2716 - Reconstruction Outcomes of Post-Mastectomy Radiotherapy with Proton Therapy: A Multi-Institutional Analysis
Presenter(s)
S. Choi1,2, D. J. Lee1, C. Padilla1, A. Desai3, M. A. Chakraborty4, S. S. Rhodes5, I. M. Reis6, J. R. Mella-Catinchi3, R. Shammas7, S. Azoury8, N. K. Taunk9, E. Berlin9, I. J. Choi10,11, and C. Takita1; 1Department of Radiation Oncology, University of Miami Sylvester Comprehensive Cancer Center, Miami, FL, 2Department of Radiation Oncology, University of Southern California Keck School of Medicine, Los Angeles, CA, 3Division of Plastic and Reconstructive Surgery, DeWitt Daughtry Family Department of Surgery, University of Miami, Miami, FL, 4Rutgers New Jersey Medical School, Newark, NJ, 5Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 6Department of Public Health Sciences and Sylvester Biostatistics/Bioinformatics Shared Resources (BBSR), University of Miami, Sylvester Comprehensive Cancer Center, Miami, FL, 7Department of Plastic and Reconstructive Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, 8Division of Plastic Surgery, Hospital of the University of Pennsylvania, Philadelphia, PA, 9Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 10New York Proton Center, New York, NY, 11Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY
Purpose/Objective(s):
Reconstruction outcomes for patients with breast cancer receiving mastectomy with immediate reconstruction in the setting of modern proton technology and planning techniques remain limited. The objective of this multi-institutional study was to evaluate reconstruction-related complications requiring surgical intervention among patients who received post-mastectomy proton radiation therapy (PMPRT) after immediate expander- or implant-based breast reconstruction (IBR).Materials/Methods:
Patients from three U.S. institutions who underwent IBR prior to PMPRT with pencil beam scanning between 2015-2023 were included. Patients with metastatic disease, prior chest wall irradiation, or autologous reconstruction were excluded. Reconstruction type at the time of radiation was limited to permanent implant (PI) or tissue expander (TE). A major reconstruction complication (MRC) was defined as any reconstruction-related event requiring surgical intervention. Absolute reconstruction failure (ARF) was defined as permanent loss of BR. Routine revision (RR) was defined as elective cosmetic or symmetry procedure. Kaplan-Meier analysis estimated freedom from MRC, and Cox regression was used to identify predictors of MRC.Results:
A total of 106 patients were identified, including 5 patients treated for bilateral disease. Median follow-up was 51.7 months, and median age was 40 years (range: 23-73). At the time of PMPRT, 34.9% of patients had PI (21.7% prepectoral, 13.2% postpectoral) and 65.1% had TE (40.6% prepectoral, 24.5% postpectoral). Radiation dose was 50.4 Gy in 28 fractions in 59.4% of patients, 50 Gy in 25 fractions in 37.7%, and 45 Gy in 25 fractions in 2.8%. Twenty patients (18.9%) received a boost. Overall, 14 patients (13.2%) developed MRC, including 4 (3.8%) who experienced ARF due to infection. Freedom from MRC at 2 years was 96.2%, at 4 years was 86.8%, and at 6 years was 83.9%. On univariable analysis evaluating age, reconstruction type and location, BMI, diabetes, smoking, race, ethnicity, systemic therapy, and boost, there were no significant predictors of freedom from MRC. Twenty-nine patients (27.3%) underwent a RR. Grade 3 capsular contracture occurred in 15 patients (14.2%) and Grade 4 occurred in 8 patients (7.5%).Conclusion:
In this multi-institutional cohort, approximately 13% of patients developed MRC following PMPRT, with ARF occurring in fewer than 4%. These findings suggest largely successful reconstruction outcomes in patients undergoing PMPRT with pencil beam scanning technology, with infection and contracture representing clinically significant complications. Prospective studies and direct proton vs. photon comparative analyses are warranted to further define the impact of modality selection on long-term reconstruction durability.