Practice patterns related to ovarian function suppression in the SWOG S2010 clinical trial of young women with breast cancer.

522 Background: Addition of ovarian function suppression (OFS) to adjuvant endocrine therapy (ET) improves disease free survival for young patients at high risk of breast cancer recurrence. SWOG S2010, an ongoing clinical trial that has completed enrollment, is examining the benefit of active symptom monitoring for improving 18-month persistence with ET plus OFS. Because data are currently limited on the use of OFS and endocrine therapy in routine practice, this report of S2010 enrollees describes practice patterns related to the prescription of ET for young patients starting OFS plus ET for treatment of stage 1-3 hormone receptor-positive breast cancer. Methods: We characterized the baseline demographic, clinical, and pathologic data from the pre- and perimenopausal patients starting OFS plus ET for treatment of breast cancer enrolled in S2010 using descriptive statistics. Results: Of the 557 participants enrolled on S2010, median age was 44.5 years (range 23.5-57.1), 25% were Hispanic, 6% Black, 6% Asian, and 76% White. In addition, 39% were not college graduates, 9% were uninsured, and 58% worked full time. Most patients were overweight (34%) or obese (39%). Planned ET was aromatase inhibitor (AI) therapy for 423 (76%) and tamoxifen for 134 (26%). For OFS, 425 (80%) received GnRHa injections, 33 (6%) underwent bilateral salpingo-oophorectomy, and 74 (14%) had chemotherapy-induced ovarian failure (CIOF). Of the 32 (43%) participants with CIOF who were under the age of 45, 12 (38%) were planning to receive AI therapy without concomitant GnRHa therapy. There were 294 participants (55%) with anatomic stage 1 ER-positive breast cancer, of whom 127 (43%) did not receive chemotherapy. Of the 174 participants (33%) with anatomic stage 2 disease, 32 (18%) did not receive chemotherapy. Conclusions: Most participants on this clinical trial received GnRHa therapy as their method for OFS, and an AI for their endocrine therapy. We found that a small number of patients under the age of 45 with CIOF did not receive GnRHa therapy and planned to start AI therapy, even though such patients are at high risk of recovery of ovarian function. Additionally, approximately one-quarter of trial participants appeared to have low risk disease based on non-receipt of chemotherapy and anatomic Stage 1, despite NCCN guidance recommending that OFS be reserved for patients with higher risk features. These findings suggest that additional education about the optimal use of OFS in young women with hormone receptor-positive breast cancer may be warranted. Clinical trial information: NCT05568472 .