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Breast Cancer Research and Treatment 66: 225–237, 2001.
2001 Kluwer Academic Publishers. Printed in the Netherlands.
Breast cancer survival and in vitro tumor response in the extreme drug
resistance assay
Rita S. Mehta1,4, Richard Bornstein2, Ing-Ru Yu1, Ricardo J. Parker1, Christine E. McLaren3,4,Khanh P. Nguyen4, Kuo-Tung Li4, and John P. Fruehauf1,41Oncotech, Inc., CA; 2Center for Breast Health, OH; 3Epidemiology Division, Department of Medicine, Universityof California, Irvine; 4Chao Family Comprehensive Cancer Research Center, University of California, Irvine,Orange, CA, USA Key words: breast cancer, chemotherapy, drug resistance, in vitro assay, survival Purpose. To determine whether in vitro extreme drug resistance (EDR) assay results for patients with breastcarcinoma were associated with clinical outcome after chemotherapy.
Patients and methods. EDR assays were performed on tumor tissue obtained from 103 newly diagnosed breast cancer cases. EDR scores of 2 for low, 1 for intermediate, or 0 for extreme drug resistance were determined foreach agent tested. In vitro EDR scores for 4-hydroxycyclophosphamide (4HC) and doxorubicin were summed forpatients treated with AC, or for 4HC and 5-FU for patients treated with CMF. Treatment selection was blinded toassay results.
Results. Median time to progression was significantly shorter for patients with extreme or intermediate in vitro resistance (n = 55, 48 months), compared to patients with low in vitro resistance, (n = 41, 100 months, p = 0.022).
Patients demonstrating extreme to intermediate drug resistance also showed poorer survival than the low resistancegroup (49.5 months vs. not reached, median follow-up 48 months, p = 0.011). Summed EDR scores, stage,and number of lymph nodes were significantly associated with survival in univariate and multivariate analysis.
Compared to EDR scores of 4, summed EDR scores of 0–1 and summed EDR scores of 2–3 were associated witha relative risk of death of 3.09 (95%, CI 1.05–9.06, Cox proportional hazards model, p = 0.040) and 2.35 (95%,CI 1.07–5.15, Cox proportional hazards model, p = 0.033), respectively.
Conclusion. Extreme drug resistance testing identified patients with individual patterns of drug resistance prior to therapy. In this cohort of breast cancer patients treated with chemotherapy, summed EDR scores weresignificantly associated with time to tumor progression and overall survival. EDR results may offer a method foroptimizing treatment selection.
Abbreviations: EDR: extreme drug resistance; IDR: intermediate drug resistance; LDR: low drug resistance; CTX:cyclophosphamide; 4HC: 4-hydroxycyclophosphamide; 5-FU: 5-fluorouracil; MTX: methotrexate; AC: doxorubi-cin and cyclophosphamide; CMF: cyclophosphamide, methotrexate and fluorouracil; CI: confidence interval; ER:estrogen receptor Introduction
Coldman hypothesis by targeting the heterogeneousmalignant clones within each patient [1, 2]. This Multiagent chemotherapy is an important compon- strategy led to the development and clinical valida- ent of treatment for invasive breast cancers > 1 cm in tion of various standard combination chemotherapy size. Combination chemotherapy exploits the Goldie– regimens comprised of non-cross-resistant agents. Re- cent clinical trials have demonstrated that treatment doxorubicin and taxane resistant breast cancer patients with combination chemotherapy can significantly pro- long the lives of breast cancer patients. The degree These observations suggest that the ability to of improved clinical outcomes, however, is mod- identify individual patterns of resistance prior to ini- est and comparable among the various standard re- tiating chemotherapy might have a substantial clinical gimens [3, 4]. In a recently reported Inter Group impact. Tailoring treatment regimens by eliminating trial for node negative patients, the marginally super- agents found to be inactive in vitro prior to therapy ior disease free and overall survival with the CAF administration would potentially avoid the toxicity, regimen, compared to the CMF regimen, was bal- lost time, and costs associated with ineffective treat- anced by modestly increased toxicity [5]. For node ment [25–27]. This is especially important in an era positive patients, FAC/CAF, AC followed by paclit- that has witnessed the introduction of a variety of axel, doxorubicin followed by CMF, or CMF alone new, non-cross-resistant classes of agents (taxanes are all considered to be appropriate options [4, 6– [28, 29], gemcitabine [30], and vinorelbine). Treat- 8]. The majority of randomized clinical trials have ment with paclitaxel, vinorelbine, or docetaxel has led failed to demonstrate a benefit from high dose chemo- to similar durations of quality- adjusted