After cancerous breast tissue is removed, radiation treatments are given to prevent the cancer from coming back. Standard therapy has been five weeks of daily treatment.
A study presented to the "San Antonio Breast Cancer Symposium" finds shorter treatments may be just as good.
Scientists followed almost 4500 women for 10 years.
Those who received three weeks of radiation in slightly larger doses had the same rate of cancer relapse as those who had the five-week course.
The shorter treatment can save time and money for patients and for healthcare providers.