Disparities in the Initial Local Treatment of Older Women with Early-Stage Breast Cancer: A Population-Based Study

Background: Although breast cancer is most prevalent among older women, the majority are diagnosed at an early stage. When diagnosed at an early stage, women have the option of breast-conserving surgery (BCS) plus radiation therapy (RT) or mastectomy for the treatment of early-stage breast cancer (ESBC). Omission of RT when receiving BCS increases the risk for recurrence and poor survival. Yet, a small subset of older women may omit RT after BCS. This study examines the current patterns of local treatment for ESBC among older women. Methods: This study conducted a retrospective observational analysis using the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked dataset of women age ≥66 diagnosed with stage I-II breast cancer in 2003-2009. SEER-Medicare data was additionally linked with data from the Area Resource File (ARF) to examine the association between area-level healthcare resources and treatment. Two logistic regression models were used to estimate how study factors were associated with receiving (1) BCS versus BCS+RT and (2) Mastectomy versus BCS+RT. A stratified analysis was also conducted among women aged <70 years. Results: Among 45,924 patients, 55% received BCS+RT, 23% received mastectomy, and 22% received BCS only. Women of increasing age, comorbidity, primary care provider visits, stage II disease, and nonwhite race were more likely to have mastectomy or BCS only, than BCS+RT. Women diagnosed in 2004-2006, treated by an oncology surgeon, residing in metro areas, areas of greater education and income, were less likely to receive mastectomy or BCS only, than BCS+RT. While women aged <70 years were more likely to receive BCS+RT, socioeconomic and physician specialties were associated with receiving BCS only. Conclusions: Over half of older women with ESBC initially receive BCS+RT. The likelihood for mastectomy and BCS only increases with age, comorbidity, and vulnerable socio-demographic characteristics. Findings demonstrate continued treatment disparities among certain vulnerable populations.