Oncologic safety of preoperative controlled ovarian stimulation for fertility preservation among women with ER-positive breast cancer

The oncologic safety of preoperative controlled ovarian stimulation (COS) for fertility preservation in women with an in situ ER-positive (ER+) breast cancer is unclear. A retrospective study at MD Anderson Cancer Center (Houston, TX) compared oncologic outcomes of women with ER+ breast cancer undergoing preoperative COS versus postoperative COS or matched controls not undergoing COS. Among 51 women with ER+ breast cancer undergoing COS from 2014 to 2024, the median follow-up was 5.5 years. 5-year progression-free survival (PFS, primary outcome) rate was similar for preoperative COS (n=32; 94.1%) versus postoperative COS (n=19; 93.3%; p=0.73). Patients undergoing neoadjuvant systemic therapy (NST) and preoperative COS (n=30) experienced a significantly longer time from diagnosis to NST initiation than propensity-score matches who did not undergo COS (48 versus 29.5 days; p<0.0001), but disease-free survival was similar (p=0.15). The authors conclude that among women with ER+ breast cancers, preoperative COS was not associated with increased risk of progression or death.