Gynecologic Oncology 114 (2009) 246–252

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Gynecologic Oncology

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Extreme drug resistance assay results do not influence survival in women withepithelial ovarian cancer

Amer K. Karam a,⁎, Jing Wang Chiang b, Ewina Fung c, Vladimir Nossov a, Beth Y. Karlan d

a Division of Gynecologic Oncology, The David Geffen School of Medicine at UCLA, 10833 Le Conte Ave, Los Angeles, CA 9095, USAb Department of Obstetrics and Gynecology, Santa Clara Valley Medical Center, 751 S. Bascom Ave, San Jose, CA 95128, USAc Department of Obstetrics and Gynecology, Cedars-Sinai Medical Center, 8700 Beverly Blvd, Los Angeles, CA 90048, USAd Women's Cancer Research Institute, Cedars-Sinai Medical Center, 8700 Beverly Blvd, Los Angeles, CA 90048, USA

⁎ Corresponding author. Fax: +1 310 794 3670.E-mail address: akaram@mednet.ucla.edu (A.K. Kara

0090-8258/$ – see front matter © 2009 Elsevier Inc. Adoi:10.1016/j.ygyno.2009.02.022

a b s t r a c t

a r t i c l e i n f o

Article history:

Objectives. Extreme drug Received 17 January 2009Available online 4 June 2009

Keywords:Ovarian cancerNeoplasm drug resistanceAdjuvant chemotherapyCytoreductive surgery

resistance (EDR) assays have been used to identify chemotherapy regimens thatare least likely to be of clinical benefit in the treatment of epithelial ovarian cancer (EOC). We sought toexamine the impact of EDR assay-guided therapy on the outcome of patients with EOC in the primary andrecurrent settings.

Methods. We conducted a retrospective review of demographic, pathologic, EDR assay and clinicaloutcome data from 377 patients with EOC who had an assay sent at the time of their primary or subsequentcytoreductive surgeries. Multivariate analyses were performed using Cox proportional hazards method toidentify and estimate the impact of independent prognostic factors on time to progression (TTP), overallsurvival (OS) and survival after recurrence (RS).

Results. Increasing age was associated with a worse OS and RS (HR=1.34; 95% CI, 1.14–1.58 andHR=1.14; 95% CI, 1.00–1.31, respectively for each decade increase in age). Surgical outcome in the setting ofprimary or secondary cytoreduction remained an important predictor of survival. Compared with patientswith microscopic residual disease, patients who were left with 0.1 to 1.0 cm and N1.0 cm residual disease hadan increased risk of recurrence (HR=1.94; 95% CI, 1.33 to 2.84 and HR=3.61; 95% CI; 2.07 to 6.39,respectively) and death (HR=1.59; 95% CI, 1.03 to 2.45; and HR=2.14; 95% CI, 1.09 to 4.20, respectively). Forpatients who recurred, those who did not undergo secondary cytoreductive surgery and patients who wereleft with N1.0 cm residual had an increased risk of death compared to patients with microscopic residual(HR=2.13; 95% CI, 1.28 to 3.54; and HR=2.84; 95% CI, 1.71 to 4.71, respectively). EDR assay results analyzedfor single agents or combinations of chemotherapies failed to independently predict patient outcomes nomatter if the assay was performed at the time of the primary surgery or recurrence.

Conclusion. EDR assay results do not independently predict or alter the outcomes of patients with EOCwho are treated with the current standards of primary cytoreductive surgery followed by platinum andtaxane combination chemotherapy.

© 2009 Elsevier Inc. All rights reserved.

Introduction

Ovarian cancer is the most lethal gynecologic malignancy in theUnited States accounting for an estimated 15,520 deaths in 2008 [1].With an annual incidence of 21,650 cases, the majority of patientspresent with advanced stage disease [1]. Although, aggressive surgicalresection and platinum/taxane combination chemotherapy haveresulted in improved outcomes, the majority of patients withadvanced stage disease will eventually suffer from a recurrence oftheir disease. The optimal regimen for the treatment of patients withrecurrent epithelial ovarian cancer (EOC) has not been clearly defineddue to the limited effectiveness and equivalence of second-line agents,

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ll rights reserved.

as well as the significant heterogeneity in the individual responses tochemotherapy [2]. Patients who relapse after an initial treatment-freeinterval ≤6 months from the end of their platinum-based primarychemotherapy are considered to have platinum resistant (PR) diseasewhereas patients who have relapsed after a treatment-free intervalN6 months are deemed to be platinum-sensitive (PS) [3]. Patientswith a prolonged treatment-free interval (N12 months), in generalrespond better to second-line chemotherapy and have a morefavorable prognosis [4,5].

