Background: Women >70 years old with T1N0 hormone receptor-positive (HR+) breast cancer face complex locoregional therapy decisions, as breast surgery type, and omission of axillary surgery or radiation therapy (RT), do not impact overall survival. Although frailty status and life expectancy (LE) ideally factor into therapy decisions, their impact on decision-making is unclear. We sought to identify trends in, and factors associated with locoregional therapy type by frailty and LE, and to determine if therapy type was associated with cause of death. Methods: Women >70 years old with T1N0 HR+/HER2-negative breast cancer diagnosed 2010-2015 were identified in SEER-Medicare. Stratified by validated claims-based frailty (Kim et al) and LE (Tan et al) measures, trends in therapy (lumpectomy, lumpectomy + axillary surgery, lumpectomy + RT, mastectomy, lumpectomy + axillary surgery + RT, and mastectomy + axillary surgery, with the last two combinations deemed “more intense” therapy) were analyzed. Generalized linear mixed models were used to identify factors associated with therapy receipt (breast surgery type, axillary surgery, and RT) and, among the women who died in this cohort, to explore potential associations between local therapy received and cause of death. Results: Of the 16,188 women included, 21.8% were frail, 22.2% had a LE<5 years, but only 12.3% were both frail and had a LE<5 years. In frail women who had a LE < 5 years, more intense therapy regimens decreased significantly (lumpectomy + axillary surgery + RT: 27.5% to 17.3%, p<0.001; mastectomy + axillary surgery: 20.8% to 13.9%, p=0.02) over the study period. However, in 2015, 30% of frail women with a LE<5 years still underwent a more intense regimen. On multivariable analysis, frailty and LE<5 years were associated with a lower likelihood of axillary surgery (frailty: OR 0.65, 95% CI [0.57-0.73]; LE<5 years: OR 0.67, 95% CI [0.59-0.76]) and RT (frailty: OR 0.77, 95% CI [0.69-0.86]; LE<5 years: OR 0.73, 95% CI [0.65-0.83]), but not with breast surgery type. Of the 1868 women who died, 306 (16.4%) died of breast cancer and those undergoing more intense therapy were as likely to die of breast cancer vs other causes (Table). Conclusions: In older women with T1N0 HR+ disease, rates of more intense therapy are decreasing but 30% of frail women with a limited LE still underwent more intense therapy in the final study year. As therapy intensity does not affect breast cancer-specific mortality, appropriate de-escalation of locoregional therapy is needed.

Adjusted for frailty, LE, diagnostic year, race/ethnicity, income, SEER region, tumor grade, stage, histology.