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LETTER TO THE EDITOR Early Impact of Mammographic Screening in Western Siberia To the Editor: In most countries nowadays, breast cancer is the most common cancer in the female population. As in most cancers, there is a strong association of the stage disease with both overall and free-disease survival after adequate treatment. Thus, early diagnosis of these tumors has strong potential to decrease mortal- ity from the disease. In the randomized trials, a signifi- cant 20% decrease in breast cancer mortality was observed among all invited to screening (attendees and nonattendees). The reduction is likely to be of the order of 30% among women who underwent mammography screening regularly (2,3,5). In Khanty-Mansiysky Autonomous Okrug Ugra, Russian Federation, breast cancer is the most common cancer tumor among female population during the last 10 years. In 2007 the Breast Cancer Screening Pro- gram (BCSP) was implemented in Ugra (6). The BCSP in Ugra covers the female population aged over 40 years, with two-view mammography examination (MLO and CC). The screening interval is 2 years, and single reading is the standard. Data on screening are obtained every year from the annual reports for the State Healthcare Department. The form for that annual report has been created by the authors for the BCSP. The information on the female population, all newly diagnosed breast cancer cases and deaths due to breast cancer in Ugra was obtained from State Cancer Registry for the period 20022011. Statistical analysis was carried out using Poisson regression, on four endpoints in turn: breast cancer incidence, breast can- cer mortality, incidence of node positive breast cancer and incidence of invasive breast cancers of size greater than 20 mm. We tested for a significant difference in average incidence between the prescreening years (20022006) and the screening (20072011), adjusting for the trend in the prescreening years, and for a change in the trend between prescreening and screen- ing years. We also calculated the expected values for the four endpoints based on the trends in the presc- reening years, and compared these with the observed values. Overall, 56.2% of the target population (186,460) has been screened at least once. 460 breast cancer cases were diagnosed within the first round and 22 cases during the second round of screening. Incidence of cancers was increasing in the prescreening years and continued to do so at the same rate in the screening. There was no significant difference in average inci- dence between the two screening periods (p = 0.1) or any change in the trend between the pre and postsc- reening periods (p = 0.6). There was a significant change in the trend in incidence of node positive dis- ease (p = 0.007) between the prescreening and screen- ing periods, with an increasing trend in the prescreening period which was no longer present in the screening years (Fig. 1). Based on the prescreening trend, the expected number of node positive cancers in the screening period was 1,197, whereas the observed number was 848, a deficit of 29%. The corresponding results for incidence of cancers of size greater than 20 mm shows a reduction in the average incidence of tumors >20 mm in the screening period, taking account of the trend in the prescreening, of borderline significance (p = 0.06). There were 1,240 such cancers in the screening period compared with 1,595 expected, a reduction of 24%. The estimation of the observed and expected breast cancer deaths from the trend in mortality up to 2006 indicates a reduction in deaths in the screening period, taking account of the prescreen- ing trend. The difference was not significant (p = 0.9), nor was there a significant change in the trend in the screening period (p = 0.3). There were 542 breast can- cer deaths in years 20072011 compared with 614 expected, a nonsignificant 12% reduction. Our results indicate that the incidence of node posi- tive breast cancer has declined significantly following Address correspondence and reprint requests to: Professor Natalia Zakharova, PhD, MD, Department of Oncology and Radiology, Khanty-Mansiysk State Medical Academy, Mira 40, Khanty-Mansiysky Auton- omous OkrugUgra, Khanty-Mansiysk 628012, Russian Federation, or e-mails: [email protected] and [email protected] DOI: 10.1111/tbj.12248 © 2014 Wiley Periodicals, Inc., 1075-122X/14 The Breast Journal, Volume 20 Number 2, 2014 219–220

Early Impact of Mammographic Screening in Western Siberia

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Page 1: Early Impact of Mammographic Screening in Western Siberia

LETTER TO THE EDITOR

Early Impact of Mammographic Screening in WesternSiberia

To the Editor:

In most countries nowadays, breast cancer is the

most common cancer in the female population. As in

most cancers, there is a strong association of the stage

disease with both overall and free-disease survival

after adequate treatment. Thus, early diagnosis of

these tumors has strong potential to decrease mortal-

ity from the disease. In the randomized trials, a signifi-

cant 20% decrease in breast cancer mortality was

observed among all invited to screening (attendees and

nonattendees). The reduction is likely to be of the

order of 30% among women who underwent

mammography screening regularly (2,3,5).

In Khanty-Mansiysky Autonomous Okrug – Ugra,

Russian Federation, breast cancer is the most common

cancer tumor among female population during the last

10 years. In 2007 the Breast Cancer Screening Pro-

gram (BCSP) was implemented in Ugra (6). The BCSP

in Ugra covers the female population aged over

40 years, with two-view mammography examination

(MLO and CC). The screening interval is 2 years, and

single reading is the standard. Data on screening are

obtained every year from the annual reports for the

State Healthcare Department. The form for that

annual report has been created by the authors for the

BCSP. The information on the female population, all

newly diagnosed breast cancer cases and deaths due to

breast cancer in Ugra was obtained from State Cancer

Registry for the period 2002–2011. Statistical analysiswas carried out using Poisson regression, on four

endpoints in turn: breast cancer incidence, breast can-

cer mortality, incidence of node positive breast cancer

and incidence of invasive breast cancers of size greater

than 20 mm. We tested for a significant difference in

average incidence between the prescreening years

(2002–2006) and the screening (2007–2011), adjustingfor the trend in the prescreening years, and for a

change in the trend between prescreening and screen-

ing years. We also calculated the expected values for

the four endpoints based on the trends in the presc-

reening years, and compared these with the observed

values.