progression- therapy with stem cell rescue for high risk patients free survival in anthracycline-resistant breast cancer [31]. With the advent of more agents to choose from, The inability to demonstrate a clear superiority of and third-generation in vitro drug response assays, it one regimen over another, or the superiority of high may be possible to tailor combination therapy to the dose combination regimens over standard dose chemo- unique drug response characteristics of each patient’s therapy, suggests that a plateau in benefit may have tumor [32, 33]. For this potential to be realized, in vitro been reached using the current non-targeted, empirical assays must be evaluated for their ability to predict approach to treatment selection. The empirical use of one of the standard regimens for a specific patient does Although the predictive accuracy of the in vitro ex- not routinely take into account that patient’s unique tu- treme drug resistance (EDR) assay to identify drugs mor biology. On the other hand, treatment targeted to unlikely to demonstrate clinical response with greater the patient’s tumor characteristics holds promise. The than 99% accuracy has been established in a double initial proof of principle that targeted therapy could blind retrospective study [33], there is paucity of data be a useful strategy stemmed from observations that on the relationship between EDR assay results and tamoxifen treatment could significantly improve sur- survival. The present study was, therefore, conducted vival in patients with estrogen receptor (ER) positive in breast cancer patients to examine the relationship tumors [16]. In addition, the benefit of targeted treat- between in vitro EDR assay results, and progression- ment has been demonstrated in two retrospective trials free and overall survival. EDR assay results were where dose escalated doxorubicin-based chemother- obtained for a serial cohort of 103 cases prior to first apy was found to be superior in lymph node-positive line chemotherapy. The treating physician was blinded patients whose tumors overexpressed Her-2/neu [17, to EDR results, and lab personnel were blinded to 18]. More importantly, Herceptin therapy targeted to clinical characteristics. We report here the relationship Her-2/neu overexpressing breast cancer patients has between EDR assay results and patient outcomes after yielded improved survival in a prospective randomized treatment with agents tested in the assay.
trial when given in combination with cisplatin or pacl-itaxel chemotherapy [19]. These observations support Patients and methods
the notion that tailoring treatment to each patient’stumor characteristics can be advantageous. Clinical trials with cross over designs in breast cancer havevalidated the concept of individual patterns of drug- Between October 1990 and March 1996, tissue specific resistance, with some patients failing single samples from 187 serial patients with newly diagnosed agent paclitaxel, yet subsequently responding to non- invasive breast cancer for which tumor tissue could be cross resistant doxorubicin on cross over, or vice versa obtained were sent from a single NSABP institution to [20, 21]. Additionally, docetaxel has demonstrated Oncotech, Inc. (Irvine, CA) for in vitro drug resistance significant responses in doxorubicin resistant patients, testing. We performed a retrospective double-blinded while capecitabine has shown modest responses in study on a serial group of patients who had specimens In vitro drug response and breast cancer survival submitted for EDR assays. Our primary objective was viable malignant cells per well were suspended in soft to determine if in vitro drug response was associ- agarose and growth media in a 24-well plates and ated with clinical outcomes. Treating physicians were exposed to the following chemotherapeutic agents: blinded to EDR results, as were the personnel who doxorubicin, 5-FU, or 4-hydroxycyclophosphamide collected clinical outcome data. EDR assays were (4HC), the active metabolite of cyclophosphamide.
unsuccessful in 17 cases (9%). Thus, EDR results Melphalan was employed as a cyclophosphamide sur- were available for 170 patients (91%). Eleven patients rogate for the first 10 cases because the 4-hydroperoxy were lost to follow-up. Of the remaining 159 cases, formulation of cyclophosphamide was not available 103 cases were treated with primary chemotherapy, for in vitro use when this study was initiated. When of which 96 cases had a complete EDR profile of 4- 4HC became available, a series of cases were run to hydroxycyclophosphamide (4HC) and doxorubicin for compare melphalan with 4HC on the same specimens.
patients treated with AC, or for 4HC and 5-fluorouracil Using spearman’s correlation coefficient, a highly sig- (5-FU) for patients treated with CMF.
