The purpose of this guideline is to offer recommendations on fractionation for whole breast irradiation (WBI) with or without a tumor bed boost and guidance on treatment planning and delivery.

The American Society for Radiation Oncology (ASTRO) convened a task force to address 5 key questions focused on dose-fractionation for WBI, indications and dose-fractionation for tumor bed boost, and treatment planning techniques for WBI and tumor bed boost. Guideline recommendations were based on a systematic literature review and created using a predefined consensus-building methodology supported by ASTRO-approved tools for grading evidence quality and recommendation strength.

For women with invasive breast cancer receiving WBI with or without inclusion of the low axilla, the preferred dose-fractionation scheme is hypofractionated WBI to a dose of 4000 cGy in 15 fractions or 4250 cGy in 16 fractions. The guideline discusses factors that might or should affect fractionation decisions. Use of boost should be based on shared decision-making that considers patient, tumor, and treatment factors, and the task force delineates specific subgroups in which it recommends or suggests use or omission of boost, along with dose recommendations. When planning, the volume of breast tissue receiving >105% of the prescription dose should be minimized and the tumor bed contoured with a goal of coverage with at least 95% of the prescription dose. Dose to the heart, contralateral breast, lung, and other normal tissues should be minimized.

WBI represents a significant portion of radiation oncology practice, and these recommendations are intended to offer the groundwork for defining evidence-based practice for this common and important modality. This guideline also seeks to promote appropriately individualized, shared decision-making regarding WBI between physicians and patients.