman within a given family.

To provide better understanding of the genetic factors, genetic epidemiologic studies, also termed segregation studies, were carried out in the late 1980s based on the analysis of breast cancer distribution among the relatives of affected women who had not been selected for their family history. These studies established that a genetic predisposition to breast cancer accounts for a proportion of familial breast cancer cases; the others arise as a chance cluster because of the incidence of the disease among the general population.'*

Features of the genetic predisposition include dominant autosomal inheri- tance, high penetrance (in which case the risk of breast cancer for a woman carrying the genetic trait is in the range of 67% by age 70 and 80% by age 80) (Table 1 and Fig. l), 0.003 gene frequency, and 0.006 gene carrier frequency.'z,'5 Thus, 1 woman in 20 with breast cancer is a carrier of such a predisposition, which corresponds to a rate of 1 woman in 200 among the general population. This frequency makes genetic predisposition to breast cancer one of the most widespread hereditary pathologies.

This very significant risk of breast cancer is obvious in family histories when the trait is inherited through mothers and runs through two or three generations. The family history is less obvious, however, when the trait is inherited through fathers who have few sisters or whose sisters did not inherit the predisposition.

These segregation studies, therefore, indirectly pointed towards the existence of one or more genes that carry a predisposition to breast cancer. Indeed, although they single out the alteration of only one major gene in a given family, they do not rule out the existence of a genetic heterogeneity, that is, the implication of different genes in different families. Segregation studies have been essential in localizing predisposing genes to chromosomes and are important in analyzing a family history. These studies make it possible to evaluate whether the history of a particular family is caused by an underlying genetic predisposi-

Table 1. RISK OF BREAST CANCER DESCRIBED IN DIFFERENT STUDIES: FAMILY STUDIES AND POPULATION STUDIES

Risk of Breast Cancer for Women with Unspecified "Genetic Predisposition: Results of Family Studies

in Early 1990s

Segregation

(Reference 12, 15) Analysis

Risk of Breast Cancer for Women Carrying Specific Genetic Mutations: Results from Later Family Studies

BRCAl: 185delAG BRCA2:

BRACl BRCA2 6174delT (Reference (Reference (Reference BRCA2: 999del5

22) 23) 58) (Reference 61)

Risk by 38% 73% (49-87) 28% (9-44) 33% (23-44) 17% (9.1-25.9)

Risk by 67% 87% (72-95) 84% (43-95) 56% (40-73) 37.2% (22.4-53.9) age 50

age 70

GENETIC TESTING FOR BREAST CANCER PREDISPOSITION 1173

80 - 70 -- 60 --

c) 50--

40- ' 30--

20 --

- 0 - - - T 1 I I

30 40 50 60 70 80

A 25 T

Years

20

* 1s B & 10 u I.

5

0 20-29 30-39 4049 50-59 60-69 70-79 >80

B Years

Figure 1. Breast cancer risk of predisposed (hatched bars) and nonpredisposed (solid bars) women. A, Lifelong. B, By 10-y intervals. (Data from Claus EB, Risch NJ, Thompson WD: Genetic analysis of breast cancer in the cancer and steroid hormone study. Am J Hum Genet 48:232, 1991; and Easton DF, Bishop DT, Ford D, et al: Genetic linkage analysis in familial breast and ovarian cancer: Results from 214 families. Am J Hum Genet 52:678, 1993.)


tion or by chance. Figure 2 shows the probabilities for genetic predisposition for two sisters affected with breast cancer, according to age at diagnosis.'*, l5

THE TWO MAJOR PREDISPOSING GENES IDENTIFIED: THE BRCA7 AND BRCAP GENES

Four breast cancer predisposing genes were identified between December, 1990, and May, 1997 p53, BRCAZ (BReastCAncer), BRCA2, and PTEN (Phos- phataseTENsin). Among these, p53 and PTEN are responsible for specific individual and family presentations, respectively the Li-Fraumeni syndrome and Cowden disease (see Addendum 1). Another predisposing gene, BRCAS, has been localized to chromosome 8%. 53 but is yet to be identified. All the mysteries concerning the genetics of predisposition to breast cancer are not yet disclosed. It is likely that other genes are in~olved,'~ but their alterations could be associated with a lower risk of breast tumor, with the risks associated with BRCAZ and BRCA2 remaining the major ones. One of the candidate genes is the ataxia- telangiectasia gene (see addendum 2).

Localization and Identification of the BRCA7 and BRCAP Genes

The chromosomal localization of the BRCAl and BRCA2 genes was achieved by genetic linkage studies that searched in families with multiple occurrences of breast cancer for cotransmission of the disease and common genetic markers with a known location on the genome. The BRCAZ gene was localized on chromosome 17 and BRCA2 on chromosome 13.15, 67 Shortly after the BRCAZ locus was ascertained, analyses of families with multiple occurrences of breast and ovarian cancer determined that the same locus was involved, showing that families with this genetic predisposition to breast cancer are also at risk for ovarian cancer.'5, 43

" '

25 35 45 55 65

Years

Figure 2. Genetic predisposition probabilities of a woman (A) and two sisters (B) with breast cancer according to age at diagnosis.


