Mammogram reveals increased density (arrow) of the right breast. Image source: Indian J Radiol Imaging 2010 May;20(2):98–104.

A “potentially practice-changing” study suggested that additional radiation treatment (RT) improves disease-free survival, lessening the chance of cancer recurring in women with early breast cancer who have had breast-conserving surgery, according to interim results presented at the annual meeting of the American Society of Clinical Oncology (ASCO).

"These results are potentially practice-changing," said Timothy J. Whelan, MD, professor of oncology at McMaster University's Michael G. DeGroote School of Medicine in Hamilton, Ontario.

Treatment for women with node-positive breast cancer has been breast-conserving surgery plus axillary lymph node dissection, followed by radiation to the breast (whole breast radiation, or 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 regional lymph node irradiation (RNI), according to ASCO and American Society of Therapeutic Radiation Oncology guidelines. However, until now, the benefit of adding RNI for women with one to three positive nodes has been unclear.

In the study of more than 1,800 women with breast conserving surgery, participants received WBI alone or WBI plus RNI.

Most of the women had one to three positive lymph nodes while 10 percent 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 percent improvement in disease-free survival for women receiving RNI. This resulted from a 41 percent lower rate of recurrences in the breast and lymph nodes and a 36 percent lower rate of cancer recurrence in other parts of the body.

There was a low, but statistically significant, increased risk of moderate pneumonitis and lymphedema in the arm on the radiated side.

Whelan expects the results 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," added Christine Williams, MD, director of research at Canadian Cancer Society. "Ultimately, this finding will help more women survive and thrive after treatment."