A prior clinical trial on early-stage high risk ovarian cancer showed a lower recurrence rate in those treated with six vs. three cycles of chemotherapy. We proposed to identify subsets of patients who may benefit from more cycles of chemotherapy.

Outcomes of patients who underwent six vs. three cycles of chemotherapy were analyzed based on clinico-pathologic factors. Kaplan-Meier estimates and Cox Regression Model were used for analyses.

Of 427 patients (median age: 55 years), 69% had stage I disease, 30% had clear cell, 25% endometrioid, 23% serous, 7% mucinous, and 15% had other cell types. The risk of recurrence in those who had six vs. three cycles of chemotherapy was not different based on age, performance status, stage, grade of disease, presence of ascites, tumor rupture, or positive cytology. However, those with serous tumors had a significantly lower risk of recurrence after six vs. three cycles of chemotherapy (HR=0.33, CI=0.14-0.77; p=0.04) in contrast to non-serous tumors (HR=0.94, CI=0.60-1.49). Nevertheless, a test of homogeneity did not show a difference in treatment effects across cell types (p=0.285). Of those with serous tumors, the 5-year recurrence-free survival was 83% and 60% in those who received six vs. three cycles of chemotherapy, respectively (p=0.007).

In this exploratory analysis of early-stage high risk ovarian cancer, our data suggest that six rather than three cycles of chemotherapy may decrease the recurrence of patients with serous tumors. Further studies are needed to confirm these findings.