nificant association was found between in vitro per- Primary treatment consisted of mastectomy with cent cell inhibition (PCI) produced by 4HC versus axillary lymph node dissection, or lumpectomy with melphalan (R = 0.43, p < 0.0001) (n = 468). Based axillary node dissection and local radiation. A small on this association, we included the in vitro response (0.2–1 g) section of representative malignant tissue data for the 10 cases tested against melphalan as a from the primary tumor or involved lymph node was placed in transport media and sent overnight to On- Drugs were added to wells containing the malig- cotech for analysis in the in vitro EDR assay. Chemo- nant cells at doses that approximated their in vivo therapy was started 14 to 21 days after definitive peak plasma concentrations [32, 33]. Treated cell sus- surgery. The following two regimens were employed: pensions were incubated for 72 h with drug and thenpulsed with 5 µCi 3H-thymidine. After an additional 1. CMF – cyclophosphamide 100 mg/m2 days 1– 48-h incubation period, agarose-cell suspensions were 14, methotrexate 40 mg/m2 and 5-fluorouracil liquefied at 96◦C, well contents were harvested onto 600 mg/m2, day 1 and day 8, every 28 days for glass fiber filters, and cells were lysed with deionized water. The incorporated radioactivity in the filter- 2. AC – cyclophosphamide 600 mg/m2 and doxoru- trapped macromolecular DNA was measured by liquid bicin 60 mg/m2, day 1 every 21 days for 4 cycles.
scintillation as counts per minute (CPM). Positive White blood cell and platelet counts were monitored, control (supralethal cisplatin-exposed) and negative with dosages adjusted prior to each cycle if needed.
control (media-exposed) cultures were performed with EDR assays were performed prior to the initiation each assay. Results were reported as percent cell in- of chemotherapy. Patients were subsequently treated hibition (PCI) compared with media-exposed control with classical CMF or AC regimens independent of cultures after subtraction of positive control CPM. The the assay results. Less than one third of the patients performance characteristics, including the population received hormone therapy, and these cases were bal- median PCI and standard deviation (SD), were de- anced between the two in vitro drug response groups termined for 4HC (n = 372), 5-FU (n > 6,000) and doxorubicin (n > 3,000) on independent cases evalu-ated using the same methods. Individual patient PCI values were compared to the median and SD estab-lished for each agent to determine their EDR score.
Once received at Oncotech, tumor tissue sampleswere accessioned and assigned a tracking number. Tu- mor specimens were mechanically disaggregated intosuspensions of small tumor clumps. Stained tissue For each patient’s tumor specimen, in vitro responses sections and cytospin preparations of tumor suspen- to individual drugs were scored as ‘0’ for extreme sions were reviewed by a pathologist to confirm the drug resistance (EDR) when the PCI was ≥ 1SD below diagnosis and the presence of adequate numbers of the median, ‘1’ for intermediate drug resistance (IDR) malignant cells. Tissue culture was performed as pre- when the PCI was between the median and 1SD be- viously described [32, 33]. Cell viability was determ- low the median, or ‘2’ for low drug resistance (LDR) ined by trypan blue exclusion. Approximately 30,000 when the PCI was above the median. EDR scores for 4HC and doxorubicin were summed for patients istical tests were two-tailed and a significance level of treated with AC. 4HC and 5-FU scores were selected 0.05 was used. All clinical outcomes and laboratory for summation for patients treated with CMF. Me- data were independently reviewed by the Biostatistics thotrexate was not tested in the EDR assay because the addition of thymidine for labeling rescues DNAsynthesis, thereby yielding an inaccurate measure ofproliferation inhibition. Further, methotrexate has only limited activity by itself, but it significantly potentiates5-FU toxicity when both compounds are administered.
Summed EDR Scores ranged from 0 to 4. For ex- At a median duration of follow-up of 48.17 months, ample, a patient treated with AC and having a tumor there were 59 surviving patients out of 96 patients with extreme resistance to 4HC and low resistance to who had successful EDR assay results for at least two doxorubicin was assigned an EDR Score of 0 + 2 = 2.
of the chemotherapy agents they received. Details ofpatient characteristics for the cohort of 96 patients treated with chemotherapy, and for whom a completeEDR profile was available are detailed in Table 1.
We examined the relationship between the frequencies Patients were treated with classical CMF or AC re- of tumors with low resistance scores (4), or extreme gimens. Some patients received additional hormone to intermediate resistance scores (0–3), and patient therapy. Treatment profiles are shown in Table 2.
clinical characteristics using contingency table ana-lysis with the chi-squared test or Fisher’s exact test.
