The addition of radiation therapy to chemotherapy after breast cancer surgery “substantially” improves survival, according to a 20-year followup analysis of a British Columbia trial.

A shorter-term follow-up failed to show a survival benefit with radiation therapy, Dr. Joseph Ragaz, at McGill University Health Center in Montreal, and his colleagues report in the Journal of the National Cancer Institute.

The trial included 318 pre-menopausal women treated with modified radical mastectomy and lymph node removal. The subjects were randomly assigned to radiation and chemotherapy or chemotherapy alone.

After an average follow-up of living patients at 20 years 9 months, the investigators observed significant improvement in several measures in the radiation group compared with the chemo-only group. This included survival rates free of breast cancer of 48 percent versus 30 percent, and overall survival of 47 percent versus 37 percent.

Long-term deleterious effects of radiation appeared to be acceptable, the researchers note, since the rate of non-breast cancer deaths did not differ significantly between groups.

“Our data show that implementing radiation therapy soon after diagnosis ... is important,” Ragaz’s group concludes, because women whose breast cancer recurred and was treated with radiation at the time of relapse “was generally not curable.”

SOURCE: Journal of the National Cancer Institute, January 19, 2005.