Predicting response to neoadjuvant chemotherapy (NAC) in epithelial ovarian carcinoma (EOC).

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e15555 Background: NAC is increasingly used in the management of EOC and is not inferior to primary surgical debulking. Methods to assess response to NAC remain poorly defined. Predictive markers would ideally allow selection of patients more likely to have a favourable outcome with NAC. This retrospective study analyses clinical, laboratory and radiologic characteristics, in order to identify predictive markers of response to NAC. Methods: Eligibility: patients with Stage III/IV EOC, received ≥3 cycles NAC, underwent primary delayed surgery. Variables included performance status, serum albumin, baseline Ca125 level and %change in Ca125 during chemotherapy, CT radiologic findings. Outcome defined as optimal debulking and pathologic response (PR). Statistical analysis performed using SPSS17. Results: 62 patients, mean age 59.5 years (30-82). Patient characteristics shown in the table. Mean albumin 38 (13-53), mean baseline CA-125 2668 (64-14549). 74% had decline in Ca125 after one cycle, mean decrease 45% (1-91%). 11% had rise in CA-125after cycle 1. Mean %decline in CA-125 after 3 cycles 85% (4-100%). Multivariate analysis: no significant association between ECOG or albumin and outcome. The %change in CA-125 between baseline and after 1 cycle was significantly associated with surgical outcome (p =0.028), as was %change in CA-125 between baseline and 3 cycles (p=0.002). Analysis of radiologic variables awaited. Conclusions: Majority of patients achieved optimal debulking after NAC but have macroscopic residual disease on histology. PR is uncommon. The most significant factor identified is the percentage decrease in CA-125. Further prospective research required to identify predictive markers, with particular focus on new imaging techniques (MRI/PET) and biomarkers. Patient characteristics (n=62). ECOG 0 1 2 3 18% 43.5% 14.5% 3% Stage II IIIc IV 3% 61% 37% Histology Serous Endometrioid Clear cell Carcinosarcoma 85.5% 3% 1.6% 5% Chemo Carboplatin-paclitaxel Carboplatin Other 82% 16% 1.6% No. of cycles pre-op ≤4 >4 (5-8) 58% 40% Surgical outcome Optimal debulked ≤1cm Suboptimal debulking >1cm residual Unresectable 76% 10% 8% Histologic outcome pCR Microscopic residual Macroscopic residual Unresectable 6% 18% 68% 8%