Physical mapping, of the regions pinpointed by the linkage studies led to the identification of numerous genes. The clue that led to belief that one of these genes corresponded to the gene searched for was the presence of a constitutional alteration, a germ-line mutation, in affected individuals from kindred linked to the BRCAl or BRCA2 loci. After 4 years of research focused on the long arm of chromosome 17, the BRCAl gene was identified in October, 1994.42 The BRCA2 gene was identified in December, 1995, 1 year after its

According to linkage analyses performed in a large set of 237 families, each with at least four breast cancer cases, BRCAZ and BRCA2 alterations account for 28% and 37%, respectively, of cases of hereditary breast cancer occurring in a breast cancer-only context and for 80% and 15%, respectively, of cases occurring in a breast and ovarian cancer context.23 Thus, although BRCAl or BRCA2 alterations explain most of the familial forms of breast and ovarian cancers, only 65% of hereditary breast cancer-only cases are linked to one of these two genes.

h6

Putative Physiologic Role of the BRCA1 and BRCA2 Proteins

The primary sequence of BRCAl and BRCA2 proteins, deduced from the nucleotide sequence of the coding region of the BRCAl and BRCA2 genes, did not yield much information on the function of the BRCAl and BRCA2 proteins, and no homologous proteins have been reported to date. It is interesting to note, however, that the BRCAl protein has a RING finger domain suggesting either protein-protein or protein-DNA interactions. Moreover, BRCAl and BRCA2 have BRCT (BReast cancer CTer) domains also found in proteins interacting with the p53 protein and in proteins involved in the DNA repair process.II Cellular colocalization experiments carried out with various proteins, including Rad51, a key protein involved in the repair process of double-strand breaks, and knock- out of these genes in mice, indicate that the BRCAl and BRCA2 proteins are probably involved in DNA repair.68

Alterations of the BRCAl or BRCA2 gene described in predisposed individuals generally lead to a nonfunctional pr~ te in . '~ These constitutional alterations, associated with the inactivation of the second allele during tumorigenesis, result in a total loss of function of the BRCAl or BRCA2 protein in tumors.ss Thus, the probable role of the BRCAl and BRCA2 proteins in the repair of DNA alterations, whether spontaneous or radio-induced or chemo-induced, raises questions concerning the radiosensitivity of tumors and about the mutagenic effect on normal tissues of tools used for the follow-up and management of patients. No study has yet examined the delayed manifestations of radiosensitivity in normal tissues of predisposed subjects. Epidemiologic studies investigating the contralateral cancer risk in women irradiated for a first cancer and comparing it with that of nonirradiated women will probably be lengthy, because they require a large number of patients. In vitro studies directly quantifying the repair rate associated with a mutation and, more specifically, the rate of inappropriate repairs introducing additional mutations should provide information more quickly. Thus, although the mutant phenotype of BRCAl or BRCA2 mutation carriers has not yet been demonstrated, it can nevertheless be strongly suspected.

Laboratory Identification of BRCA7 and BRCA2 Germline Mutations

Numerous studies of the BRCAZ and BRCA2 genes performed during the past 4 years allow the description of a large number of mutations. In February,

1176 GAUTHIER-VILLAS et a1

1999, the Breast Cancer Information Core (BlC)? a database for BRCAZ and BRCA2 mutations enriched by the contributions of laboratories working in this field, contained 1070 different variants, of which 664 are associated with a deleterious effect. More than 90% of these mutations lead to a nonfunctional truncated protein. In most reported cases, these truncating mutations are point or small sized mutations spread over the entire coding sequence that numbers 5592 nucleotides for BRCAl and 10,443 for BRCA2. Moreover, large rearrangements may occur in 10% to 25% of BRCAZ truncating 48-50

The detection of these rearrangements requires different screening methods, thereby considerably increasing the necessary laboratory work.

Other mutations are missense mutations substituting one amino acid for another. Except for a few cases, their effect on the corresponding BRCAl and BRCA2 proteins is poorly understood. It is likely that functional tests will soon provide more information on these truly deleterious missense mutations. Until then, genetic counseling must be undertaken with great caution.

Among certain populations ( eg , Icelandic, Ashkenazi Jewish) only a few mutations are responsible for genetic predisposition to breast and ovarian cancer. The incidence of these mutations is linked to founder’s effects1f61 (see Addendum 3), thereby reducing the experimental work necessary to identify the mutations in families at risk. Outside these populations, the initial search for a mutation in an untested family is a time-consuming and arduous task requiring the combina- tion of several technical approaches. At present, the maximum sensitivity of the screening techniques, which combine both sequencing used to detect point and small sized mutations and Southern blotting or other methods to detect large gene reatrangements, is assessed at about

The probability of detecting a BRCAZ or BRCA2 germline mutation in an individual referred for genetic consultation in the context of familial breast or ovarian cancer relies on three parameters: the probability of the person’s being a carrier of a predisposing gene, the contribution of the genes studied to this predisposition, and the sensitivity of the detection techniques used. The probability of identifying a BRCAZ or BRCA2 mutation after direct sequencing, according to the proband and her family history, is shown in Table ZZ5 These values might be underestimated, however, because most missense mutations have not been taken into account, and screening for large rearrangements has not been performed.

If the family mutation has not been identified, testing healthy relatives for predisposition has a limited usefulness. A negative test result for a healthy woman at increased risk for breast cancer because of a very strong family history will not tell with certainty whether she did not inherit the family mutation or whether she carries an unidentified mutation in BRCAZ or BRCA2 or even a mutation in an unidentified gene. For a negative test result to be truly meaning- ful, showing true absence of predisposition, the genetic mutation responsible for the cancer in a given family must be identified. Priority is given to testing first the family member most likely to be a carrier, that is, the woman who is already affected.