Chemotherapy sensitivity and resistance assays have receivedconsiderable interest over the past three decades as a tool to helprefine and improve the choice of chemotherapy regimens [6]. Kernand Weisenthal developed an assay that predicts extreme drugresistance (EDR) to chemotherapy in a number of solid tumors [7]. Inthis assay, human tumor cells are cultured in soft agar and exposed to

Table 1Demographic and clinical characteristics of the study population.

Demographics Frequency Percent

Age, yearsMedian 59.0Range 24.4–89.1

RaceCaucasian 315 87.7African American 21 5.8Hispanic 18 5.0Asian 5 1.4

Residual disease at PCRSa

Microscopic 76 29.90.1–1 cm 145 57.1≥1 cm 33 13.0

FIGO stageI 22 6.6II 12 3.6III 262 78.4IV 38 11.4

Tumor grade1 11 3.92 14 4.93 260 91.2

HistologyPapillary serous 265 77.9Mucinous 7 2.1Clear cell 15 4.4Endometrioid 13 3.8Mixed 25 7.4Undifferentiated 15 4.4

Primary chemotherapyPlatinum and taxane 231 88.8Platinum and cyclophosphamide 16 6.2Platinum 5 1.9Platinum and other 3 1.2Taxane alone 3 1.2CAP 1 0.4Other 1 0.4

SCRSb

No 93 36.0Yes 165 64.0

Recurrence typePlatinum resistant (PR) 75 29.4Platinum sensitive (PS) 180 70.6

Residual disease at SCRSMicroscopic 63 42.60.1–1 cm 55 37.2≥1 cm 30 20.3

StatusNED 85 22.8AWD 28 7.5DOD 251 67.3DOC 9 2.4

a PCRS: primary cytoreductive surgery.b SCRS: secondary cytoreductive surgery.

247A.K. Karam et al. / Gynecologic Oncology 114 (2009) 246–252

drugs at high concentrations for long exposure times. The in vitroconcentration by exposure time values are typically more than 100times higher than those expected with conventional chemotherapy inthe clinical setting. Tumor cells that survive during this overwhelmingdrug exposure show “extreme drug resistance”. The authors statedthat this type of assay has a negative predictive value of greater than99%, such that ineffective chemotherapies can be confidentlyeliminated from a patient's drug regimen [7].

Commercially available in vitro EDR assays have been examined todetermine their usefulness as a tool to identify those agents that haveless than a 3% chance of clinical benefit [7]. Although a number ofstudies have examined the technical aspects of resistance assays andthe correlation of the assay results with clinical outcomes, little datahas been published on the clinical outcomes of patients treated basedon the assay results versus those for whom chemotherapy wasprescribed based on clinical standards of care [6,8,9]. In their lastTechnology Assessment, the American Society of Clinical Oncologyevaluated the evidence from published clinical trials that testedwhether performance of chemotherapy sensitivity or resistanceassays improves patient outcomes compared with empirical selectionof chemotherapy regimens based on published clinical trials. TheWorking Group found no prospective randomized studies focusing onthe use of the EDR and concluded that available evidence isinsufficient to recommend routine use of these assays [6,9].

The purpose of our study was to examine the effect of EDR assay-guided therapy on the outcome of patients with EOC in the primaryand recurrent setting.

Materials and methods

The current study was a retrospective review, under an IRB-approved protocol, of the records from all patients with invasive EOCwho underwent in vitro EDR assays and were treated at Cedars-SinaiMedical Center between October 1995 and April 2005.

