Endocrine Maintenance Therapy in High-Grade Serous Ovarian Cancer: A Retrospective Off-Label Real World Cohort Study

Background Endocrine therapy is standard of care of maintenance treatment for estrogen receptor (ER) positive breast cancers and is increasingly used in low-grade serous ovarian cancer. However, its therapeutic role in the early maintenance setting for ER positive high-grade serous ovarian cancer (HGSC) remains undefined. Methods A retrospective analysis was conducted on clinicopathological data from patients with newly diagnosed ER positive HGSC following completion of adjuvant chemotherapy. Patients received maintenance therapy either with or without aromatase inhibitor letrozole, in addition to standard maintenance care. ER expression levels and the administration of letrozole were analyzed, along with outcome measures for the entire cohort, with stratification based on residual disease status. Results A total of 102 patients with newly diagnosed HGSC were included in the analysis, with 64 (62.7%) receiving letrozole and 38 (37.3%) not receiving letrozole. The median ER expression was 70%, with higher expression observed in the letrozole group compared to the no letrozole group (77.5% vs. 60%). No significant correlation was found between ER expression status and therapy response (P=0.295 and P=0.176, respectively). Letrozole therapy was well tolerated with no major adverse effects reported. In the overall cohort, maintenance letrozole therapy did not confer a significant improvement in progression-free survival (median 20.56 months vs. 29.34 months, P=0.53) or overall survival (OS) (median 79.48 months vs. 46.85 months, P=0.71) over a median follow-up duration of 23.5 months. However, among patients with no residual disease, maintenance letrozole therapy was associated with statistically significant improvement in OS compared to those not receiving letrozole (median 114 months vs. 46.9 months, P=0.006). Conclusions Maintenance letrozole therapy appears to be well tolerated and potentially beneficial intervention in a subset of patients with ER positive HGSC with no residual disease post-treatment. These findings highlight the need for further validation through prospective randomized trials to comprehensively assess the efficacy of endocrine therapy in this setting and its implications for patient quality of life.