PURPOSE: Examination of Geoffrey Keynes's contributions to brachytherapy and the management of breast cancer.

METHODS AND MATERIALS: Review of publications and texts of the era.

RESULTS: In an era when radical mastectomy was accepted as standard treatment for breast cancer, Keynes demonstrated that brachytherapy (with or without local excision) was equally effective, while sparing body form and function.

CONCLUSIONS: Keynes established that conservative surgery, combined with radiotherapy, was the preferable option for managing breast cancer.