e13034 Background: Patients successfully treated for hormone receptor (HR)-positive early breast cancer remain at risk of recurrence and metastatic disease even after extended periods of disease-free years. Whether prolonged metastatic-free intervals ultimately confer a benefit to breast cancer-specific survival is not well understood. This study aimed to investigate metastatic-free intervals and risk of breast cancer-specific mortality among patients with HR-positive breast cancer after adjuvant therapy. Methods: We conducted a retrospective cohort study of women aged 18 years and older diagnosed with recurrent metastatic HR-positive breast cancer between 1990 and 2016 in the Surveillance, Epidemiology, and End Results registries. Patients with longitudinal information on primary stage I-III HR-positive breast cancer through the occurrence of metastatic disease and survival were included. Risks of breast cancer-specific mortality associated with metastatic-free intervals (defined as time from primary breast cancer diagnosis to metastasis) of ≥5 years compared to < 5 years were estimated. Fine and Gray competing risks regression models were used to calculate subdistribution hazard ratios (SHR) and 95% confidence intervals (CI). Results: Among 1,057 women with HR-positive breast cancer with a median age of 54 years at primary breast cancer diagnosis and 62 years at metastatic progression, 65% of women had a metastatic-free disease interval ≥5 years, whereas 35% had an interval of < 5 years. Overall, patients with metastatic-free intervals < 5 years had a five-year breast cancer-specific survival rate of 31% compared to 52% in women with intervals of ≥5 years. In multivariable analyses adjusted for age, race, diagnosis year, grade, treatment and sites of metastasis, patients with intervals of ≥5 years had decreased risk of breast cancer-specific mortality (SHR = 0.72, 95% CI 0.58-0.89, P = 0.002) compared to women with metastatic-free intervals of < 5 years. Conclusions: In this population-based study, rates of cancer-specific mortality among patients who experienced metastatic recurrence of HR-positive breast cancer were lower in women with metastatic-free intervals of 5 years or more. The results of this study may inform patient-clinician discussions surrounding prognosis and treatment selection among HR-positive patients.
Increased risk of breast cancer-specific mortality among women with second primary breast cancer: A SEER population-based study