Clinical parameters including age at diagnosis, race, stage ofdisease, tumor grade, cell type, extent of surgical debulking, primarychemotherapies and the number and dates of all subsequentcytoreductive surgeries for recurrent disease were extracted bymedical record review. The stage at initial diagnosis was based onthe system developed by the International Federation of Gynecologyand Obstetrics (FIGO). The amount of residual disease at the time ofsurgery was divided into microscopic, 0.1–1.0 cm, and N1.0 cm. Clear-cell carcinomas were assigned a pathology grade of 3 and lowmalignant potential tumors were excluded.

The EDR assays were performed at the discretion of the individualgynecologic oncologist and/or medical oncologist. A viable tumor ormalignant fluid specimen was obtained and submitted in transportmedia to Oncotech, Inc. (Irvine, CA). The tritiated thymidine uptakedrug resistance assay procedures were performed according topreviously published protocols [7,10]. The degree of in vitro drugresistance to tumor specimens was stratified among three categories.Low drug resistance (LDR) was said to exist when the assay resultafter exposure to a given drug was greater than the median percentcell inhibition; EDR existed when the assay result was less than themedian percent cell inhibition minus 1 standard deviation (SD), andintermediate drug resistance (IDR) existed when the assay result wasbetween LDR and EDR.

At our institution, candidates for secondary cytoreductive surgery(SCRS) usually have an initial progression-free survival (PFS) of atleast 6 months, less than 3 sites of recurrence and a favorableperformance status [11,12]. Patients with recurrent EOC who did notundergo additional cytoreductive surgery could have EDR assays sentbased on malignant pleural or peritoneal fluid.

The primary end points were time to progression (TTP), overallsurvival (OS) and survival after recurrence (RS). TTP was calculatedfrom the date of diagnosis to the date of disease recurrence, death, or

most recent follow-up visit. OS was calculated from the date ofdiagnosis to the date of death or last contact. RS was calculated fromthe date of first recurrence to the date of death or last contact.

Kaplan–Meier survival curves for the various clinical, laboratoryand pathologic variables were calculated and compared using the log-rank test. Multivariate analyses were performed with the use of Coxproportional hazards method to identify the independent prognosticfactors as well as to estimate their impact on TTP, OS and RS adjustedfor the other covariates. All statistical tests were two-tailed with asignificance level set at 0.05. All statistical analyses were performedusing SPSS version 15.0 for Windows (SPPS Inc., Chicago, IL).

Results

Three hundred seventy-seven patients with invasive EOC, who hadan EDR assay performed, were identified. All patients were seen atCedars-Sinai Medical Center. Table 1 summarizes the demographic

Table 3Univariate analysis of OS and TTP.

Univariate analysis OS TTP

Characteristic Median(months)

p Median(months)

p

Age group, yearsb40 153.9 b0.001 49.2 0.00840–50 59.5 33.850–60 59.5 26.060–70 46.3 19.5N70 42.5 19.9

Stageb III 88.8 0.002 55.5 b0.001≥ III 48.6 21.3

RaceNon-Hispanic Caucasian 53.9 0.3 26.0 0.2Other 51.1 13.7

Residual disease at primary surgeryMicroscopic 66.8 0.03 37.0 b0.0010.1–1.0 cm 45.0 19.0N1.0 cm 39.5 10.2