RISKS ASSOCIATED WITH ALTERED BRCAl AND BRCA2 GENES AND SPECIFIC FEATURES OF BRCA1/2 TUMORS

Assessment of the Risks of Breast Cancer Associated with an Alteration of the BRCAl orBRCA2 Gene

Although segregation analyses gave indications concerning genetically based risks of breast cancer, it was necessary to reassess the risks of breast (and

Tabl

e 2.

MO

DE

LED

PR

OB

AB

ILIT

IES

TH

AT A

WO

MA

N W

ITH

BR

EA

ST

CA

NC

ER

UN

DE

R 5

0 Y

EA

RS

OF

AGE

CA

RR

IES

A B

RC

AI

OR

BR

CA

P M

UTA

TIO

N

Any

Rel

ativ

e w

ith B

reas

t P

roba

nd w

ith B

ilate

ral

Pro

band

with

M

odel

ed P

roba

bilit

y M

odel

ed P

roba

bilit

y M

odel

ed P

roba

bilit

y of

Tu

mor

A

ny R

elat

ive

Bre

ast T

umor

or

Bre

ast T

umor

of

Mut

atio

n in

of

Mut

atio

n in

M

utat

ion

in B

RC

Al

< 5

0 y

with

Ova

rian

Tum

or

Ova

rian

Tum

or

< 4

0 y

BR

CA

l (Y

o)

BR

CA

P (Y

o)

or B

RC

AP

(%)

Yes

No

No

No

10.1

14

.5

25

Yes

No

No

Yes

28.2

11

.6

40

Yes

No

Yes

No

41.5

9.

5 51

Yes

No

Yes

Yes

71.1

4.

5 76

N

o Yes

No

No

22.9

12

.5

35

No

Yes

No

Yes

22.9

12

.5

35

No

Yes

Yes

No

65.0

5.

7 71

N

o Yes

Yes

Yes

65.0

5.

7 71

Yes

Yes

No

No

22.9

12

.5

35

Yes

Yes

No

Yes

50.9

7.

9 59

Yes

Yes

Yes

No

65.0

5.

7 71

Yes

Yes

Yes

Yes

86.7

2.

2 89

Dat

a fr

om F

rank

TS,

et a

l: Se

quen

ce a

naly

sis

of B

RC

Al

and

BR

CA

2: C

orre

latio

n of

mut

atio

ns w

ith f

amily

his

tory

and

ova

rian

can

cer

risk.

J C

lin O

ncol

162

417,

199

8.


ovarian) cancer associated with a BRCAZ or BRCAZ alteration. The first assessment studies were carried out in the families who had contributed to the identification of the BRCAl and BRCA2 genes. They showed an 87% (confidence interval [CI] = 72-95) risk of a first breast tumor associated with BRCAZ by age 70, and an 84% risk (CI = 43-95) associated with BRCA222,23 (see Table 1). The risk of contralateral breast cancer was assessed as 64% by age 70 for BRCAZ, and 52.3% (CI = 41.1-61.4) for BRCAZ.aa Thus, women in these families have a risk for a contralateral tumor that is three times as high as the risk of women affected with breast cancer, taken as a whole. This high incidence of contralateral tumors is supported by independent studies5, @ Current knowledge does not allow assessing the risk of a second ipsilateral tumor (as differentiated from a local recurrence).

Following the family studies, it was important to reassess these risks in population studies, that is, with no selection for family history. It has been possible to study a large number of people from a given population when a relative mutation homogeneity linked to a founder's effect has been identified. Two specific populations have been studied, the Ashkenazi Jewish population of Washington D.C. and the population of Iceland.58, 6z The systematic study of these mutations in a set of healthy subjects (first study), or in breast cancer patients recorded within a given time period (second study), and the reconstruc- tion of each subject's family history allowed the reassessment of the breast cancer risk of women carrying the trait. In the Ashkenazi population, in which one of the three mutations in BRCAZ (185delAG;5382insC) and BRCAZ(6174delT) is present in roughly 2% of subjects, the risk of breast cancer in these subjects is 56% by age 70 (CI = 40-73)58 (Table 1). This study shows no disparity in risk among the three mutations studied. In the Icelandic population, the 999de15 mutaion in the BRCAZ gene is associated with a 37.2% (CI = 22.4-53.9) risk of breast cancer by age 7062 (Table 1).

How can these apparent differences between the results of the family studiesz2, 23 and those of the population 62 be explained? First, in the studies of BRCAP, 58 and BRCA2,23* 62 the confidence intervals among the four studies are relatively wide and overlap each other. The nature of the populations studied and the possibility of comparing them must also be considered. The Icelandic study was performed retrospectively. It was based on data collected from records of breast cancer cases diagnosed in 1910. It is known, however, that in the last five decades the risk of breast cancer for women who have a mutation in BRCAZ has increased threefold." Therefore, it is possible that the way in which index cases were recorded produced an apparently lower average risk that is not representative of the present general population. Finally, it is highly likely that these differences are caused by modifying factors, either environmental or genetic, in the familial forms of breast cancer. None of these factors have been identified to date, and detecting them is a crucial challenge. Thus, it can be reasonably assumed that the risk of breast cancer for a woman who carries a BRCAZ or BRCA2 mutation and who also belongs to a family with a history of multiple occurrences of breast cancer is close to that shown in the first studies, that is, in the range of 80% by age 70.17

