Posted: Wednesday, March 29, 2023
The phase III PRIME II trial, conducted by Ian H. Kunkler, MB, BChir, MA, FRCR, of the Institute of Genetics and Cancer, University of Edinburgh, and colleagues, aimed to determine whether the omission of radiotherapy after breast-conserving surgery impacts clinical outcomes among women with early breast cancer receiving endocrine therapy. The 10-year outcomes of this phase III trial were published in The New England Journal of Medicine.
“Omission of radiotherapy was associated with an increased incidence of local recurrence but had no detrimental effect on distant recurrence as the first event or overall survival among women 65 years of age or older with low-risk, hormone receptor–positive early breast cancer,” the investigators concluded. “Our trial provides robust evidence indicating that irradiation can be safely omitted in [this patient population], provided that they receive 5 years of adjuvant endocrine therapy.”
The study authors enrolled 1,326 women aged 65 or older with hormone receptor–positive, node-negative, early-stage primary breast cancer who were treated with breast-conserving surgery. Participants were randomly assigned to receive whole-breast irradiation at 40 or 50 Gy (n = 658) or no irradiation (n = 668).
At the median follow-up of 9.1 years, the cumulative incidence of local breast cancer recurrence within 10 years in the no-radiotherapy and radiotherapy groups were 9.5% and 0.9%, respectively (P < .001). Even though the 10-year incidence of distant recurrence as the first event was not significantly higher in the no-radiotherapy group compared with the radiotherapy group (1.6% vs. 3.0%), local recurrence occurred more frequently in the no-radiotherapy group.
Furthermore, the no-radiotherapy and radiotherapy groups had similar rates of overall survival at 10 years, at 80.8% and 80.7%, respectively; disease-free survival rates were 68.9% and 76.3%. Additionally, the rates of breast cancer–specific survival were nearly identical between the two groups (97.4% vs. 97.9%).
Disclosure: For full disclosures of the study authors, visit nejm.org.
The New England Journal of Medicine