Is Radiation Necessary After Surgery for Patients With Low-Risk Breast Cancer?

By: Chris Schimpf, BS
Posted: Tuesday, September 19, 2023

Radiotherapy following breast-conserving surgery may not be necessary for some patients with low-risk breast cancer, according to research published recently in The New England Journal of Medicine. Timothy J. Whelan, BM, BCh, of McMaster University and Juravinski Cancer Centre at Hamilton Health Sciences, Ontario, and colleagues found in their multicenter, prospective cohort study that among women aged 55 or older who had T1N0, grade 1 or 2 luminal A breast cancer, the risk of local recurrence at 5 years was very low following breast-conserving surgery and endocrine therapy alone.

A total of 500 patients were enrolled in the study, all of whom were at least 55 years of age and had undergone breast-conserving surgery for T1N0, grade 1 or 2, luminal A–subtype breast cancer with node-negative tumors of less than 2 cm. The researchers used the Ki67 molecular test to assess the tumor growth rates of prospective participants. They defined the luminal A subtype as having estrogen receptor positivity of at least 1%, progesterone receptor positivity of more than 20%, negative human EGFR 2, and a Ki67 index of up to 13%.

“Adding the simple and affordable Ki67 test allows us to identify patients who can avoid the inconvenience and side effects of breast radiation,” said Sally Smith, MD, Western Canada regional lead for the study, in a McMaster press release. “This, indirectly, helps to ensure resources are directed to patients who benefit from radiation therapy.”

“This is a major advance in our treatment approach for breast cancer,” said Dr. Whelan.

At 5 years after surgery, the investigators observed local recurrence in 2.3% of the participants (90% confidence interval [CI] = 1.3%–3.8%; 95% CI = 1.2%–4.1%). They reported that breast cancer occurred in the contralateral breast in 1.9% of the patients (90% CI = 1.1%–3.2%) and that recurrence of any type occurred in 2.7% (90% CI = 1.6%–4.1%).

Disclosure: For full disclosures of the study authors, visit nejm.org.

The New England Journal of Medicine