Proton beam radiotherapy as part of comprehensive regional nodal irradiation for locally advanced breast cancer.

Purpose: This study evaluates acute toxicity outcomes in breast cancer patients treated with adjuvant proton beam therapy (PBT).

Methods: From 2011 to 2016, 91 patients (93 cancers) were treated with adjuvant PBT targeting the intact breast/chest wall and comprehensive regional nodes including the axilla, supraclavicular fossa, and internal mammary lymph nodes. Toxicity was recorded weekly during treatment, one month following treatment, and then every 6months according to the Common Terminology Criteria for Adverse Events (CTCAE) v4.