Background
Randomized trials support the omission of radiation therapy (RT) after breast-conserving surgery (BCS) in selected older women with early-stage estrogen receptor (ER)–positive breast cancer. However, the real-world adoption and long-term outcomes of RT omission in population-based practice remain incompletely characterized.
Materials and Methods
Using the Surveillance, Epidemiology, and End Results database, we carried out population-based cohort research from 2000 to 2022. Women aged greater than or equal to 70 years with stage I, ER-positive invasive breast cancer treated with BCS were included. Patients were categorized by receipt of adjuvant beam radiation vs no radiation; cases with ambiguous radiation status were excluded. Kaplan-Meier techniques and multivariable Cox proportional hazards models adjusted for age, race/ethnicity, tumor size, grade, progesterone receptor status, and year of diagnosis were used to assess overall survival (OS) and breast cancer-specific survival (BCSS).
Results
Of the 50,845 patients who satisfied the inclusion criteria, 32,540 (64%) had adjuvant radiotherapy and 18,304 (36%) did not. In line with known practice changes, trends across time revealed an increase in omission rates from roughly 25% in the early 2000s to over 40% in the most recent timeframe (2018-2022). Radiation was linked to a slightly better OS (adjusted HR [aHR], 0.80; 95% CI, 0.75-0.86) with a median follow-up of roughly 10 years, but there was no statistically significant difference in BCSS between groups (aHR, 0.95; 95% CI, 0.87-1.04). Subgroup studies showed that patients with tumors less than 1 cm and those older than 80 years had comparable BCSS results. According to findings from randomized trials, there were few deaths in this cohort that were specifically related to breast cancer, and most deaths in both groups were linked to non-breast cancer reasons.
Conclusion
In this large population-based cohort study, omission of radiation after BCS in older women with stage I ER-positive breast cancer was not associated with inferior BCSS, although radiation was associated with modest OS differences likely driven by competing mortality. These findings support selective radiation de-escalation in appropriately chosen older patients in routine clinical practice.
