[Extreme hypofractionation: New indications for breast cancer radiotherapy].

Due to the continuously increasing number of newly diagnosed breast cancer and limited health resources hypofractionated radiotherapy is a major topic. Recent results from randomized clinical trials assessing extreme hypofractionated radiotherapy for whole or partial breast radiotherapy are practice changing. Here we report toxicity and oncological outcomes from major recent trials of extreme hypofractionated breast irradiation and present an ongoing prospective implementation program. For whole breast irradiation, with a 10 years follow up, the UK-FAST trial demonstrated no significant difference in toxicity between a once weekly 5 fractions (5,7Gy/fr) regimen and a conventional 50Gy/25fr regimen. With a 5 years follow up, the FAST-Forward trial showed non inferiority on local control for a 5 fractions over 1 week (5,2Gy/fr) regimen versus standard 40Gy/15fr over 3 weeks with safe toxicity profile. For accelerated partial breast irradiation, in low-risk breast cancers patients, several phase III randomized trials confirmed that extreme hypofractionation is a valid option. With our "One Week Breast Radiotherapy" program, we propose the implementation of a one-week full workflow preparing and delivering 5 fractions over 1 week (26Gy) in selected patients with prospective follow-up. Several extreme hypofractionated breast radiotherapy regimens are validated and can be routinely discussed with patients in a share decision-making process following patient selection criteria and dosimetric constraints.