Prognostic indicators considered as categorical vari-ables included age, stage, number of involved lymph- Single agent EDR assay results for the 96 patients nodes, tumor size, and ER receptor status. Similarly, treated with chemotherapy that had summed EDR we examined the association between the dichotom- scores are shown in Table 3. The incidence of ex- ized EDR scores and treatment modalities, including treme drug resistance to the treatment drugs varied: mastectomy versus lumpectomy/radiation, hormonal 13% for 4HC (or the index alkylator, Melphalan), 5% treatment and chemotherapeutic regimen. Time to tu- for doxorubicin, and 19% for 5-FU. The incidence of mor progression and overall survival were calculated intermediate resistance ranged from 25% to 32%, and from the date of diagnosis to date of progression or the incidence of low drug resistance ranged from 49% death, respectively. For overall survival, death from to 62%, respectively, for the individual drugs. The any cause was considered as an event. Data from pa- EDR scores for 4HC and doxorubicin were summed tients without events were censored at the date of last for patients treated with AC (n = 42), and EDR scores follow up. Progression free and overall survival curves for 4HC and 5-FU were summed for patients treated were constructed using the Kaplan–Meier method, and with CMF (n = 54). Table 4 shows the EDR assay differences between groups were assessed by the log- results and the corresponding summed EDR score cat- rank test. Univariate analysis included age, stage, egories for the study set. Fifty-five tumors (57%) ex- degree of lymph node involvement, ER status, surgical hibited extreme or intermediate drug resistance, with treatment with or without radiation, chemotherapy re- summed EDR scores for these cases ranging from 0 to gimens, hormonal treatment status, and single agent 1 and 2 to 3. Of these tumors, only two demonstrated EDR scores, and composite EDR scores. We used the EDR to both drugs (summed EDR score of 0), and Cox Proportional Hazards Model to evaluate the influ- only eight cases showed EDR to one drug in conjunc- ence of prognostic factors on survival in univariate and tion with IDR to the other (summed EDR score of 1).
multivariate models. To assess the relative influence of Forty-one (42%) patients were treated with a two-drug prognostic factors on progression-free and overall sur- combination to which their tumors showed low in vitro vival, we included the variables that were predictive of resistance (summed EDR score of 4). Patients with survival in univariate analyses (EDR scores, stage and summed EDR scores of 0 to 1 and 2 to 3 were grouped lymph nodes) in multivariate models. We also used into the extreme and intermediate resistance categor- the log-rank test for trend to assess the association ies, respectively, while patients with summed EDR of progression-free survival, or overall survival, with scores of 4 were placed into the low drug resistance EDR scores trichotomized as 0–1, 2–3, and 4. All stat- In vitro drug response and breast cancer survival Table 1. Comparison of patient characteristics and summed EDR scores Table 2. Comparison of treatment modalities related to summed EDR scores Table 3. In vitro drug resistance profiles for single agents treated with AC. For the 96 patients with successful assays for two of the drugs they received (42 patients received AC; 54 patients received CMF), their respect-ive summed EDR scores for intermediate and extreme versus low drug resistance (0–3 vs. 4), lymph node status, and stage were significantly associated with progression-free and overall survival in univariate ana-lysis. Figure 1 and Table 5A show the influence of thelevel of drug resistance on time to tumor progression, Table 4. Composite EDR scores profile with a median of 100 months for patients with lowdrug resistance, compared to 48 months for patients with intermediate to extreme-resistance (log-rank test hazard ratio 2.05, CI = 1.110–3.747, p = 0.022). No statistically significant difference was found between the intermediate to extreme resistance and low drug resistance categories with respect to age, lymph node status, stage, size of primary tumor, ER status, primary surgical, radiation, hormonal and chemotherapeutic ∗EDR: extreme drug resistance; IDR: intermediate drug resist- treatment (Tables 1 and 2). However, there was a trend in the intermediate to extreme-resistance groupfor smaller tumor size (p = 0.072), negative lymph-nodes (p = 0.246), and cases undergoing lumpectomy Correlation of outcomes with EDR scores and radiation rather than mastectomy (p = 0.058).
