AUTHOR=Laughlin Brady S. , Bhangoo Ronik S. , Niska Joshua R. , Thorpe Cameron S. , Girardo Marlene E. , Anderson Justin D. , Kosiorek Heidi E. , McGee Lisa A. , Hartsell William F. , Chang John H. , Rossi Carl J. , Tsai Henry K. , Choi Isabelle J. , Vargas Carlos E. 

TITLE=Proton therapy for isolated local regional recurrence of breast cancer after mastectomy alone

JOURNAL=Frontiers in Oncology

VOLUME=Volume 12 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2022.925078

DOI=10.3389/fonc.2022.925078

ISSN=2234-943X

ABSTRACT=Abstract
Purpose/Objectives:  To assess adverse events (AEs) and disease-specific outcomes after proton therapy for isolated local regional recurrence (LRR) of breast cancer after mastectomy without prior radiotherapy (RT).
Materials/Methods:  Patients were identified from a multi-institutional prospective registry and included if diagnosed with invasive breast cancer, initially underwent mastectomy without adjuvant RT, experienced an LRR, and subsequently underwent salvage treatment including proton therapy.  Follow-up and cancer outcomes were measured from date of RT completion. 	
Results:  Nineteen patients were included. Seventeen patients were treated with proton therapy to the chest wall and comprehensive regional lymphatics (17/19, 90%). Maximum grade AE was grade 2 in 13 (69%) patients and grade 3 in 4 (21%) patients.  All patients with grade 3 AE received > 60 GyE (p=0.04, Spearman correlation coefficient=0.5). At last follow-up, 90% of patients were alive with no LRR or distant recurrence.
Conclusions:  For breast cancer patients with isolated LRR after initial mastectomy without adjuvant RT, proton therapy is well-tolerated in the salvage setting with excellent local regional control.  All grade 3 AEs occurred in patients receiving > 60 GyE.