For many patients with early-stage breast cancer treated by mastectomy and anti-cancer drugs, chest wall radiotherapy has long been standard to kill any remaining cancer cells and lower the risk of recurrence. The practice is based on trials from the 1980s, now considered outdated, leaving uncertainty about its benefit and leading to variation in use worldwide.
The SUPREMO trial (Selective Use of Postoperative Radiotherapy after Mastectomy), led by the University of Edinburgh, studied the impact of chest wall radiotherapy in patients at intermediate risk of breast cancer returning.
The group included women from 161 hospitals across 17 countries with one to three affected lymph nodes, as well as those with none but who had other tumor features of aggressive behavior that increase the chance of recurrence. All 1,607 patients in the study underwent mastectomy, surgery to remove lymph nodes from the armpit and received modern anti-cancer therapy. They were randomly assigned to chest wall radiotherapy (808 women) or no radiotherapy (799).
There was no difference in overall survival of patients after ten years of follow up: 81.4% of those who received radiotherapy were still alive, compared with 81.9% of those who did not. Radiotherapy also had no impact on disease-free survival – the length of time without any cancer returning – or on the cancer spreading from the breast around the body, the study found.
Nicola Russell, radiotherapist and study coordinator on behalf of the EORTC, said: “Although reported toxicity in the trial was mild, we know that almost all patients experience some side effects of radiotherapy, which can develop even years after treatment. Avoiding unnecessary irradiation will reduce both treatment burden and, for example, the detrimental effects on breast reconstruction for these mastectomy patients.”
Experts attribute radiotherapy providing less benefit than previously thought to progressive improvements in treatment, particularly better drug treatments, which continue to reduce the chances of the cancer returning, and boost survival rates.
The research team caution that the study only looked at those with intermediate-risk breast cancer. Patients with a higher risk of their cancer returning could possibly benefit from chest wall radiotherapy, they add.
The study is published in the New England Journal of Medicine: https://www.nejm.org/doi/full/10.1056/NEJMoa2412225. The international research team included scientists from the UK, Netherlands, Australia and China.
Research at the Netherlands Cancer Institute is financially supported by KWF Dutch Cancer Society and the AVL Foundation.