Of the evaluable cases with at least one successful drug A significant difference in survival was noted result in the EDR assay, 103 received primary chemo- between patients with intermediate to extreme drug therapy. At a median follow up time of 48 months, resistance (summed EDR scores of 0–3), compared 37 of the 96 patients with full EDR profiles had died, with the low drug resistance group (summed EDR and 43 patients had progressed. Table 5, panels A score of 4) in univariate analysis using log rank test and B, show the association of EDR results for single (p = 0.010) (Table 5B; Figure 2). Patients with inter- agent 4HC and 5-FU with progression-free (p = 0.056 mediate to extreme-drug resistance demonstrated sig- and p = 0.042) and overall survival (p = 0.078 and nificantly shorter survival, with 5-year survival rates of p = 0.005) for patients receiving a Cytoxan contain- 45% compared to 81% in patients with low drug resist- ing regimen (n = 99) or a 5FU containing regimen ance. Median survival was 50 months in the intermedi- (n = 56), respectively. The association of survival and ate to extreme-resistance group, while the median sur- EDR results for single agent doxorubicin did not reach vival for the low resistance group had not been reached statistical significance (p = 0.286) for the 44 cases Table 5A. Univariate analysis and progression-free survival ∗EDR score was summed for two of the agents received by the patient as described inMaterials and methods.
In vitro drug response and breast cancer survival Table 5B. Univariate analysis and overall survival ∗EDR score was summed for two of the agents received by the patient as described inMaterials and methods.
log-rank test). Age, lymph node status, stage, ER Discussion
status, and hormonal treatment status have all been re-ported to influence survival independent of the chemo- This study demonstrated a significant association therapeutic regimen used. In this cohort, stage and between survival and EDR assay results for primary lymph node status were the only other variables sig- tumor tissues obtained from breast cancer patients nificantly associated with progression-free and overall prior to chemotherapy. The treatment of these pa- survival (Tables 5A and 5B). The relative probab- tients was blinded to assay results. With respect to ility of progression and death was 2.19 (CI 1.24– potential bias between groups, prognostic factors were 4.35, p = 0.022) and 2.49 (CI 1.18–5, p = 0.017) for not found to be significantly different between pa- patients treated with agents showing in vitro inter- tients with intermediate to EDR (score 0–3) and LDR mediate to extreme-resistance compared to patients (EDR scores 4). However, there was a trend in the treated with low drug resistance agents, using Cox intermediate to EDR group for smaller tumor size proportional hazards model (data not shown).
(p = 0.072) and presentation with negative lymph- In view of the significant association between nodes (p = 0.246), compared to patients in the LDR the dichotomous EDR score categories of 0–3 and group. More patients, therefore, underwent lumpec- 4 variable and progression free and overall survival, tomy and radiation in the high resistance group as we evaluated the trichotomous variables of low, in- opposed to higher numbers of patients undergoing termediate, and extreme resistance using summed mastectomy in the low resistance group. This trend EDR scores of 4, 2–3, and 0–1, respectively. As may have potentially biased results against an associ- shown in Figures 2A and 2B, the log-rank test for ation between EDR assay results and survival. Using trend demonstrated a significant association between a Cox Proportional Hazards model adjusting for the these three resistance categories and progression-free variables significant in univariate analysis, the relative (p = 0.013) and overall survival (p = 0.002), respect- risk of death for patients with adverse EDR scores of ively. Table 6A depicts the results of analysis using 0–1 and 2–3 was 3- and 2-fold higher, respectively, the Cox proportional hazards model for progression- compared with patients with a favorable EDR score of free survival for summed EDR scores of 0–1 and 2–3 versus summed EDR scores of 4 (Relative risk 2.60, In vitro patterns of resistance varied among pa- CI 0.94–7.22, p = 0.066 and Relative risk 2.09, CI tients, with few patients showing resistance to all 1.04–4.24, p = 0.039, respectively), adjusted for stage drugs tested, suggesting that alternative agents may and lymph node status. Similarly, Table 6B illustrates have been available to chose from for a majority of Cox proportional hazards model showing that EDR patients when one specific agent was found to be in- scores were independent predictors of survival when active in vitro for a given patient. Further, there was patients with extreme and intermediate drug resistance a significant association between in vitro drug res- were compared with patients with low drug resistance istance for single agent 5-FU and progression-free (Relative risk 3.09, 95%, CI 1.05–9.06, p = 0.040 (p < 0.0423) and overall survival (p < 0.005) of pa- and Relative risk 2.35, 95%, CI 1.07–5.15, p = 0.033, tients treated with CMF, suggesting that the clinical activity of 5-FU in the CMF regimen may be a ma-jor determinant of outcome for patients treated with Figure 1. (a) Kaplan–Meier progression-free survival curves for patients with EDR scores of 4 (—–) vs. < 4 (—-); (b) Kaplan–Meier overallsurvival curves for patients with EDR scores of 4 (—–) vs. < 4 (—-).