Risks of Ovarian Cancer Associated with BRCAl or BRCAP Alterations

The risks of ovarian cancer described in family and population studiesz2, z3, 58 are presented in Table 3. Even though the confidence interval is wide, it


Table 3. RISK OF OVARIAN CANCER FOR WOMEN CARRYING SPECIFIC GENE MUTATIONS

BRCA 1/185delAG BRCA 1/5382insC

BRCA 1 BRCAP BRCA2/6174delT Mutation (Reference 22) (Reference 23) (Reference 58)

Risk by age 29% 0.4% (0-1%) 7% (2%-14%)

Risk by age 44% 27% (047%) 16% (6%-28%) 50 (1 6%40%)

70 (28%-56%)

should be noted that the risk linked to a BRCA2 alteration is lower. The 44% risk of ovarian cancer associated with BRCAZ alterations represents an average estimated risk for the tested families taken as a whole. An interfamily heterogeneity of the ovarian cancer risk has been observed. In some families this risk is significant, closer to 80%; in others, who represent most families, it is closer to 20%.16 Correlation studies did not, however, provide clear evidence for an association between the location of the mutation and the risk of ovarian cancer.z6, 57 Environmental factors, or even other genetic factors, could account for this disparity in risk.

Pathologic Features and Prognosis of Breast Cancer Associated with BRCAl or BRCAZ

The vast majority of breast cancer cases associated with a BRCAl alteration are adenocarcinomas of the invasive ductal type; however, an excess of medullary forms have been reported (13%).*, 19, 35 As a rule, BRCAl-associated cancers exhibit a poor histologic grade associated with a significantly high mitotic index." 30, 35 Most of these tumors are hormone re~eptor-negative.~~, 51,

Most cancers associated with a BRCA2 alteration are also of the ductal invasive type, but they do not show a high incidence of medullary tumors.8, 35 Their histologic grade is also poor as well, because of a low rate of tubule formation rather than a high mitotic index.35 The hormone dependency of BRCA2-associated cancers has not been definitively established; the few studies available indicate that the distribution of the hormonal receptors is the same as that of sporadic breast cancers.*, 33

Studies on survival in patients with familial breast cancer reported that their prognosis is more favorable than that of patients with nonfamilial breast cancer.65 Studies more specifically examining the prognosis of patients affected with BRCA1- or BRCA2-associated breast cancer, however, report very conflicting findings. Some have reported a more favorable pr0gnosis,4~ others report a poorer one? 24 and others report no difference.36, 64 Several factors may account for these different findings, including the lack of power of some studies, late ascertainment of diagnosis for some genetic studies, lack of adjustment according to clinical staging in some studies, and nonequivalent groups, among others. More extensive studies are required for definitive assessment of the prognosis of BRCAZ- or BRCA2-associated breast tumors.


GENETIC COUNSELING

The aim of genetic counseling is to provide an answer to a woman wonder- ing about her own risk of breast cancer, and possibly about that of her relatives, and to inform her about relevant possibilities of prevention and screening. The tools that allow assessing the risk of breast cancer are genetic epidemiology and, for an increasing number of women, molecular genetics. The complexity of molecular analysis, because of different meanings of a negative result, leads to two situations. In the first, a woman who already has breast cancer wishes to understand the origin of her disease, not only for her own sake but also for that of her relatives. In this situation, the goal is to identify the genetic alteration responsible for the family history. In the second situation, an unaffected person asks for a consultation because an alteration has been identified in one of her relatives. The approach is that of predisposition testing.

Recommendations regarding genetic testing for late-onset disorders, predisposition for cancer, and, more specifically, predisposition for breast and ovarian cancer have been published in the United States and in other countries by numerous scientific or medical societies and task forces. Among them are the American Society of Clinical Oncology (ASCO)? the American Society of Human Genetics (ASHG)," the National Society of Genetic Counselors (NSGC),4l the task force of the Cancer Genetics Studies Consortium (CGSC) of National Human Genome Research Institute,'", 27 the task force of the National Institutes of Health-Department of and the French National Institute of Health and Medical Research.lS All strongly recommend that informed consent be obtained from candidates for genetic testing through pretest counseling sessions during which the basic points for informed consent, listed in Table 4, are discussed.

Results must be disclosed during a post-test counseling session. It is strongly encouraged that the psychosocial effect of genetic testing be assessed, whatever the result of the test. Testing is restricted to persons with at least a 20% probability of being a carrier of a BRCAl or BRCAZ muta t i~n .~ , '~ Therefore, testing the general population is not recommended until additional means of evaluating breast cancer risk are available?,

There is not a consensus, however, on how the information should be conveyed to relatives once a mutation has been detected in a family or on who should provide genetic counseling. In the ASHG statement, information may be conveyed to relatives without the permission of the person tested, provided that

Testing children is not recommended.

Table 4. BASIC ELEMENTS OF INFORMED CONSENT FOR GERMLINE DNA TESTING

1. The information on the specific test being performed 2. The implications of positive and negative test results 3. The possibility that the test will not be informative 4. The options for risk evaluation without genetic testing 5. The risk of passing a mutation to children 6. The technical accuracy of the test 7. The fees involved in testing and counseling 8. The risk of psychosocial distress 9. The risk of disorientation by an insurance company or an employer

'

10. The confidentiality issues 11. The options and limitations of medical surveillance and screening following testing

From American Society of Clinical Oncology: Statement of the American Society of Clinical Oncol- ogy: Genetic testing for cancer susceptibility JAMA 141730, 1996; with permission.


some benefit may be expected from early monitoring; in the ASCO statement, the patient’s permission must be obtained; in the French recommendations, information may be given to others only by the person tested. In the ASCO statement, genetic counseling may be provided by clinical oncologists, but in the NSGC, CSGH, and ASHG statements, and others, it can only be given by geneticists or genetic counselors. All recommend a multidisciplinary approach involving geneticists, genetic counselors, psychologists, gynecologists, radiolo- gists, surgeons, and medical oncologists.

