Radiotherapy and CDK inhibitors: Opportunities and risks.

CDK4/6 inhibitors are nowadays commonly used in metastatic HR+/HER2- breast cancer. Herein, we report a literature review regarding the benefits and risks of their combination with radiotherapy. Numerous pre-clinical studies have indeed shown a potential synergistic effect of these treatments in combination with radiotherapy in various types of cancers. On the other hand, some retrospective clinical studies have reported increased acute toxicity in case of digestive or pulmonary irradiation; therefore, it is advisable to discontinue CDK4/6 inhibitors before starting irradiation. Several prospective clinical trials are currently ongoing to assess the feasibility of this combination.

[Extreme hypofractionation: New indications for breast cancer radiotherapy]. / Hypofractionnement extrême en pratique : les nouvelles indications dans les cancers du sein.

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.