Oliver KE, et al. – This study was designed to examine disparities in prognosis between patients with ovarian clear cell carcinoma (OCCC) and serous epithelial ovarian cancer (SOC). In this largest analyses to date of OCCC treated on multiple cooperative group trials, OCCC histology was more common than SOC in early stage disease. In early stage patients, when adjusted for prognostic factors, PFS was better for OCCC than for SOC. However, in late–stage patients, OCCC was significantly associated with decreased OS. Histology was shown to impact treatment effect.

Methods

• Data from FIGO stage I–IV epithelial ovarian cancer patients who participated in 12 prospective randomized GOG protocols, were studied.
• Progression-free survival (PFS) and overall survival (OS) by cell type (clear cell versus serous) were compared by using proportional hazards models.

Results

• This study incorporated 10,803 patients.
• Among those, 9531 were eligible, evaluable and treated with platinum.
• In addition, 544 (6%) had OCCC, 7054 (74%) had SOC, and 1933 (20%) had other histologies and were not included further.
• PFS was significantly better in OCCC than in SOC patients, in early stage (I–II) patients.
• OCCC had worse PFS and OS compared to SOC, OS HR = 1.66 (1.43, 1.91; p < 0.001), for late stage (III, IV) patients.
• Data demonstrated a significantly decreased OS, HR = 1.53 (1.33, 1.76; p < 0.001) in stage, performance status, and race, OCCC, after adjusting for age and stratifying by protocol and treatment arm.
• Results revealed a significantly decreased treatment effect on PFS for consolidative therapy with weekly Paclitaxel versus observation in OCCC compared to SOC (p = 0.048), in early stage cases.