Women at high risk of recurring breast cancer who receive radiation in addition to a mastectomy and chemotherapy have better survival rates, say Canadian researchers.

The discovery comes from an analysis of 20 years of data from 318 British Columbia premenopausal breast cancer patients.

It shows that those with radiation of both their chest wall and the surrounding areas containing lymph nodes had better survival rates with few long-term side-effects, compared to half the women who had chemotherapy alone after surgery.

Women with large tumours and those whose cancer has spread to three or more lymph nodes are considered high risk.

The study appears in Wednesday's Journal of the National Cancer Institute. It found that when radiation was used after surgery and chemotherapy, there was a 32 per cent reduction in the death rate from breast cancer.

Radiation can damage the heart and increase the risk for lymphodema, a painful and often permanent swelling of the arm on the side where lymph nodes have been removed.

Lead author Dr. Joseph Ragaz, of the McGill University Health Centre, along with his fellow researchers, concluded that "long-term toxic effects, including cardiac deaths, were acceptable for both groups of patients."

In a commentary accompanying the study, Dr. Timothy Whelan and Dr. Mark Levine of the Juravinski Cancer Centre in Hamilton noted doctors should take into account changes in treatment over the last 20 years, such as the move to lumpectomies from mastectomies.