Grade1 133.7 0.005 100.0 0.0082 or 3 45.0 20.7

HistologyPapillary serous 52.1 0.8 23.9 0.4Other 53.2 26.0

Primary chemotherapyPlatinum and taxane 51.7 0.03 32.2 0.3Other 74.7 22.5

EDR assay at primary surgeryNo 61.9 0.002 27.0 0.1Yes 44.1 23.7

Carboplatin EDRNo 51.7 0.7 26.0 0.5Yes 57.1 25.6

Cisplatin EDRNo 58.1 0.4 25.6 0.8Yes 47.9 21.8

248 A.K. Karam et al. / Gynecologic Oncology 114 (2009) 246–252

and clinical characteristics of the study population. The median agewas 59 years (range, 24 to 89 years) and 88% of patients were non-Hispanic Caucasian. Not all patients had their primary surgery bygynecologic oncologists. The tumor was completely resected in 30% ofpatients. In 57% there was 0.1 to 1.0 cm residual and only 13% had atumor residual of N1.0 cm after primary cytoreductive surgery. Sevenpercent of patients had FIGO stage I disease, 4% had stage II, 78% hadstage III and 11% had stage IV disease. Seventy-eight percent ofpatients had papillary serous histology and 91% had poorly differ-entiated tumors. Eighty-nine percent of patients received platinumand taxane based chemotherapy in the adjuvant setting. Two hundredand ninety-nine (80%) patients recurred and 251 (67%) patients diedfrom their disease during a median follow-up period of 59 months.Among those patients who suffered from a recurrence, 29% had PRdisease and 71% had PS disease. One hundred and sixty five (64%)patients underwent a secondary cytoreductive surgery. In 43% of thosepatients, secondary cytoreductive surgery successfully reduced tumorburden to microscopic residual disease, 37% were left with 0.1 to1.0 cm tumor residual and 20% with N1.0 cm tumor residual. Overall,the median TTP was 24.8 months (95% CI, 20.7 to 28.9 months), themedian OS was 53.0 months (95% CI, 46.9 to 59.0 months) and themedian RS was 22.3 months (95% CI, 19.5 to 25.1 months).

EDR assay results

Table 2 shows the results of the EDR assays. Sixty four percent ofpatients (N=217) had an EDR assay sent at the time of their primarycytoreductive surgery. Sixty three percent of patients who sufferedfrom a recurrence of their disease (N=160) had an EDR assay sent.Fifteen percent of patients (N=50) had EDR assays performed onmultiple occasions. The incidence of assay-detected EDR to cisplatinwas 16% and 18% for carboplatin. EDR was present in 16% of assayswith paclitaxel and 26%with cyclophosphamide. The incidence of EDR

Any platinum EDRNo 57.1 0.5 26.0 0.5Yes 49.3 24.7

Cyclophosphamide EDRNo 49.8 0.4 22.5 0.2Yes 53.9 27.6

Paclitaxel EDRNo 55.3 0.1 26.5 0.2Yes 36.7 18.4

Any taxane EDRNo 53.1 0.8 26.5 1.0Yes 53.9 25.6

Platinum and taxane EDRNo 53.2 0.6 26.7 0.8Yes 51.1 24.7

Carboplatin LDRNo 58.1 0.2 26.5 0.8Yes 47.9 24.7

Cisplatin LDRNo 58.1 0.4 25.6 0.8Yes 47.9 21.8

Any platinum LDRNo 52.1 0.8 26.5 0.07Yes 56.5 22.5

Cyclophosphamide LDRNo 57.1 0.06 26.2 0.1Yes 47.9 21.2

Paclitaxel LDRNo 53.1 0.6 25.6 1.0Yes 51.7 26.0

Any taxane LDRNo 55.3 0.1 26.7 0.1Yes 37.9 17.7

Platinum and taxane LDRNo 49.8 0.1 26.0 0.7Yes 58.4 26.5

Table 2EDR assay results.

Characteristic Frequency Percent

EDR assay at PCRSNo 125 36.5Yes 217 63.5

EDR assay at recurrenceNo 96 37.5Yes 160 62.5

Number of EDR assays1 292 85.42 45 13.23 4 1.24 1 0.3

EDR assay results carboplatinEDR 57 18.2IDR 101 32.3LDR 155 49.5

CisplatinEDR 52 15.8IDR+LDR 278 84.2

CyclophosphamideEDR 85 26.1IDR+LDR 241 73.9

TaxolEDR 51 15.7IDR+LDR 274 84.3

PlatinumEDR 81 23.1IDR+LDR 270 76.9

TaxaneEDR 58 17.2IDR+LDR 280 82.8

Platinum and taxane EDRNo 315 95.5Yes 15 4.5

Table 4Univariate analysis of RS.