SUPPORTIVE CARE FOR PREDISPOSED WOMEN

The appropriate supportive care for women carrying a BRCAZ or BRCA2 alteration is a complex issue, because essential information is either incomplete or simply lacking, such as the prognosis for breast cancers associated with BRCAZ or BRCA2 alterations, the effect of ionizing radiation (mammography and radiotherapy), the efficacy of mammography in young women, and the efficacy of chemoprevention. Nevertheless, it is necessary to develop supportive care modalities based on the knowledge that is available. There is a consensus among the various reports concerning recommendations for a surveillance protocol that involves a bi-annual examination by a specialist and an annual mammo- gram, beginning between the ages of 25 and 35.10,18,b3

The main issue of debate is prophylactic mastectomy, which is generally proposed as an option to women with a BRCAl or BRCA2 mutation. It is a very difficult decision for women to make. The factors involved can be classified in terms of a negative effect to positive effect ratio. The negative effects of prophylactic mastectomy include psychological distress, altered quality of life, contin- ued risk of breast cancer, and morbidity linked to surgical complications. The positive effects include reduced risk of morbidity and mortality caused by breast cancer, an end to the anxiety caused by the fear of breast cancer, and reduced morbidity resulting from surveillance and radio- or chemotherapy. It is difficult to determine such a ratio, not only because a large number of parameters are involved and their significance is not always clearly established but also because the coefficient of some parameters varies from one woman to another.

Whatever management protocol is chosen, it is essential to keep a record of its follow-up. Ideally, every woman at risk should be involved in a clinical research Today, much hope lies in the development of chemoprevention. Although recent results in this field are encouraging, they are not sufficient to tell whether women carrying a BRCAZ or BRCA2 mutation derive any benefit from chemoprevention.21

CONCLUSION

The recent progress in understanding genetic predisposition to breast cancer has shed some light on questions that have long existed. (Fig. 3) A woman whose mother or sister carries BRCAl or BRCA2 mutation has an average risk of a predisposition to breast cancer of 50%. Genetic testing can drop this risk or raise it to either extreme of the probability scale: to 0% or to 100%. Such a finding is a considerable achievement, but we must keep pushing ahead. One of today’s major challenges is to understand the factors that modify a risk of breast cancer in order to identify the 20% of women who, although predisposed, do not develop cancer. Identifying these modifying factors and acquiring a


Figure 3. Copy of a letter dated 1951 found in the medical archives of The lnstitut Curie. The man who wrote the letter wondered about the origin of his family history, screening, and prevention. The letter states, “Doctor, Faced with successive deaths caused by the same terrible disease, I wonder if this curse is not hereditary or at least if the ma- ternal branch of my family did not present predispositions. As my daughter born Feb- ruary 5, 1949, is the exact replica of my mother, I am beginning to fear for her. How can this frightful disease be detected and prevented? I don’t believe there are cancer specialists in Morocco. . . . I ’ (Courtesy of The lnstitut Curie, Paris, France.)

deeper knowledge of the BRCAl and BRCA2 protein functions may make new methods of prevention possible. Another challenge is to win social acceptance of genetic testing for adult-onset diseases to prevent discrimination caused by a deleterious genetic test. This is an issue that health insurance companies and employers, as well as the scientific and medical community, must address.

ADDENDUM 1: P53 AND PTEN, TWO GENES WHOSE ALTERATIONS ARE RESPONSIBLE FOR SPECIFIC FORMS OF FAMILIAL BREAST CANCER

According to its historical definition, the Li-Fraumeni syndrome is the familial association of a sarcoma in the index case, occurring by age 45, with two other cancer cases occurring by age 45 (most often brain tumor, breast cancer, or hemopathy), or with sarcoma, regardless of the age, affecting two relatives, at least one of whom is a first-degree relative of the index case and the other a first- or second-degree relative.37 These tumors, often multiple, are of early onset, occurring frequently in childhood. Germline mutations of p53, whose protein is involved in the control of the cellular cycle, have been identified


in approximately 50% of families that conform to the classic definition of the syndrome.40 This significant cancer risk is inherited according to the dominant mode. The incidence of constitutional p53 mutations in women who develop breast cancer before age 40 has been assessed at about l%.7,54 Management for a p53-mutation carrier is extremely complex, and individuals at risk must seriously consider being tested.

