Fractionating Boost Dose in Postoperative Breast Radiotherapy

Mild hypofractionation in postoperative breast radiotherapy (RT) is now widely accepted as the preferred treatment, especially after the publication of the START trials in the United Kingdom. A boost to postoperative whole-breast irradiation (WBI) is indicated in selected patients to further reduce the risk of local recurrence. However, the exact dose and fractionation of radiation boost are subject to clinical debate. In the present work, we calculated the biologically effective doses (BEDs, linear-quadratic model) of WBI and boost RT prescribed in the most cited clinical trials to suggest an acceptable trial-based dose and fractionation for boost RT. WBI of a BED value of 65-75 Gy_3.5 is required, and a boost-BED of 15-19 Gy_3.5 is considered adequate. Longer boost RT schedules with a BED value of higher than 20 Gy_3.5 do not offer additional benefits and might result in a higher risk for long-term post-radiation effects and waste of resources.