Patients and Methods: Men who received PT for localized
breast cancer between 2012 and 2022 were identified from a prospective database. Toxicities were prospectively recorded by using the Common Terminology Criteria for Adverse Events (CTCAE), version 4.0.
Results: Five male patients were identified. All had
estrogen receptor (ER)-positive, Her2neu-negative disease and received adjuvant endocrine
therapy. One had genetic testing positive for BRCA2, one had a variant of unknown significance (VUS) in the APC gene, and one had a VUS in MSH2. Median age was 73 years (range, 41-80). Baseline comorbidities included
obesity (n = 1), diabetes (n = 1),
hypertension (n = 4), history of
deep vein thrombosis (n = 1), personal history of
myocardial infarction (n = 3; 1 with a pacemaker), and a history of
lung cancer (n = 1). All received PT to the left chest wall and comprehensive regional lymphatics. One received passive-scattering PT, and 4 received pencil beam scanning. One patient received a boost to the
mastectomy incision via electrons. Median heart dose was 1 GyRBE (range, 0-1.0), median 0.1-cm3 dose to the left anterior descending artery was 7.5 GyRBE (range, 0-14.2), and median follow-up was 2 years (range, 0.75-6.5); no patient experienced a new
cardiac event, and all remain free from
breast cancer recurrence and progression.
Conclusion: In a small case series for a rare diagnosis, PT to the chest wall and regional lymphatics, including internal mammary nodes, resulted in low cardiac exposure, high local regional disease control rates, and minimal toxicity.
Proton therapy should be considered for treating men with
breast cancer to achieve cardiac sparing.