Univariate analysis RS

Characteristic Median (months) p

Age group, yearsb40 50.6 0.00140–50 24.350–60 27.060–70 20.2N70 22.2

RaceNon-Hispanic Caucasian 23.2 0.3Other 15.7

Stageb III 28.9 0.8≥ III 22.3

HistologyPapillary Serous 21.2 0.3Other 22.4

Primary chemotherapyPlatinum and taxane 22.3 0.1Other 33.3

Initial PFS≤6 months 21.8 0.046–12 months 19.212–24 months 25.1N24 months 30.6

SCRS and residual diseaseNo SCRS 15.1 0.04SCRS and N1.0 cm residual 10.5SCRS and 0.1–1.0 cm residual 28.9SCRS and microscopic residual 33.8

EDR assay at recurrenceNo 15.7 b0.001Yes 28.6

Carboplatin EDRNo 21.8 0.5Yes 24.7

Cisplatin EDRNo 24.3 0.5Yes 20.2

Any platinum EDRNo 23.3 0.5Yes 20.4

Cyclophosphamide EDRNo 22.2 1.0Yes 23.5

Paclitaxel EDRNo 23.1 0.2Yes 18.3

Any taxane EDRNo 21.9 1.0Yes 23.2

Platinum and taxane EDRNo 22.3 0.4Yes 21.8

Carboplatin LDRNo 24.3 0.2Yes 19.6

Cisplatin LDRNo 24.3 0.5Yes 20.3

Any platinum LDRNo 21.8 0.4Yes 24.7

Cyclophosphamide LDRNo 24.7 0.3Yes 20.4

Paclitaxel LDRNo 21.8 0.9Yes 23.2

Any taxane LDRNo 23.1 0.3Yes 18.3

Platinum and taxane LDRNo 21.8 0.2Yes 23.3

249A.K. Karam et al. / Gynecologic Oncology 114 (2009) 246–252

to both a platinum and taxane chemotherapeutic agent testedseparately was only 4.5%.

Univariate analysis

Table 3 shows the median TTP and OS based on patientcharacteristics and EDR assay results. Increasing age was associatedwith decreased TTP, and OS. As expected, advanced stage and highergrade tumors were associated with a significantly shorter TTP andOS. On the other hand tumor histology and race did not appreciablyaffect TTP and OS likely reflecting the small number of patientspresent in the non-serous histology and non-Caucasian racecategories. Table 4 shows the median RS based on the attributes ofpatients who recurred as well as the results of their EDR assays. Aswith TTP and OS, increasing age was associated with shorter RS. Onthe other hand, advanced stage did not significantly affect RS,reflecting the poor prognosis once disease has recurred regardless ofinitial stage. Tumor histology did not seem to affect the median TTP,OS or RS either. Similarly race was not significantly associated withTTP, OS and RS.

Patients with microscopic residual disease after their primarycytoreductive surgery had the longest TTP and OS, 37 and 67 monthsrespectively, compared with patients left with any gross residualdisease. A difference in median RS following secondary cytoreductivesurgery based on the amount of residual disease was also evident.Patients who did not undergo a secondary cytoreductive surgery andthose patients with N1.0 cm residual disease after a secondarycytoreductive surgery had similar median RS, 15 and 11 monthsrespectively, while those patients who were left with 0.1–1.0 cm andmicroscopic residual disease had a significantly longer median RS, 29and 34 months respectively (p=0.04). Longer initial PFS was alsoassociated with longer median RS.

Platinum and taxane based primary adjuvant chemotherapy wasassociated with a shorter OS but did not affect TTP or survivalfollowing a recurrence. Patients who had an EDR assay sent with theirprimary cytoreductive surgery did not have a significantly differentTTP compared to patients who did not but they had a significantlyshorter median OS. Conversely, those patients who had an EDR assaysent at their recurrence had a significantly longer median RS,29 months, compared with those patients who did not have onesent. The results the EDR assays were not significantly associated withany differences in TTP, OS or RS, whether comparing tumors thatexhibited EDR to those with IDR and LDR or when contrasting tumorsthat exhibited LDR to those tumors with IDR and EDR.

Multivariate analysis

All variables considered as potential prognostic factors wereincluded in a Cox proportional hazards regression model to identifyindependent prognostic factors, the results of which are illustrated inTables 4 and 5.

