As the population ages, more patients will be diagnosed with BC. Currently, about 50% of newly diagnosed BC patients are aged >65 years, with about 25% of this older population being aged >80 years (or about 11% of the total BC population). Due to decreases in physiologic reserve, age-related pharmacokinetic and pharmacodynamic changes, altered organ function, comorbidities, and polypharmacy in older adults, the treatment of BC is more complicated in this group.
To help discern the clinical and pathological characteristics, treatments, and long-term outcomes of patients with hormone receptor positive/human epidermal growth factor 2 negative (HR+/HER2-) BC in those aged 65 to 79 years and in those aged >80 years, data from the National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results (SEER) database were analyzed to determine the effect that adjuvant chemotherapy (ACT) has on overall survival (OS) and cancer-specific survival (CSS) in both cohorts of older adults. NCI’s SEER program collects and publishes data on cancer incidence and survival from population-based cancer registries in 22 U.S. geographic areas.
This retrospective, propensity-matched cohort study analyzed data from the SEER 17 registry. This study enrolled female patients diagnosed with HR+/HER2- primary invasive ductal BC between 2010 and 2015 who had undergone surgery and received postoperative system adjunctive therapy. Patients were excluded if they were male, if they were diagnosed before age 65 years, if patients were in stage T0, Tx, or Nx, if patients had distant metastases (M1 stage), and if data were missing. The primary study endpoints were OS, which was calculated as the date of diagnosis to the date of death from any cause, and CSS, which was defined as the date of diagnosis to the date of direct or indirect death from BC.
There were 38,128 patients enrolled in the 65- to 79-years age group and 7,634 patients in the 80+ years age group. Statistically significant differences between the groups included that those in the 80+ group had a higher tumor histological grade and later T and N stages. The octogenarian group were less often married and were less likely to receive either radiation therapy (63.2% vs. 40.3%, P <.05) and chemotherapy (20.7% vs. 3.76%, P <.05) compared with their younger counterparts.
Survival was assessed prior to and after propensity-score matching for those who received ACT. There were 5,543 BC patients in the ACT and non-ACT groups in the matched patient cohorts aged 65 to 74 years and 232 patients aged 80+ years in the ACT and non-ACT groups. Post propensity matching, ACT was found to be effective in improving OS (P <.001) but not in enhancing CSS (P = .092) for those aged 65 to 74 years. The effect on OS was evident in subgroup survival analyses based on all histologic grade subgroups and advanced T and N stages. ACT improved CSS in T3, T4, N2, and N3. Unfortunately, for those aged 80+ years, ACT treatment had no effect on OS (P = .79) or on CSS (P = .091).
The findings of this paper have important ramifications for pharmacists who care for older adults with BC since their role is optimizing drug therapy while minimizing risk. As the population continues to age, this paper offers pharmacists some guidance on how to achieve this balance.
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