If previous observations are valid and breast irradiation following tylectomy exerts its maximal effect in eradicating occult disease remaining in the immediate vicinity of the tylectomy site, can radiation therapy be directed only to the tissue surrounding the excision cavity of the breast, using brachytherapy alone? If so, the entire course of radiation therapy could be delivered over a 4 to 7 day period immediately following tylectomy and/or axillary dissection, thus markedly reducing treatment time. Brachytherapy also inherently provides a higher central dose to the volume most at risk for recurrence. Cosmetic outcome after the use of a brachytherapy boost after external whole breast radiotherapy is comparable or slightly inferior to electron beam boost radiation therapy