Overall, 56.2% of the target population (186,460)

has been screened at least once. 460 breast cancer

cases were diagnosed within the first round and 22

cases during the second round of screening. Incidence

of cancers was increasing in the prescreening years and

continued to do so at the same rate in the screening.

There was no significant difference in average inci-

dence between the two screening periods (p = 0.1) or

any change in the trend between the pre and postsc-

reening periods (p = 0.6). There was a significant

change in the trend in incidence of node positive dis-

ease (p = 0.007) between the prescreening and screen-

ing periods, with an increasing trend in the

prescreening period which was no longer present in the

screening years (Fig. 1). Based on the prescreening

trend, the expected number of node positive cancers in

the screening period was 1,197, whereas the observed

number was 848, a deficit of 29%. The corresponding

results for incidence of cancers of size greater than

20 mm shows a reduction in the average incidence of

tumors >20 mm in the screening period, taking

account of the trend in the prescreening, of borderline

significance (p = 0.06). There were 1,240 such cancers

in the screening period compared with 1,595 expected,

a reduction of 24%. The estimation of the observed

and expected breast cancer deaths from the trend in

mortality up to 2006 indicates a reduction in deaths in

the screening period, taking account of the prescreen-

ing trend. The difference was not significant (p = 0.9),

nor was there a significant change in the trend in the

screening period (p = 0.3). There were 542 breast can-

cer deaths in years 2007–2011 compared with 614

expected, a nonsignificant 12% reduction.

Our results indicate that the incidence of node posi-

tive breast cancer has declined significantly following

Address correspondence and reprint requests to: Professor Natalia

Zakharova, PhD, MD, Department of Oncology and Radiology,

Khanty-Mansiysk State Medical Academy, Mira 40, Khanty-Mansiysky Auton-

omous Okrug–Ugra, Khanty-Mansiysk 628012, Russian Federation, or

e-mails: [email protected] and [email protected]

DOI: 10.1111/tbj.12248

© 2014 Wiley Periodicals, Inc., 1075-122X/14The Breast Journal, Volume 20 Number 2, 2014 219–220

Page 2: Early Impact of Mammographic Screening in Western Siberia

the introduction of mammographic screening in Khan-

ty-Mansiysky Autonomous Okrug. There was a bor-

derline significant reduction in rates of invasive

tumors of size greater than 20 mm. The reductions in

node positive and large tumors are consistent with the

findings of the Swedish organized Screening Evalua-

tion Group (7). No significant reduction in breast can-

cer mortality has been observed, which is to be

expected in the first 5 years of the program. Most of

the deaths from breast cancer in the first 5 years will

be from cancer diagnosed before the screening started

(5). The reduction in node positive disease, however,

suggests that a significant mortality reduction will be

observed in the future. In the randomized trials of

breast screening, the reductions in node positive can-

cer incidence closely approximated the reductions in

breast cancer mortality (1,3). We found no significant

increase in incidence with the introduction of screen-

ing. This suggests that there is no substantial overdiag-

nosis in this program.

In terms of research, the main target for the future

is further observation of breast cancer incidence and

mortality. In addition, more detailed analysis is indi-

cated of the individual cancers, in terms of screening/

symptomatic status, prognostic features, and mortal-

ity. It should be noted that this work is aimed not at

the efficacy of screening in principle, which is a matter

for the trials, but at evaluation of this particular

screening program. In clinical terms, since the findings

to date suggest a benefit of the screening, the main

aim should be to improve coverage of the population

with screening.

In conclusion, mammographic screening in Khanty-

Mansiysky Autonomous Okrug has been associated

with a significant reduction in node positive breast

cancers, taking account of prescreening trends. It is

likely that a corresponding significant mortality reduc-

tion will emerge in the future. Careful follow-up of

the population should continue.

Natalia Zakharova, PhD, MD*

Stephen Duffy, MSc†

*Department of Oncology and Radiology

State Khanty-Mansiysk Medical Academy

Khanty-Mansiysk

Russian Federation

and †Centre for Cancer Prevention

Wolfson Institute of Preventive Medicine

Barts and The London School of Medicine and Dentistry

Queen Mary University of London

London

UK

REFERENCES

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Gr€ontoft O. Update of the Swedish two-country program of mam-

mographic screening for breast cancer. Radiol Clin North Am1992;1:187–209.

2. Tabar L, Vitak B, Chen THH, et al. Swedish Two-County

Trial: impact of mammographic screening on breast cancer mortal-

ity during 3 decades. Radiology 2011;260:658–63.3. Smith RA, Duffy SW, Gabe R, Tabar L, Yen AM, Chen TH.

The randomized trials of breast cancer screening: what have we

learned? Radiol Clin N Am 2004;42:793–806.4. Moss SM, Cuckle H, Evans A, Johns L, Waller M, Bobrow

L. Effect of mammographic screening from age 40 years on breast

cancer mortality at 10 years’ follow-up: a randomised controlled

trial. Lancet 2006;368:2053–60.5. Duffy SW, Tabar L, Chen HH, et al. The impact of organized

mammography service screening on breast cancer mortality in seven

Swedish counties: a collaborative evaluation. Cancer 2002;95:458–69.6. Zakharova NA, Duffy SW, Mackay J, Kotlyarov E. The

introduction of a breast cancer screening programme in a region of

medium-risk for breast cancer: in Khanty-Mansiysky Autonomous

Okrug – Ugra (Russian Federation). Ecancermedicalscience 2011.Article Number: 195. Doi: 10.3332/ecancer.2011.195

7. Swedish Organised Service Screening Evaluation Group.

Effect of mammographic service screening on stage at presentation

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Figure 1. Observed incidence of node positive breast cancer in

Ugra, ages 40 +, and incidence expected on the basis of the trend

in 2002–2006.

220 • letter to the editor