Breast cancer mortality as a function of age

Abstract

Background: Incidence of breast cancer (BC) in US women continues to increase with age as the strongest risk factor. We aimed to compare clinical, pathological and sociological variables associated to BC diagnosis, as wellas the relative mortality rates of BC patients compared to the general US population.Methods: We performed a retrospective, single-institution study evaluating 52,509 patients diagnosed withunilateral BC at the University of Pittsburgh Medical Center (UPMC) between 1990–2020. Primary outcome wasdeath from any cause with cancer recurrence as a secondary outcome, evaluated for 4 age groups: 20–44, 45–55, 56–69, and 70–90. A dataset of expected mortality for women in the general population over a 10-yearperiod was constructed using the Surveillance, Epidemiology, and End Results (SEER) Program. Observed vs.expected mortality and standardized mortality ratios (SMR) for each age group were calculated.Results: Youngest patients with BC demonstrated the highest SMR at 10-year follow-up from time of diagnosiscompared to the general US population (SMR 9.68, 95% CI: 8.99to 10.42), and remained highest compared toother age groups when analysis was limited to Stage 0/1 disease (10-year SMR 3.11, 95% CI: 2.54 to 3.76). SMRsdecreased with increasing age at diagnosis with an SMR <1.0 in patients diagnosed with stage 0/1 at ages 70–90at 5-year follow-up.Conclusions: Younger BC patients have the highest SMR which declines gradually with age. In the elderly, lowerstage 0/1 SMR’s are found compared to the general population, suggesting the possibility of an associatedprotective effect.