Radiotherapy after mastectomy can be avoided

An international trial, led by researchers at the Institute of Genetics and Cancer and Netherlands Cancer Institute, found that patients with early-stage breast cancer who underwent a mastectomy – removal of the breast – had similar 10-year survival rates whether or not they received radiotherapy.

Experts say the findings should help guide treatment discussions, as many patients who currently qualify for radiotherapy after mastectomy under existing guidelines may not actually need it.

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The practice is based on trials from the 1980s, now considered outdated, leaving uncertainty about its benefit and leading to variation in use worldwide.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) studied the impact of chest wall radiotherapy in patients at intermediate risk of breast cancer returning. 

The group included women from 17 countries with one to three affected lymph nodes, as well as those with none but who had other tumour features of aggressive behaviour that increase the chance of recurrence.

All 1,607 patients in the study underwent mastectomy, axillary surgery – removing lymph nodes from the armpit – and 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 per cent of those who received radiotherapy were still alive, compared with 81.9 per cent 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.

Radiotherapy had minimal impact on cancer recurring at the site of mastectomy. Nine patients who received the treatment saw their breast cancer return on the chest wall, compared with 20 who did not. Side effects from radiotherapy were mild with no excess deaths reported from cardiac causes.

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. The international research team included scientists from the UK, Netherlands, Australia and China.

The study was funded by a Medical Research Council (MRC) and National Institute for Health and Care Research (NIHR) partnership, EORTC, Dutch Cancer Society, Cancer Australia, Breast Cancer Institute, Edinburgh Cancer Centre and HSBC Trustees. It was jointly sponsored by the University of Edinburgh, NHS Lothian and Public Health Scotland.