New Findings May Change Radiation Therapy Standards for Women with Breast Cancer

“These results are potentially practice-changing,” said Dr. Timothy J. Whelan, professor of oncology at McMaster University’s Michael G. DeGroote School of Medicine (Hamilton, ON, Canada) and lead study investigator for the NCIC [National Cancer Institute of Canada] Clinical Trials Group, funded by the Canadian Cancer Society.

In the study of more than 1,800 women who have undergone breast-conserving surgery, participants received whole breast radiation (WBI) alone or WBI plus radiation to the surrounding lymph nodes, called regional lymph node irradiation (RNI). Most of the women had one to three positive lymph nodes while 10% had high-risk, node-negative breast cancer. All had been treated with breast-conserving surgery and adjuvant chemotherapy or endocrine therapy.

After a five-year follow-up, interim analysis of the data showed a greater than 30% improvement in disease-free survival for those receiving RNI. This resulted from a 41% lower rate of recurrences in the breast and lymph nodes and a 36% lower rate of cancer recurrence in other parts of the body. There was a low, but statistically significant, increased risk of moderate pneumonitis (lung inflammation) and lymphedema (excess lymphatic fluid) in the arm on the radiated side.

Dr. Whelan, division head of radiation oncology at McMaster and the Juravinski Cancer Center and a Canada Research Chair, expects the study’s findings will encourage physicians to offer all women with node-positive disease the option of receiving regional nodal irradiation. “Adding regional nodal irradiation improved disease-free survival, lowered the risk of recurrences, and there was a positive trend toward improved overall survival, while not greatly increasing toxicities,” he said.

“For women with node positive breast cancer who are at high risk of recurrence of their breast cancer, these findings provide an important new treatment option,” said Dr. Christine Williams, director of research at the Canadian Cancer Society. “Ultimately, this finding will help more women survive and thrive after treatment.”

Treatment for women with node-positive breast cancer has been breast-conserving surgery plus axillary lymph node dissection, followed by radiation to the breast (WBI). If a woman’s cancer is considered high-risk, such as a tumor larger than 5 cm or more than three positive axillary nodes, she often receives RNI. However, until now, the benefit of adding RNI for women with one to three positive nodes has been unclear.

The results were presented June 6, 2011, at the annual meeting of the American Society of Clinical Oncology, held in Chicago, IL, USA.

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McMaster University’s Michael G. DeGroote School of Medicine