Study may change radiation therapy standards for women with breast cancer

Additional radiation treatment improves disease-free survival, lessening the chance of
cancer recurring in women with early breast cancer who have had breast-conserving
surgery (lumpectomy), interim results of a new study have found.

“These results are potentially practice-changing,” said Dr. Timothy J. Whelan,
professor
of oncology at McMaster University's Michael G. DeGroote School of Medicine and lead
study investigator for the NCIC 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 per cent 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
per
cent improvement in disease-free survival for those receiving RNI. This resulted from a
41 per cent lower rate of recurrences in the breast and lymph nodes and a 36 per cent
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.

Whelan, division head of radiation oncology at McMaster and the Juravinski Cancer
Centre and a Canada Research Chair, 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,” 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 tumour 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 will be presented June 6 at the annual meeting of the American Society
of
Clinical Oncology.