Radiation has long played a role in the treatment of breast cancer, though doctors have used it more sparingly in early-stage disease in recent years, as advances in diagnostics and treatment have improved survival rates.
Now a new study with an unusually long follow-up period has found that radiation to the chest wall made absolutely no difference in survival among women with early-stage breast cancer who had been treated with mastectomy, lymph-node surgery and advanced anti-cancer drugs.
The results of the large, randomized clinical trial were published on Thursday in The New England Journal of Medicine.
The women in the study were at intermediate risk, meaning they had Stage II cancer with one to three affected lymph nodes, or tumors with aggressive features and no lymph node involvement. Most of the patients had not had chemotherapy before their surgeries, which reduces the need for radiation, Dr. Kunkler added.
The results support a trend already underway, he said, “toward de-escalation of radiotherapy in lower-risk groups of patients.” The risks to these women are low enough, and chemotherapy effective enough, to obviate the need for radiation.
“We’ve now shown that with contemporary anti-cancer treatments, the risk of recurrence is very, very low — sufficiently low to avoid radiotherapy in most patients,” said Dr. Ian Kunkler, chief investigator of the international trial and a lead author of the paper.
The trial included over 1,600 women with early-stage disease, half of whom had received radiation treatment and half of whom had not. After researchers followed them for a median of 9.6 years, survival rates were similar: 81.4 percent among the patients who had received radiation treatment, and 81.9 percent among those who had not.
Radiation had no impact on the amount of time the women lived without a recurrence, and no effect on whether disease spread from the breast to other parts of the body.
Still, those who had received radiation treatment were at significantly lower risk of having a cancer recurrence in the chest wall. But the number of recurrences was very small: Of 29 patients who had one, nine (or 1.1 percent) had received radiation, and 20 (or 2.5 percent) had not.
Even though radiation is already being used less often among lower-risk patients, the findings will help clarify treatment for women at intermediate risk.
“It was clear for low-risk cancer that you did not need radiation after mastectomy and that for high-risk patient you did need radiation and still do it after mastectomy,” said Dr. Harold Burstein, a medical oncologist at Dana Farber Cancer Institute and a professor at Harvard Medical School, who was not involved in the study.
“That left open the question of the intermediate group of patients — there was still a question of whether adding radiation therapy would be helpful,” he said. The study results suggests that radiation is not necessary for these women.
“We know that almost all patients experience some side effects of radiotherapy that can develop even years after treatment,” said Dr. Nicola Russell, one of the lead authors of the trial, which was carried out by the Medical Research Council, the European Organization for Research and Treatment of Cancer and Breast International Group.
In the short term, radiation can cause sunburn-like effects and other changes in the skin, as well as soreness and swelling. In rare cases, it can lead to lung inflammation and may also increase the risk of lymphedema, a condition that causes swelling in the arms and can be serious.
Radiation also can complicate breast reconstruction immediately after mastectomy surgery, as well as later reconstruction, because it changes the texture of the skin, making it less elastic and more prone to scarring.
Patients at higher risk of recurrence and spreading of cancer may still benefit from radiation, the researchers cautioned.
Roni Caryn Rabin is a Times health reporter focused on maternal and child health, racial and economic disparities in health care, and the influence of money on medicine.
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