Radiation therapy is effective in treating breast cancer but typically requires dozens of visits over five to seven weeks. A newer protocol takes just three weeks. Antonia Reeve/Science Source hide caption itoggle caption Antonia Reeve/Science Source Shots - Health News Doctors Lag In Adopting Cheaper, Faster Radiation For Breast Cancer December 10, 2014 Three weeks of radiation works just as well as six weeks for most women with early stage breast cancer. But doctors have been slow to make that switch. Money may be one big reason why, a study says.