An interval age increase of 10 years was associated with a 34%(HR=1.34; 95% CI, 1.14–1.58; p=0.001) increased risk of death overalland a 15% (HR=1.14; 95%CI,1.00–1.31;p=0.04) increased risk of deathafter recurrence but did not reach statistical significance for the risk ofprogression. Using microscopic residual disease as the referent, thehazard ratio for disease progression in patients with 0.1 to 1.0 cm andN1.0 cmwas 1.94 (95% CI, 1.33 to 2.84; p=0.001) and 3.61 (95% CI; 2.07to 6.39; pb0.001) respectively. OS also was decreased for patients with0.1 to 1.0 cm (HR=1.59; 95% CI, 1.03 to 2.45; p=0.04) and N1.0 cm(HR=2.14; 95% CI, 1.09 to 4.20; p=0.03). Using the same referent forpatients who suffered from a recurrence, those patients who did notundergo a secondary cytoreductive surgery and patients who were leftwith N1.0 cm residual demonstrated a significantly higher risk of death(HR=2.13; 95% CI,1.28 to 3.54; p=0.004 andHR=2.84; 95% CI,1.71 to4.71; pb0.001 respectively). Neither tumor grade nor advanced

Table 5Multivariate analysis of the likelihood of disease recurrence, death from disease and death from disease after recurrence.

Multivariate Analysis Disease progression Death Death after recurrence

Characteristic HR 95% CI p HR 95% CI p HR 95% CI p

Age decades 1.12 0.98 1.28 0.1 1.33 1.13 1.56 0.001 1.14 1.00 1.31 0.04StageStage b III 1.0 1.0Stage ≥ III 3.61 0.86 6.4 0.09 2.78 0.68 11.3 0.15

Tumor gradeGrade 1 1.0 1.0Grade 2 or 3 1.87 0.68 5.14 0.23 5.41 0.73 40.1 0.10

Primary surgery residual diseaseMicroscopic 1.00 1.000.1 to 1.0 cm 1.94 1.33 2.84 0.001 1.59 1.03 2.45 0.04N1.0 cm 3.61 2.07 6.29 b0.001 2.14 1.09 4.20 0.03

Adjuvant chemotherapyPlatinum and taxane 1.00Other 0.94 0.23 3.86 0.93

EDR assayNone 1.0At primary surgery 1.13 0.75 1.72 0.55At recurrence 0.83 0.55 1.27 0.40

SCRS residual diseaseMicroscopic 1.00.1 to 1.0 cm 1.14 0.74 1.77 0.55N1.0 cm 2.84 1.71 4.71 b0.001No SCRS 2.13 1.28 3.54 0.004

Initial PFSb6 months 1.006 to 12 months 1.15 0.75 1.76 0.5212 to 24 months 1.32 0.83 2.08 0.24N24 months 1.25 0.84 1.86 0.28

250 A.K. Karam et al. / Gynecologic Oncology 114 (2009) 246–252

stage disease was independently associated with TTP or OS. Similarlyincreasing PFS did not seem to affect RS. When compared to patientswho did not have an EDR assay sent at the time of their initial surgery orrecurrence and controlling for the other prognostic indicators, the use ofEDR assays and their results did not independently alter the patients'ultimate clinical outcomes.

Discussion

This study is a retrospective analysis of a large cohort of EOCpatients who had an EDR assay sent at primary cytoreductive surgeryor in the setting of recurrent disease. Our data do not demonstrate thatEDR assay results independently predict patient prognosis whencontrolling for prognostic factors known to influence patient outcome.Age and the amount of residual disease at the time of cytoreductivesurgery were statistically significant prognostic factors in the multi-variate analysis as has been previously reported [13,14]. In additionthe median TTP and OS of our study were comparable to thosereported by the Gynecologic Oncology Group in their latest retro-spective analysis of the outcome data from 1895 patients with stage IIIEOC whowere treated with platinum and paclitaxel chemotherapy onone of six of their randomized controlled trials [13]. Similarly themedian survival following recurrence was consistent with thatpreviously reported for analogous patients as well as those whounderwent secondary cytoreductive surgery [15]. The fact that stageand grade did not remain significantly associated with OS and TTP onmultivariate analysis may be due to the small number of patients inthe early stage and low grade groups, resulting in seemingly higherodds of recurrence and deaths but wide confidence intervals and pvalues that did not reach significance. The finding that on univariateanalysis combination chemotherapy using platinum and taxanechemotherapy was associated with a shorter OS is probably due toselection bias whereby those patients receiving other chemotherapyregimens probably had a more favorable prognostic profile since theassociation disappeared when controlling for the other predictivevariables. Previous studies have reported that the duration of PFS is an

