ER-positive breast cancer in younger women shows rising incidence and distinct biology

Younger premenopausal women with ER-positive early-stage breast cancer have rising incidence and face higher risks of recurrence and breast cancer–related death than older women; genomic differences and treatment-related factors such as ovarian suppression use and adherence to endocrine therapy are implicated.

Younger women are experiencing increasing rates of ER-positive early-stage breast cancer. Research finds these patients often have higher risks of recurrence and breast cancer–related death than older women, despite more intensive therapies in some cases. Investigators point to both biological differences and treatment-related factors as possible contributors. Studies are exploring genomic, immune and hereditary patterns that are more common in younger patients. Key points: - SEER data from 2000–2019 show rising incidence of hormone receptor–positive tumours in women aged 20–29 and 30–39 years in the United States. - Premenopausal women with ER-positive early-stage disease have higher recurrence and breast cancer–related mortality than older patients, with the disparity most marked in low-grade, luminal A–like tumours. - Genomic analyses report enrichment in younger women of features linked to poorer prognosis, including homologous recombination deficiency, specific PIK3CA alterations combined with copy number amplifications, and overall higher rates of copy number amplifications. - Treatment-related observations include less frequent use of ovarian function suppression in some settings, lower adherence to endocrine therapy among younger women (with adherence associated with better 5-year disease-free survival in one cohort), and increasing uptake of germline genetic testing per guideline recommendations. Summary: Younger premenopausal women with ER-positive early-stage breast cancer show higher risks and distinct molecular and immune features that are under active investigation for their prognostic and therapeutic implications. Undetermined at this time.