Ovarian stimulation for oocyte vitrification does not modify disease-free survival and overall survival rates in patients with early breast cancer

Research question: Does ovarian stimulation for oocyte vitrification affect disease-free survival and overall survival rates in women with early breast cancer? Design: This cohort study included 259 patients with early breast cancer; 148 patients underwent ovarian stimulation, whereas 111 patients did not. Patients were treated between January 2008 and December 2016. To calculate the disease-free survival time and overall survival rate, the time of definitive surgery was defined as the starting point. The follow-up was conducted up to 5 years. Results: Exposed and non-exposed groups were comparable in tumour, node and metastases classification, Nottingham grade, hormonal receptor status, tumour molecular phenotype, histology and pathology stage. The exposed group was younger than the non-exposed. Recurrences occurred in 9/148 women (6.1%) in the exposed group and 15/111 women (13.5%) in the non-exposed group, with no significant difference. The mean disease-free survival time was 63.9 months (95% confidence interval [CI]: 61.5-66.4) in the exposed group and 60.6 months (95% CI: 56.9-64.2) in the non-exposed, with no significant difference (log-rank [Mantel-Cox] test). Overall survival rates were comparable; 2/148 (1.4%) and 4/111 (3.6%) patients died, in exposed and non-exposed groups, respectively, during the period analysed. Mean overall survival times were 67.2 months (95% CI: 66.2-68.2) in the exposed group and 65.9 months (95% CI: 64.0-67.9) in the unexposed, with no significant difference (log-rank [Mantel-Cox] test). Conclusions: This study suggests that ovarian stimulation in patients with early-stage breast cancer is safe in the long term.