important predictor of response to subsequent therapy in recurrentEOC [11,15,16]. Similarly in our analysis, increasing PFS correlated witha longer median survival following recurrence (22 months for thosepatients with PFS≤6months vs. 31months for patients with an initialPFS N24 months), however, the association did not hold when onmultivariate analysis despite seemingly increasing odds of death. Thelimitations of our study include its retrospective nature making itsubject to selection and ascertainment bias. We were also limited bythe incomplete information about salvage chemotherapies for thosepatients with recurrent disease. The strength of our study is the size ofour patient population that was overwhelmingly treated withcontemporaneous platinum and taxane combination chemotherapyand followed for a median of almost 5 years. The results of our studyunderscore the importance of surgical aggressiveness in achievingimproved EOC patient outcomes in the primary as well as therecurrent setting.

The bulk of the literature regarding EDR assays has focused oncorrelation studies that attempted to draw a parallel between resultsfrom predictive in vitro assays and observed outcomes of chemother-apy. However, in these studies, many of the patients do not receiveassay-guided chemotherapy regimens and their results are sometimescontradictory [9]. The original series reported by Kern andWeisenthalhas been criticized for its retrospective nature and its evaluation ofpatients with different types of malignancies whose response tochemotherapy differs from tumor to tumor. Among the small numberof patients with EOC that were included, the response rate of 30% wasmuch lower than what has been reported in most studies as mostpatients received single agent chemotherapy and the population wasnot clearly stratified into those patients receiving salvage therapy andthose receiving primary treatment [7].

Our results are similar to the results reported by Eltabbakh et al. intwo separate reports where the authors reviewed the outcomes of 75patients with EOC and 20 patients with primary peritoneal carcinomawho had specimens sent for EDR assays at primary surgery. Theresponse rates and outcomes were unrelated to EDR to the individualdrugs used in the combination chemotherapy [17,18].

Table 6Summary of studies evaluating chemotherapy sensitivity and resistance assays in patients with EOC.

Study Assay Design Patients Number of Patients Main Findings

Maenpaa [35] Sub renal capsule assay Prospective randomized trial Primary ovarian cancer stagesII–IV

Assay: 63 No difference in OS or overall responseEmpiric: 69

Kurbacher [36] ATP chemosensitivity Prospective non-randomized trial Recurrent ovarian cancer Assay: 25 Statistically significant difference in PFS butnot OS favoring assay-guided therapy.aEmpiric: 30

Loizzi et al. [19] EDR Prospective non-randomized Recurrent ovarian cancer Assay: 50 Statistically significant difference in overallresponse, PFS and OS for patients withplatinum-sensitive disease favoringassay-directed therapy but not for patientswith platinum resistant disease.b

Empiric: 50

Cree [37] ATP chemosensitivity Prospective randomized trial Recurrent platinum resistantrecurrent ovarian cancer

Assay: 94 No statistical difference in overall responserate, PFS and OS.Empiric: 84

Current EDR Retrospective Primary ovarian cancer Assay: 217 No difference in PFS or OS between the 2groups when controlling for age, diseasestage, grade, residual disease and adjuvantchemotherapy.

Empiric: 125

Current EDR Retrospective Recurrent ovarian cancer Assay: 160 No difference in OS between the 2 groupswhen controlling for residual disease andinitial PFS.

Empiric: 96

a More patients in the assay-guided arm received combination chemotherapy. Almost half of the patients in the assay group received a taxane compared to no patients in theempiric group. Not controlled for some important prognostic indicators such as the amount of residual disease. Some patients in the assay-directed group were added to the controlgroup when clinicians preferred a different regimen or when the assay was unsuccessful.

b The study did not control for volume of residual disease after secondary cytoreductive surgery. Groups received similar single agent and combination chemotherapy regimens.Study was not designed to look at subset of platinum sensitive patients.

