An evaluation of survival of ovarian cancer patients with clear cell carcinoma versus serous carcinoma treated with platinum therapy: A Gynecologic Oncology Group experience.

5534 Background: We examined disparities in prognosis between patients with ovarian clear cell carcinoma (OCCC) and serous epithelial ovarian cancer (SOC). Methods: Data from stage I-IV epithelial ovarian cancer (EOC) patients who participated in 12 randomized GOG protocols using platinum-based chemotherapy were reviewed. Proportional hazards models adjusted for age and stratified by protocol, treatment arm, stage, performance status (PS), and race were used to compare progression-free survival (PFS) and overall survival (OS) by cell type (clear cell versus serous). Results: There were 10,803 patients enrolled, 1272 were not eligible: leaving 9,531, of whom 544 (6%) had OCCC, 7,054 (74%) had SOC, and 1,933 (20%) had other; only the OCCC and SOC are considered here. OCCC were significantly younger, more often of Asian race, stage I, good PS, and optimally surgically debulked than SOC patients. Prior to adjustment, OCCC had better PFS and OS due to better prognostic factors. There was no significant difference in PFS or OS for early stage OCCC patients compared to high-grade (HG) SOC patients. For late stage patients, OCCC had poorer PFS and OS compared to SOC, OS HR= 1.66 (1.43, 1.91; p < 0.001). For both optimal, HR = 1.34 (1.10, 1.63; p = 0.003) and suboptimal, HR = 3.18 (2.13, 4.75; p < 0.001) OCCC had a significantly poorer OS than SOC. After adjusting for age and stratified by protocol and treatment arm, stage, performance status, and race, OCCC had a significantly decreased OS, HR= 1.53 (1.33,1.76; p < 0.001). In early stage cases, there was a significantly decreased treatment effect on PFS for consolidative therapy with weekly taxol versus observation in SOC compared to OCCC (p = 0.048). Conclusions: This is one of the largest analyses to date of OCCC treated in a uniform manner . OCCC patients have better PFS and OS compared to SOC; this, is due to their better prognostic factors. There was no observed difference in PFS or OS for early stage OCCC versus HGSOC. In late-stage patients, OCCC was significantly associated with decreased OS which was true for both optimal and suboptimally debulked patients. Finally, treatment effect was influenced by histology.