Omission of radiation therapy following breast conservation in older (≥70 years) women with T1-2N0 triple-negative breast cancer

Background: Although randomized data support omitting adjuvant radiotherapy (RT) following breast conservation for T1-2N0 estrogen receptor positive breast cancer in ≥70-year-old women, there remains a knowledge gap regarding its omission for triple-negative BC (TNBC). Methods and materials: The National Cancer Database (NCDB) was queried for ≥70-year-old females with newly diagnosed T1-2N0M0 TNBC treated with breast conservation. Multivariable logistic regression ascertained factors associated with adjuvant RT administration. Overall survival (OS) between patients treated with or without adjuvant RT was estimated using the Kaplan-Meier method. Cox proportional hazards modeling determined variables associated with OS. Results: Of 8526 patients, 6283 (74%) patients received adjuvant RT, and 2243 (26%) did not. RT was more frequently withheld in older patients, those with higher comorbidities, lower income, pT2 disease, following margin-positive resection, receipt of chemotherapy, and at academic centers (P < 0.05 for all). Median follow-up was 38.0 months. Five-year OS was greater in the adjuvant RT group (77.2% vs 55.3%, P < 0.001); these differences persisted when stratifying for age, T stage, and chemotherapy utilization (P < 0.001 for all). Omission of RT was also independently associated with poorer OS on multivariate analysis (P < 0.001). Conclusions: This investigation, the largest known such study to date, observed that omission of adjuvant RT for elderly women with T1-2N0 TNBC was associated with poorer OS; this was observed across a range of age groups, as well as following stratification by T stage and chemotherapy usage. Although these results do not imply causation, caution must be exercised when considering omission of adjuvant RT in node-negative TNBC patients.