Controlled Ovarian Stimulation After Fertility-Sparing Surgery for Borderline Ovarian Tumors: An Exploratory Cohort Study on Recurrence and Reproductive Outcomes

Borderline ovarian tumors often affect women of reproductive age for whom fertility preservation may be a major concern. While fertility-sparing surgery is widely accepted, the safety of controlled ovarian stimulation for oocyte cryopreservation after surgery remains uncertain due to potential recurrence risk. This retrospective single-center cohort study explored the association between controlled ovarian stimulation following fertility-sparing surgery and both recurrence risk and reproductive outcomes. Patients treated between January 2011 and June 2024 were included. Baseline characteristics, surgical details, and reproductive outcomes were compared using non-parametric and exact tests. Progression-free survival was assessed with Kaplan–Meier estimates and Cox proportional hazards models, modeling stimulation as a time-dependent covariate, and using a 10-month landmark analysis to account for immortal time bias. Of 45 included patients, 19 underwent ovarian stimulation after surgery, with a median interval of 9.9 months to stimulation. Median follow-up was 34.4 months. Recurrence occurred in 21.1% of stimulated patients versus 38.5% of non-stimulated patients (p = 0.338). After adjustment for time-dependent exposure, ovarian stimulation was not associated with increased recurrence risk (HR 0.95, 95% CI 0.22–4.09; p = 0.944). Eleven patients (24.4%) achieved at least one pregnancy, 81.8% of which were spontaneous. Controlled ovarian stimulation for oocyte cryopreservation after fertility-sparing surgery for borderline ovarian tumors did not show an increased recurrence risk, although larger studies are needed.