Objectives To compare clinical outcomes for stage IIIC and IV ovarian cancer patients receiving neoadjuvant chemotherapy and interval cytoreductive surgery followed by up to three versus more cycles of post-operative chemotherapy.

Methods We conducted a multi-institution retrospective cohort study of patients treated from January 2005 to February 2016 with neoadjuvant platinum-based therapy followed by interval surgery and post-operative chemotherapy. The following were exclusion criteria: more than four cycles of neoadjuvant chemotherapy, bevacizumab with neoadjuvant chemotherapy, non-platinum therapy, prior chemotherapy, and elevated CA125 values after three post-operative chemotherapy cycles. Progression-free and overall survival and toxicity profiles were compared between groups receiving up to three cycles versus more that three cycles post-operatively.

Results A total of 100 patients met inclusion criteria: 41 received up to three cycles and 59 received more than three cycles. The groups were similar in terms of age, body mass index, performance status, tumor histology, optimal cytoreduction rates, and median number of neoadjuvant chemotherapy cycles. Median progression-free survival was 14 vs 16.6 months in those receiving up to three cycles versus more than three cycles, respectively (HR 0.99, 95% CI 0.58 to 1.68, p=0.97). Similarly, median overall survival was not different at 47.1 vs 69.4 months, respectively (HR 1.96, 95% CI 0.87 to 4.42, p=0.10). There were no differences in grade 2 or higher chemotherapy-related toxicities.

Conclusions Extending post-operative chemotherapy beyond three cycles in patients receiving neoadjuvant chemotherapy and interval cytoreductive surgery with normalization of CA125 levels was not associated with improved survival or greater toxicity. Future study in a larger cohort is warranted to define optimal length of cytotoxic treatment.