251A.K. Karam et al. / Gynecologic Oncology 114 (2009) 246–252

The single study of an EDR assay that was designed to compareresponse rates to chemotherapy for recurrent ovarian cancer among100 patients receiving either assay-guided therapy or empiric treat-ment did not impact treatment recommendations despite differencesin survival for those patients with platinum-sensitive disease. Thestudy suffered from a lack of randomized design, a small sample sizeand the nearly identical chemotherapy regimens selected under assay-guidance or empiric therapy [19]. This dramatic difference in survivalcould not be clearly attributed to more effective treatment since thechemotherapy regimens selected under assay-guidance were nearlyidentical to those selected by empiric treatment. In addition theauthors were unable to control for the amount of residual disease afterthe secondary cytoreductive operations, one of the main prognosticfactors affecting the outcome of patientswith recurrent ovarian cancer[20–22] and one of the variables that remained significantly associatedwith survival on multivariate analysis in our study. The authors alsomention that the decision to perform the EDR assaywas determinedbythe volume of disease found during surgery as well as the surgeon'spreference, making it hard to exclude selection bias and confoundingas influences on the results of the study. Table 6 presents a summary ofstudies evaluating the clinical utility of chemotherapy sensitivity andresistance assays in patients with EOC.

In theory the use of chemotherapy sensitivity or resistance assayscould lead to more rational treatment decisions. This approach hashowever a number of limitations. First, in vitro assays cannotreproduce factors that exist in the patient and influence chemo-responsiveness such as variations in tumor vascularity, tumor growthfractions, immunologic factors, and drug metabolism [23]. Moreover,the identification of chemoresistance to one drug among a panel ofdrug does not imply that the remaining drugs will be more effectiveand in vitro EDR does not preclude the possibility that clinicaloutcomes may be different than what is predicted [17,18,24]. In manyinstances no agents show any activity against an individual patient'stumor. Investigators make the assumption that a single specimensampled is representative of both the primary and metastatic disease.Treatment failures occur due to many factors including acquired orinherent resistance or the heterogeneity of tumor in multiple sites[25]. Observations of mixed responses are common among individualpatients with tumors present at multiple sites [26]. It is also not clear ifEDR assays built on tissue obtained early in the tumor's historycorrespond to results that might be obtained downstream withrelapse and sequential treatments. Finally, the chemotherapy combi-

nation that looks most promising on the basis of the EDR assay is oftenthe very same one that would have been chosen in the absence ofassay results [19,27–29]. If the assay rarely alters the recommendedtreatment strategy, the impact of assay results on clinical decisionmaking can only be minor.

These data further support the American Society of ClinicalOncology's conclusion that available evidence is insufficient torecommend routine use of these assays [6,9]. The Working Groupdid emphasize that the rationale for these assays remains strongbecause the number of available chemotherapeutic agents hasincreased enormously over the past few years. Gene-expressionprofiles have emerged as a promising prognostic tool in patientswith EOC [30–32]. These multigene signatures may eventually helppredict clinical outcome and response to chemotherapy in EOC, asthey have for breast cancer and large B-cell lymphoma [33,34].

In conclusion, it would appear that EDR assays and their results donot independently predict or alter the outcomes of patients with EOCwho are treated with the current standard therapy of primarycytoreductive surgery followed by platinum and taxane combinationchemotherapy. Increasing age and residual tumor size continue to beimportant predictors of TTP, OS and RS, especially when all macroscopicdisease is removed. Although our results do not support the routine useof EDR assays to guide therapy for EOC in the primary or recurrentsetting, they do further highlight the importance of cytoreductivesurgery and amount of residual disease. The growing number ofpromising chemotherapeutic and targeted biologic agents, for thetreatment of EOC, justifies the continued investigation of traditional invitro sensitivity and resistance assays along side gene microarrays andother emerging bioinformatics technologies for selecting individualizedtreatments based on features of tumor biology.

Conflict of interest statementThe authors declare that there are no conflicts of interest.

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