Operability and chemotherapy responsiveness in advanced low-grade serous ovarian cancer. An analysis of the AGO Study Group metadatabase.

Objective: Since almost two decades standard 1st-line chemotherapy for advanced ovarian cancer (AOC) has been a platinum/taxane combination. More recently, this general strategy has been challenged because different types of AOC may not benefit homogenously. Low-grade serous ovarian cancer (LGSOC) is one of the candidates in whom efficacy of standard chemotherapy should be revised.

Methods: This study is an exploratory case control study of the AGO-metadatabase of 4 randomized phase III trials with first-line platinum combination chemotherapy without any targeted therapy. Patients with advanced FIGO IIIBIV low-grade serous ovarian cancer were included and compared with control cases having high-grade serous AOC.

Results: Out of 5114 patients in this AGO database 145 (2.8%) had LGSOC and of those thirty-nine (24.1%) had suboptimal debulking with post-operative residual tumor >1cm, thus being eligible for response evaluation. An objective response was observed in only 10 patients and this 23.1% response rate (RR) was significantly lower compared to 90.1% RR in the control cohort of high-grade serous ovarian cancer (HGSOC) (p<0.001). Both, LGSOC and HGSOC patients who underwent complete cytoreduction had significantly better progression free survival (PFS) and overall survival (OS) in comparison to those with residuals after primary surgery, accordingly (p<0.001).

Conclusions: Our observation indicates that low-grade serous cancer is not as responsive to platinum-taxane-based chemotherapy as high-grade serous AOC. In contrast, surgical debulking showed a similar impact on outcome in both types of AOC thus indicating different roles for both standard treatment modalities. Systemic treatment of low grade serous AOC urgently warrants further investigations.