Early-stage clear cell ovarian cancer compared to high-grade histological subtypes: An outcome exploratory analysis in two oncology centers.

Objective: advanced stage clear cell ovarian cancer (CCOC) carries a higher risk of relapse and death compared to other histological subtypes. The prognosis of early-stage CCOC is controversial.
Methods: Early-stage high-grade OC patients from two Italian oncologic centers were included. Patients with early-stage CCOC were compared with those with high-grade endometrioid (HGE) and serous (HGS) OC in terms of relapse-free interval (RFI), cancer-specific survival (CSS) and post relapse cancer-specific survival (prCSS). The Cox proportional hazard model and the restricted mean survival time were used.
Results: Between 1981 and 2012, 134 patients with CC, 152 with HGE and 160 with HGS were treated at two referral centers. Median follow-up was 11.5 years. Ten years RFI rates were 80.6%, 72.1%, 60.6%, and CSS rates were 84.3%, 82.6%, 81.7% respectively. Adjuvant chemotherapy significantly improved RFI (aHR 0.61, 95%CI 0.40 to 0.91, P = 0.015). In the multivariable analysis HGS histotype was associated with a shorter RFI compared to CC, (Hazard Ratio [HR]: 1.81; 95%CI: 1.12-2.93; P = 0.016), whereas CSS was not statistically different. prCSS was longer in HGS compared to CCOC (HR, 0.36; 95% CI, 0.17-0.74; P = 0.006). According to the stage, IA/IB/IC1 HGSOC had a shorter RFI (HR, 2.13; 95% CI, 1.14-3.99; P = 0.018) compared to IA/IB/IC1 CCOC, but similar CSS. For prCSS, CC compared to HGS conferred a worse prognosis regardless of the initial stage.
Conclusions: Early-stage CCOC is associated with a longer RFI, similar CSS and a shorter prCSS compared to HGSOC. No prognostic differences were observed between CC and HGE OC. The relapse risk was the lowest in IA/IB/IC1 CC compared to HGS, whereas CC displayed poor sensitivity to chemotherapy after relapse.
Competing Interests: Declaration of Competing Interest Dr. Colombo reports personal fees from Roche, Pharmamar, Astra Zeneca, Clovis, Tesaro, GSK, Pfizer, Amgen, Immunogen, MSD, Advaxis, Takeda, Novartis, Elipses and Biocad, outside the submitted work. The authors report no other conflicts of interest in this work.
(Copyright © 2020 Elsevier Inc. All rights reserved.)