Women who have their breasts removed because of cancer may benefit from receiving radiation if they still have traces of cancer in their lymph nodes, suggests a new analysis.

Radiation reduced the risk of death and of cancer returning among women who had cancer cells detected in the cluster of nodes under the arms after a mastectomy. The nodes are part of the lymphatic system, a conduit for immune and other cells.

“It has been clear for some time that women in whom the disease has not spread to the lymph nodes in the armpits will not benefit from radiotherapy,” Sarah Darby told Reuters Health.

“It’s been unclear what the benefit is for women with one, two or three positive lymph nodes,” she said.

Darby is one of the study’s authors from the Early Breast Cancer Trialists’ Collaborative Group at the University of Oxford in the UK.

The new findings are based on data from over 8,000 women who were randomly assigned to either receive radiation or not after having one or both breasts removed because of cancer. The data were from 22 trials conducted between 1964 and 1986.

The researchers, who published their results in The Lancet, had information about whether the women were diagnosed with breast cancer again within about 10 years of receiving radiation. They also knew whether the women had died by the start of 2009.

They confirmed what had been known - that radiation did not offer any benefits for women who had no lymph nodes test positive for cancer after their mastectomy.

But for women who had one to three lymph nodes test positive after their breasts were removed, they did find a noticeable difference in cancer recurrence and death.

For example, women with positive lymph nodes had about a 46 percent risk of their breast cancer returning during the 10 years after their breasts were removed. That risk fell to about 34 percent over 10 years among women who received radiation.

Similarly, about 47 percent of the women who did not receive radiation died of breast cancer by the start of 2009. That compared to about 37 percent of women who received radiation.

Women who received radiation were also less likely to die from any cause, compared to those who did not get radiation.

The benefits of radiation remained even among women who received other treatments, such as chemotherapy.

“This actually will confirm a lot of what people started to think about,” Dr. Alphonse Taghian told Reuters Health.

He wasn’t involved in the new study but is co-director of the Breast Cancer Research Program and chief of breast radiation oncology at Massachusetts General Hospital in Boston. He also teaches at Harvard Medical School.

“My sense is that there is a majority of physician oncologists who would use post-mastectomy radiation in patients with one to three positive lymph nodes,” Taghian said.

“There will still be cases that we’ll agonize about and it’s not really clear cut, but there is no doubt that this study will make an impact on how people think about the one to three positive lymph nodes,” he said.

Most professional guidelines do not recommend radiation for women with one to three lymph nodes that test positive for cancer, Darby said.

“I hope people will review the guidelines,” she said. “I would certainly expect the guidelines to change.”

Due to the age of the data included in the study, however, there are some caveats.

Specifically, the women included in this analysis had their lymph nodes sampled or completely removed to see how many contained cancer. Those procedures are not commonly used now.

Also, Taghian said, it’s also important for people to know that while radiation can cause heart problems or other cancers, the technology has improved.

“We are more precise,” he said. “We are able to protect tremendously the tissue which doesn’t need to be exposed to radiation and we have a better understanding and knowledge of the biology of the tumor. This should reduce the risk of having major complications.”

Dr. Philip Poortmans wrote in an accompanying editorial that the results of the new analysis “clearly confirm” that post-mastectomy radiation should be considered for patients with one to three lymph nodes that test positive for cancer.

He is with the Department of Radiation Oncology at the Institute Verbeeten in Tilburg, Netherlands.

Darby said it’s important for women to talk with their doctors about their treatment options.

“Breast cancer is a very complicated disease,” she said. “In each individual case it would be very hard for the patient to know what’s best. I would counsel women to talk about it with their oncologists.”

SOURCE: The Lancet, online March 19, 2014

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