Survival Outcomes of Early-Stage Hormone Receptor-Positive Breast Cancer in Elderly Women

Abstract

Background: Elderly women (≥ 70 years old) form a significant proportion of patients affected by breast cancer (BC); however, the treatment decisions for this patient population are complicated, owing to the presence of comorbidities, limited life expectancy, reduced tolerability of therapy, and limited enrollment in clinical trials. A growing body of evidence suggests equivalent outcomes in elderly patients with hormone receptor-positive early-stage breast cancer receiving primary endocrine therapy only or surgery with subsequent endocrine therapy. Whether these results are reproduced in the larger BC population outside of a clinical trial currently remains unclear.

Patients and methods: Women ≥ 70 years old diagnosed with early-stage invasive breast cancer between January 2008 and December 2013 with tumor size T1 or T2, minimal nodal involvement (N0 and N1), and estrogen and/or progesterone receptor positivity who started endocrine therapy within a year of diagnosis were identified using the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked datasets. Endocrine therapy was identified using outpatient prescription fills for anastrozole, exemestane, fulvestrant, letrozole, raloxifene, tamoxifen, and toremifene; the first fill date was used as the treatment initiation date. Surgical intervention included either breast-conserving surgery or mastectomy. Women who received chemotherapy were excluded. Trends in the use of primary endocrine therapy only were assessed using Poisson regression. Multivariable Cox proportional hazard regression was used to estimate the association between undergoing surgery within a year of diagnosis and 5-year all-cause mortality, after adjusting for patient demographics, comorbidities, and clinical cancer characteristics. Similar methods were used to assess 5-year cancer-specific mortality, where noncancer mortality was treated as a competing risk.

Results: Overall, 8784 women were included in the analysis: 8006 (91%) received surgery with endocrine therapy and 778 (9%) received primary endocrine therapy alone. The proportion of women not receiving surgery remained consistent between 2008 and 2013 (p = 0.10). The 5-year mortality was 11% (n = 619), and 19% of all deaths were due to cancer causes (n = 117). After adjustment, 5-year mortality was lower among women undergoing surgery (HR 0.59, 95% CI 0.47-0.74, p < 0.0001). Similar results were found when looking at 5-year cancer-specific mortality (HR 0.52, 95% CI 0.30-0.90, p < 0.0001).

Conclusions: Elderly breast cancer patients with early-stage hormone-receptor-positive disease receiving primary surgical intervention plus endocrine therapy may have significantly improved survival than those receiving primary endocrine therapy alone. This study suggests the importance of surgical intervention for elderly breast cancer patients and warrants further investigation and comprehensive geriatric assessment to identify subsets of elderly breast cancer patients who may benefit significantly from surgical intervention.