Omitting radiotherapy in women ≥ 65 years with low-risk early breast cancer after breast-conserving surgery and adjuvant endocrine therapy is safe.

Purpose: The aim of this study was to verify if radiotherapy (RT) safely can be omitted in older women treated for estrogen-receptor positive early breast cancer with breast-conserving surgery (BCS) and endocrine therapy (ET).

Patients And Methods: Eligibility criteria were: consecutive patients with age ≥65 years, BCS + sentinel node biopsy, clear margins, unifocal T1N0M0 breast cancer tumor, Elston-Ellis histological grade 1 or 2 and estrogen receptor-positive tumor. After informed consent, adjuvant ET for 5 years was prescribed. Primary endpoint was ipsilateral breast tumor recurrence (IBTR). Secondary endpoints were contralateral breast cancer and overall survival.

Results: Between 2006 and 2012, 603 women were included from 14 Swedish centers. Median age was 71.1 years (range 65-90). After a median follow-up of 68 months 16 IBTR (cumulative incidence at five-year follow-up; 1.2%, 95% CI, 0.6% to 2.5%), 6 regional recurrences (one combined with IBTR), 2 distant recurrences (both without IBTR or regional recurrence) and 13 contralateral breast cancers were observed. There were 48 deaths. One death (2.1%) was due to breast cancer and 13 (27.1%) were due to other cancers (2 endometrial cancers). Five-year overall survival was 93.0% (95% CI, 90.5% to 94.9%).

Conclusion: BCS and ET without RT seem to be a safe treatment option in women ≥ 65 years with early breast cancer and favorable histopathology. The risk of IBTR is comparable to the risk of contralateral breast cancer. Moreover, concurrent morbidity dominates over breast cancer as leading cause of death in this cohort with low-risk breast tumors.