Foregoing Radiotherapy after Breast Conserving Surgery

Patients with cancer often question whether the risks and adverse effects associated with a specific treatment outweigh the benefits. This decision is highly personal and dependent on individual values and goals. Many patients value independence and quality of life over cancer recurrence and rely on physicians to recommend treatments that align with those goals.

Although radiotherapy after breast conserving surgery is usually well tolerated, adverse effects include telangiectasia, breast pain, induration, retraction, and rarely secondary cancers and ischemic cardiac disease. Some women at low risk for local recurrence may forego radiation therapy, but outcome studies are needed to predict the effect on recurrence risk.

Investigators of the prospective LUMINA cohort study examined the incidence of local recurrence associated with omitting radiotherapy following breast conserving surgery and endocrine therapy in a subset of 500 women with a new diagnosis of low-risk invasive breast cancer. The women were ≥55 years of age, had a primary tumor < 2 cm in diameter, negative axillary nodes, and luminal A breast cancer, which is the least proliferative and associated with the best prognosis.

At 5 years, the incidence of local recurrence associated with the omission of radiotherapy was 2.3% (90% confidence interval, 1.3 to 3.8). This rate will likely increase after longer follow up. In a recent study and a study published in 2013, 10-year recurrence rates approximated 10% in patients with early breast cancer who had omitted radiotherapy. Therefore, longer follow up of the Lumina study is needed to guide patient-physician conversations regarding long-term risks of foregoing radiotherapy, as many breast cancer survivors now live 20 to 30 years after treatment, even those diagnosed at a relatively older age. In the meanwhile, women with low-risk breast cancer who are aged 55 years and older can use these data to help inform decisions about whether to include radiotherapy in their treatment plan.

Read the following NEJM Journal Watch summary for more details of this study.

William J. Gradishar, MD, reviewing Whelan TJ et al. N Engl J Med 2023 Aug 17

Breast radiation to reduce risk of local recurrence has been a standard of care for women undergoing breast conserving surgery for invasive cancer. Certain subsets of patients, including older women, have been identified who may be able to avoid radiation therapy, with no compromise in overall outcome (NEJM JW Oncol Hematol Feb 12 2023 and N Engl J Med 2023; 388:585). Another approach being explored is identifying molecular subsets of breast cancer that may not require radiation therapy in the setting of breast conservation.

The LUMINA prospective cohort study enrolled 500 women ≥55 years old with T1N0, luminal A-subtype breast cancer who had undergone breast-conserving surgery. Patients received adjuvant endocrine therapy with no radiation therapy. Eligible tumors were estrogen receptor-positive (≥1%), progesterone receptor-positive (>20%), and HER2-negative, and had Ki-67 index ≤13.25%. Ductal, tubular, and mucinous histology was allowed, whereas lobular carcinoma was not.

Patients were followed clinically every 6 months for 2 years and annually thereafter. Annual mammograms were obtained, and patients were interviewed about adherence to adjuvant endocrine therapy. Patients' median age was 67 years; only 12% were aged 75 and older. The median tumor size was 1.1 cm. Adjuvant endocrine therapy was an aromatase inhibitor in 59% of patients and tamoxifen in 41%.

At 5 years, the rate of local recurrence in the ipsilateral breast was 2.3% (10 patients), which met the trial's prespecified boundary of ≤5%.

Comment: This study identifies a group of patients with early-stage breast cancer with favorable features who can safely defer radiation therapy. The study included younger patients than prior studies, thus expanding the population of patients with favorable features who can safely avoid radiation therapy. Inevitably, with longer follow-up there will be additional ipsilateral recurrences, but these results support a more refined approach to adjuvant radiation therapy.

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Abigail Schubach, MD, is a 2023–2024 NEJM Editorial Fellow. She is currently an internal medicine hospitalist at Brigham and Women’s hospital. She completed her internal medicine residency at University of Rochester.