Cowden disease, or multiple hamartoma syndrome, is a rare pathology, particularly in its complete form.39 It is responsible for a very small proportion of breast cancers, fewer than 1 in 1000. This disease is characterized by the presence of hamartomatous lesions of the skin and the oral cavity and is associated most often with nonmalignant tumors of the thyroid or the digestive tract. It is a hereditary pathology, inherited according to the dominant autosomal mode. More than 50% of women who carry this trait present a fibrocystic disease of the breast, with or without cellular atypias, that in one half the cases are associated with adenocarcinoma (28% of women carriers). The gene responsible, PTEN, has been identified

ADDENDUM 2: ATAXIA-TELANGIECTASIA IN THE HETEROZYGOUS STATE: A GENE POSSIBLY ASSOCIATED WITH BREAST TUMOR RISK

Ataxia-telangiectasia is a hereditary disease, inherited according to the reces- sive mode, associating cerebellar degeneration, immunodeficiency, hypersensi- tivity to ionizing radiation, and predisposition to early-onset tumors occurring in childhood. The gene responsible for the disease, ATM, has been identified recently.5z Its corresponding protein is involved in the control of the cellular cycle during the DNA repair process. Parents of affected children, necessarily heterozygous at the locus of the disease, present above normal in vitro sensitivity and would be at greater risk of breast cancer than the general population. Indeed, comparing cancer incidence among these parents and their relatives with that in the general population, a few studies have reported that AT heterozygous (HetAT) women have a breast cancer risk about three times as high.h, 59

Considering the frequency of HetAT among the general population (in the range of 0.5%), alterations of the ATM gene could account for 2% (CI = 0.5 to 6.5) of breast cancer cases. Because of the radiosensitivity of heterozygotes, if this work is confirmed, identification of the HetAT trait could bring about changes in the management of female carriers. The systematic search for mutations in the ATM gene in a large number of women who have breast cancer will make it possible to determine the actual role of HetAT in predisposition to breast cancer.

ADDENDUM 3: NEOMUTATION, FREQUENT MUTATION, AND FOUNDER’S EFFECT

Constitutional mutations are generally inherited from a carrier parent. In a small percentage of cases, the number varying according to the genetic trait observed, some parents do not carry the mutation. It has occurred in one of their gametes. This is a neomutation. Surprisingly, if one considers the diversity of BRCAZ and BRCA2 mutations, their neomutation rate seems low.

In certain populations, a single mutation is responsible for most cases of a given hereditary disease. The most commonly accepted theory explaining the spread of a mutation among a population is that of the founder’s effect: a


mutation carried initially by one ancestor has been passed on from generation to generation. It is easier to observe a founder's effect when the neomutation rate of the genetic trait is low, the original population is small, and its composi- tion has undergone little change. Thus, founders' effects are mainly observed in insular populations. In Iceland, a BRCA2 mutation is responsible for most cases of predisposition to breast cancer6' Among the Ashkenazi Jewish population, an example of genetic isolation caused by cultural boundaries rather than geo- graphic ones, the three most common mutations, BRCAl/185delAG, 5382insC, and BRCA2/6174delTT, may account for 60% of ovarian cancer cases and 30% of breast cancer cases that occur in women under age 40.'

ACKNOWLEDGMENTS

The authors are grateful to Isabelle Eughe for her daily and efficient support in the organization of the genetic clinic. They are also very grateful to Francoise Smadja for having sifted through her archives to find the letter of testimony shown in Figure 3. They are profoundly indebted to Anne de Henning for the translation of the manuscript and her useful comments. They acknowledge the Institut Curie Breast Cancer Group for its contribution to the development of the Institut Curie breast cancer genetic clinic.

References

1. Abeliovich D, Kaduri L, Lerer I, et al: The founder mutations 185delAG and 5382insC in BRCAl and 6174delT in BRCA2 appear in 60% of ovarian cancer and 30% of early- onset breast cancer patients among Ashkenazi women. Am J Hum Genet 60:505, 1997

2. Agnarsson BA, Jonasson JG, Bjomsdottir IB, et al: Inherited BRCA2 mutation associated with high grade breast cancer. Breast Cancer Res Treat 4721, 1998

3. American Society of Clinical Oncology: Statement of the American Society of Clinical Oncology: Genetic testing for cancer susceptibility. JAMA 14:1730, 1996

4. American Society of Human Genetics Social Issues Subcommittee on Familial Disclo- sure: ASHG statement. Professional disclosure of familial genetic information. Am J Hum Genet 62474, 1998

5. Ansquer Y, Gautier C, Fourquet A, et al: Survival in early-onset BRCAl breast-cancer patients. Lancet 352:541,1998

6. Athma P, Rappaport R, Swift M Molecular genotyping shows that ataxia-telangiectasia heterozygotes are predisposed to breast cancer. Cancer Genet Cytogenet 92:130, 1996

7. Bsrresen AL, Andersen TI, Garber J, et al: Screening for germ line TP53 mutations in breast cancer patients. Cancer Res 523234, 1992

8. Breast Cancer Linkage Consortium: Pathology of familial breast cancer: Differences between breast cancers in carriers of BRCAl or BRCA2 mutations and sporadic cases. Lancet 349:1505, 1997

8a. Breast Cancer Linkage Consortium: Int J Cancer, in press 9. Breast Cancer Information Core (BIC) [data base online]. http://www.nhgri.nih.gov/

Intramural-research/Lab-transfer /Bic/ 10. Burke W, Daly M, Garber J, et al: Recommendations for follow-up care of individuals

with an inherited predisposition to cancer. 11. BRCAl and BRCAZ. Cancer Genetics Studies Consortium. JAMA 277:997, 1996

11. Callebaut I, Momon JP: From BRCAl to RAPI: A widespread BRCT module closely associated with DNA repair. FEBS Lett 400:25, 1997

12. Claus EB, Risch NJ, Thompson W D Genetic analysis of breast cancer in the cancer and steroid hormone study. Am J Hum Genet 48:232, 1991

