# Fractionating Boost Dose in Postoperative Breast Radiotherapy

## TL;DR

This paper suggests optimal radiation boost doses after breast cancer surgery to reduce recurrence without unnecessary side effects.

## Contribution

The study proposes a biologically effective dose range for boost radiotherapy based on clinical trial data.

## Key findings

- A whole-breast irradiation BED of 65-75 Gy3.5 is required for effective treatment.
- A boost-BED of 15-19 Gy3.5 is adequate to reduce local recurrence risk.
- Higher boost-BED values do not improve outcomes and may increase side effects.

## Abstract

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 Gy3.5 is required, and a boost-BED of 15-19 Gy3.5 is considered adequate. Longer boost RT schedules with a BED value of higher than 20 Gy3.5 do not offer additional benefits and might result in a higher risk for long-term post-radiation effects and waste of resources.