CMF. We also noted that single agent 4HC EDR methotrexate acted as a modulator of 5-FU or 4HC scores showed a trend towards a significant associ- cytotoxicity. Absence of in vitro assay results for me- ation with progression-free (p < 0.056) and overall thotrexate did not detract from the robust nature of survival (p < 0.078) for patients treated with AC or in vitro 4HC or 5-FU response association with PF CMF. Because methotrexate cannot be reliably tested and OS. The significant relationship between in vitro in vitro, it was not possible for us to evaluate if drug resistance scores and survival supports the no- In vitro drug response and breast cancer survival Figure 2. (a) Kaplan–Meier progression free survival curves for patients with EDR scores of 4 vs. 2–3 vs. 0–1; (b) Kaplan–Meier overallsurvival curves for patients with EDR scores of 4 vs. 2–3 vs. 0–1.
Table 6A. Progression-free survival: Multivariate analyses of The drug exposures used in the EDR assay are 5– 10 times higher than those achieved in vivo, biasing assay reliability towards accurate detection of drug resistance. In correlating in vitro drug resistance withclinical response, only 1 out of 127 patients showing in vitro EDR showed clinical response, while 52% of patients showing in vitro sensitivity demonstrated clinical response. The prediction of resistance may be more robust than the prediction of sensitivity because of the inability of in vitro systems to parallel relevant in vivo pharmacodynamics, such as individual vari- ations in tumor vascular supply and drug metabolism,that influence clinical response. The practical utilityof in vitro testing has been enhanced by the devel-opment of third generation assay techniques, such as Table 6B. Overall survival: Multivariate analyses of prognostic the EDR assay employed in this study. While older clonogenic systems yielded results in 2–3 weeks with50% success rates, newer technologies have shortened assay time to less than one week and improved the evaluability rate to 85%, which is similar to the eval- uability rate of 91% in the present study [27]. Yet, the relationship between in vitro results and survival has not been adequately addressed either by chemo- sensitivity or chemoresistance assays. Our study is the first large series to demonstrate the clinical relevance of in vitro drug resistance for patients with all stages of breast cancer treated with first line chemotherapy.
We found that patients treated with combinations ofdrugs with low in vitro drug resistance enjoy betterprogression-free and overall survival. Patients whowere treated with combinations of drugs found to be tion that drug resistance testing can identify a tumor intermediate or extremely resistant in the EDR assay phenotype related to clinical outcome. Information re- had a 5-year survival rate of only 45%, compared garding the unique in vitro drug response profile of an to 81% for patients who were treated with a com- individual patient may potentially be exploited to im- bination of drugs to which their tumors showed low prove outcomes by tailoring treatment based on assay The improved survival demonstrated for patients Several smaller studies have indicated that re- treated with combinations of low resistance agents sponse rates are improved when patients received is intriguing. In a recent review, 12 of 17 studies chemotherapy to which their tumors were not res- were found to demonstrate a statistically significant istant in vitro [27, 33–35]. A review of published survival advantage for patients treated with agents in vitro assay results for 4,263 patients, where correla- to which they were ‘sensitive’ in vitro [27]. Three tions with treatment response were available, indicated prospective studies, two of which were randomized, that clinical response rates were significantly associ- showed a survival advantage for patients treated with ated with in vitro results, with an overall sensitivity assay-directed therapy [27]. More recently, a random- of 85%, and an overall specificity of 80% [27]. Of ized study by Cortazar demonstrated that survival was note was the finding that prediction of drug resistance improved for small-cell lung cancer patients random- was > 90% accurate, compared to 72% accuracy for ized to assay directed therapy [36]. Orr et al., have prediction of chemosensitivity. The EDR assay was shown that costs can be lowered using assay direc- reported to have a negative predictive accuracy of 99% ted therapy, with at least equivalent survival in newly in a double-blind retrospective study of 450 cases [33].
diagnosed, optimally resected ovarian cancer patients In vitro drug response and breast cancer survival [25]. Gambino et al., demonstrated high response rates The following authors have a financial interest in with assay directed therapy in patients with chemo- Oncotech, the Principle Sponsor of this study: R.
therapy refractory gynecological malignancies [37].
Mehta, I.Y. Yu, R. Parker, and J.P. Fruehauf.
Similarly, a prospective trial by Kurbacher et al.,demonstrated a high response rate and promising sur-vival outcomes in recurrent ovarian cancer treated withtherapy tailored according to their in vitro assay res- References
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