13. Claus EB, Schildkraut J, Iversen ES, et a1 Effects of BRCAl and BRCA2 on the association between breast cancer risk and family history. J Natl Cancer Inst 90:1824, 1998


14. Couch FJ, Weber BL: Mutations and polymorphisms in the familial early-onset breast

15. Easton DF, Bishop DT, Ford D, et al: Genetic linkage analysis in familial breast and

16. Easton DF, Ford D, Bishop DT, and the Breast Cancer Linkage Consortium: Breast and

17. Easton DF: Breast cancer genes-what are the real risks? Nat Genet 16:210, 1997 18. Eisinger F, Alby N, Bremond A, et a1 Recommendations for medical management of

hereditary breast and ovarian cancer: The French National Ad Hoc Committee. Ann Oncol 9:939, 1998

19. Eisinger F, Jacquemier J, Charpin C , et al: Mutations at BRCA1: The medullary breast carcinoma revisited. Cancer Res 58:1588, 1998

20. Eisinger F, Stoppa-Lyonnet D, Longy M, et al: Germline mutation at BRCAl affects the histoprognostic grade in hereditary breast cancer. Cancer Res 56:471, 1996

21. Fisher 8, Costantino JP, Wickerham DL, et al: Tamoxifen for prevention of breast cancer: Report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst 90:1371, 1998

22. Ford D, Easton DF, Bishop DT, et al: Breast Cancer Linkage Consortium. Risks of cancer in BRCAl-mutation carriers. Lancet 343:692, 1994

23. Ford D, Easton DF, Stratton M, et al: Breast Cancer Linkage Consortium. Genetic Heterogeneity and Penetrance Analysis of the BRCAl and BRCA2 Genes in Breast Cancer Families. Am J Hum Genet 62676, 1998

24. Foulkes WD, Wong N, Brunet JS, et al: Germ-line BRCAl mutation is an adverse prognostic factor in Ashkenazi Jewish women with breast cancer. Clin Cancer Res 39465, 1997

25. Frank TS, Manley SA, Olopade 01, et al: Sequence analysis of BRCAl and BRCA2: Correlation of mutations with family history and ovarian cancer risk. J Clin Oncol 162417, 1998

26. Gayther SA, Warren W, Mazoyer S, et al: Germline mutations of the BRCAl gene in breast and ovarian cancer families provide evidence for a genotype-phenotype correlation. Nat Genet 11:428, 1995

27. Geller G, Botkin JR, Green MJ, et al: Genetic testing for susceptibility to adult-onset cancer. The process and content of informed consent. JAMA 2771467, 1997

28. Hall JM, Lee MK, Newman B, et al: Linkage of early onset familial breast cancer to chromosome 17q21. Science 250:1684, 1990

29. Holzman NA, Watson MS, Bar PA: The task force on genetic testing: Promoting safe and effective genetic testing in the United States: Principles and recommendations. Available at: http://wwZ.rned.jhu.edu/tfgtelsi

30. Jacquemier J, Eisinger F, Bimbaum D, et al: Histoprognostic grade in BRCAl-associated breast cancer. Lancet 345:1503, 1995

31. Janin N, Andrieu N, Ossian K, et al: Breast cancer in ataxia telangiectasia (AT) heterozygotes: Haplotype studies in French AT families. Br J Cancer 80:1042, 1999

32. Johannsson OT, Idvall I, Anderson C, et al: Tumour biological features of BRCAl induced breast and ovarian cancer. Eur J Cancer 33:362, 1997

33. Karp SE, Tonin PN, Begin LR, et al: Influence of BRCAl mutations on nuclear grade and estrogen receptor status of breast carcinoma in Ashkenazi Jewish women. Cancer 80:435, 1997

34. Kerangueven F, Essioux L, Dib A, et al: Loss of heterozygosity and linkage analysis in breast carcinoma: Indication for a putative third susceptibility gene on the short arm of chromosome 8. Oncogene 10:1023, 1995

35. Lakhani SR, Jacquemier J, Sloane JP, et al: Pathology of familial breast cancer (11): Multifactorial analysis of morphological differences between breast cancers due to BRCA1, BRCA2 and controls. J Natl Cancer Inst 90:1138, 1998

36. Lee JS, Wacholder S, Struewing JP, et al: Survival after breast cancer in Ashkenazi Jewish BRCAl and BRCA2 mutation carriers. J Natl Cancer Inst 91:259, 1999

37. Li FP, Fraumeni JF, Mulvihill JJ, et al: A cancer family syndrome in twenty-four kindreds, Cancer Res 48:5358, 1988

cancer BRCAl gene. Breast Cancer Information Core. Hum Mutat 8:8, 1996

ovarian cancer: Results from 214 families, Am J Hum Genet 52678, 1993

ovarian cancer incidence in BRCAl-mutation carriers. Am J Hum Genet 56265, 1995


38. Liaw D, Marsh DJ, Li J, et al: Germline mutations of the ?TEN gene in Cowden disease, an inherited breast and thyroid cancer syndrome. Nat Genet 1664, 1997

39. Lloyd KM, Dennis M: Cowden’s disease: A possible new symptom complex with multiple system involvement. Ann Intern Med 58:136, 1963

40. Malkin D, Li FP, Strong LC, et al: Germ-line p53 mutations in a familial syndrome of breast cancer, sarcomas and other neoplasms. Science 250:1233, 1990

