How Best to Use Radiotherapy for Early-Stage Breast Cancer: 30-Year Trial Update Offers Clues

By: Celeste L. Dixon
Posted: Wednesday, August 28, 2024

Findings from a 30-year update of the randomized, controlled, 585-patient phase III Scottish Breast Conservation Trial suggest that “patients whose biology predicts a late relapse a decade or more after breast-conserving surgery for early breast cancer might gain little from adjuvant radiotherapy.” This hypothesis should be tested using longer-term follow-up of similar contemporary trials, according to Linda J. Williams, PhD, of the University of Edinburgh, and colleagues in The Lancet Oncology.

“Our evidence suggests that radiotherapy protects against cancer returning in the same breast for up to 10 years,” stated study coauthor Ian H. Kunkler, MB, BChir, of the University of Edinburgh’s Institute of Genetics and Cancer, in a press release. “Like other anticancer treatments, radiotherapy loses its beneficial effects in the long term.”

With a median follow-up of 17.5 years, no significant difference in overall survival emerged between patients who did not receive radiotherapy and those who did (median, 18.7 vs 19.2 years; P = .43). Although numerous randomized trials have compared breast-conserving surgery with or without radiotherapy, few other reports of clinical outcomes beyond the first decade of follow-up have appeared, they noted. Still, breast-conserving surgery followed by adjuvant systemic therapy and radiotherapy remains the standard of care for most women with early-stage breast cancer.

This trial included women up to age 70 with early-stage breast cancer (tumors ≤ 4 cm; T1 or T2 and N0 or N1) who underwent breast-conserving surgery between 1985 and 1991. Estrogen receptor (ER)-rich patients received tamoxifen daily for 5 years, whereas ER-poor patients received eight courses of chemotherapy. The patients were then stratified by ER status and by menstrual status (within or more than 12 months from last menstrual period) and randomly assigned to receive high-dose local or locoregional radiotherapy (n = 291) vs no radiotherapy (n = 294).

Along with overall survival, the original trial’s co-primary endpoint was ipsilateral breast tumor recurrence. This recurrence rate was, in fact, significantly lower in the first decade after treatment in the radiotherapy group (16% vs 36% in the no-radiotherapy group; P < .0001). Of note, however, declared Dr. Williams and co-investigators, subsequent risks of that recurrence were similar (P = .95).

Disclosure: For full disclosure of the study authors, visit thelancet.com.

The Lancet Oncology