41. McKinnon WC, Baty BJ, Bennett RL, et al: Predisposition genetic testing for late-onset disorders in adults. A position paper of the National Society of Genetic Counselors. JAMA 278:1217, 1997

42. Miki Y, Swensen J, Shattuck-Eidens D, et a1 A strong candidate for the breast and ovarian cancer susceptibility gene BRCAl. Science 266:66, 1994

43. Narod SA, Feunteun J, Lynch HT, et al: Familial breast-ovarian cancer locus on chromosome 17q12-q23. Lancet 338:82, 1991

44. Narod SA, Goldgar D, Cannon-Albright L, et al: Risk modifiers in carriers of BRCAl mutations. Int J Cancer 64:394, 1995

45. Offit K, Brown K: Quantitative familial cancer risk A resource for clinical oncologists. J Clin Oncol 12:1724, 1994

46. Petrij-Bosch A, Peelen T, van Vliet M, et al: BRCAl genomic deletions are major founder mutations in Dutch breast cancer patients. Nat Genet 17:341, 1997

47. Porter DE, Dixon M, Smyth E, et al: Breast cancer survival in BRCAl carriers. Lancet 341:184, 1993

48. Puget N, Siilnikova OM, Stoppa-Lyonnet D, et al: An Alu-mediated 6-kb duplication in the BRCAl gene: A new founder mutation? Am J Hum Genet 64:300,1999

49. Puget N, Stoppa-Lyonnet D, Sifiilnikova OM, et al: Screening for germ-line rearrangements and regulatory mutations in BRCAl led to the identification of four new deletions. Cancer Res 59:455, 1999

50. Puget N, Torchard D, Serova-Sinilnikova OM, et al: A 1-kb Alu-mediated germ-line deletion removing BRCAl exon 17. Cancer Res 57828, 1997

51. Robson M, Gilewski T, Haas B, et al: BRCA-associated breast cancer in young women. J Clin Oncol 16:1642, 1998

52. Savitsky K, Bar-Shira A, Gilad S, et al: A single ataxia telangiectasia gene with a product similar to PI-3 kinase. Science 268:1749, 1995

53. Seitz S, Rohde K, Bender E, et al: Strong indication for a breast cancer susceptibility gene on chromosome 8p12-p22: Linkage analysis in German breast cancer families. Oncogene 14741,1997

54. Sidransky D, Tokino T, Helzlouer K, et al: Inherited p53 gene mutations in breast cancer. Cancer Res 52:2984, 1992

55. Smith SA, Easton DF, Evans DG, et al: Allele losses in the region 17q12-21 in familial breast and ovarian cancer involve the wild-type chromosome. Nat Genet 2:128, 1992

56. Starink TM, van der Veen JPW, Arwert F, et al: The Cowden syndrome: A clinical and genetic analysis study in 21 patients. Clin Genet 29222, 1986

57. Stoppa-Lyonnet D, Laurent-Puig P, Essioux L, et al: BRCAl sequence variations in 160 individuals referred to a breast/ovarian family cancer clinic. Am J Hum Genet 60:1021, 1997

58. Struewing JP, Hartge P, Wacholder S, et al: The risk of cancer associated with specific mutations of BRCAl and BRCA2 among Ashkenazi Jews. N Engl J Med 3363401,1997

59. Swift M, Morrell D, Massey RB, et al: Incidence of cancer in 161 families affected by ataxia-telangiectasia. N Engl J Med 325:1831, 1991

60. Tavtigian SV, Simard J, Rommens J, et al: The complete BRCA2 gene and mutations in chromosome 13q-linked kindreds. Nat Genet 12:333, 1996

61. Thorlacius S, Olafsdottir G, Tryggvadottir L, et al: A single BRCA2 mutation in male and female breast cancer families from Iceland with varied cancer phenotypes. Nat Genet 13:117, 1996

62. Thorlacius S, Struewing JP, Hartge P, et al: Population-based study of risk of breast cancer in carriers of BRCA2 mutation. Lancet 352:1337-1339, 1998

63. Vasen HF, Haites NE, Evans DG, et al: Currenkpolicies for surveillance and management in women at risk of breast and ovarian cancer: A survey among 16 European


familv cancer clinics. European Familial Breast Cancer Collaborative Group. Eur J Can& 34:1922, 1998

64. Verhooe LC. Brekelmans CTM, Sevnaeve C, et al: Survival and tumour characteristics of breast-cancer patients with germline mutations of BRCA1. Lancet 351:316, 1998

65. Watson P, Marcus JN, Lynch HT Prognosis of BRCAl hereditary breast cancer. Lancet 351:304, 1998

66. Wooster R, Bignell G, Lancaster J, et al: Identification of the breast cancer susceptibility gene BRCA2. Nature 378:789, 1995

67. Wooster R, Neuhausen S, Mangion J, et al: Localization of a breast cancer susceptibility gene, BRCA2, to chromosome 13q12-13. Science 265:2088, 1994

68. Zhang H, Tombline G, Weber B: BRCA1, BRCA2, and response: Collision or collusion? Cell 92433, 1998

Address reprint requests to Dominique Stoppa-Lyonnet, MD, PhD

Service de GenCtique Oncologique Institut Curie 26 Rue d’Ulm

F75248 Paris Cedex 5 France

e-mail: dominique.lyonnet8curie.net

Documents

GENETIC TESTING FOR BREAST CANCER PREDISPOSITION