2699 - Re-Irradiation Toxicity and Survival Outcomes for Locoregionally Recurrent or New Ipsilateral Breast Cancer

Monday, September 30, 2024

3:00 PM – 4:00 PM ET

Location: Hall C

Screen: 20

Presenter(s)

Kamaria Lee, MD, AB

MD Anderson Cancer Center
Houston, TX

K. L. Lee¹, K. Stein¹, D. Swanson¹, K. L. Corrigan¹, S. M. Buszek², C. R. Goodman¹, K. E. Hoffman¹, M. P. Mitchell¹, K. T. Nead¹, G. H. Perkins¹, B. D. Smith¹, M. C. Stauder¹, E. A. Strom¹, W. A. Woodward¹, and S. F. Shaitelman¹; ¹The University of Texas MD Anderson Cancer Center, Houston, TX, ²Community Health Network, Indianapolis, IN

Purpose/Objective(s): For breast cancer patients (BC pts) who develop recurrent locoregional disease or a new ipsilateral primary, the safety of re-irradiation (re-RT) is an important clinical consideration. We hypothesize that re-RT may be done safely without significant acute or late toxicities. Materials/

Methods: We retrospectively identified BC p</span>ts at our institution who received re-RT from 2016-2022. Demographic and clinical data were obtained through medical record review. Descriptive statistics were calculated. 2- and 5-year overall survival were assessed using the Kaplan-Meier method.
Results: 92 pts were identified. Median toxicity follow-up was 25.1 months. Most (98%) had one course of re-RT; median time between initial RT and first re-RT was 9 [5-17] years. Re-RT was usually curative in intent (91%), with over half (55%) to breast/chest wall and nodes, 16 (19%) partial breast, 11 (13%) breast/chest wall alone, and 9 (11%) nodes alone. Most re-RT was with mixed photons/electrons 42 (45%) vs photons, protons, or electrons alone (35%, 12%, and 5%, respectively). Re-RT technique included 2D/3D for 66 courses (71%); advanced techniques (IMRT, IMPT, and VMAT) were utilized in 34 (37%). Median total dose for initial RT was 60 Gy for photons/electrons; only one patient had initial RT with protons (34 GyRBE). Most (67%) received at least 50 Gy for first re-RT. Most common re-RT acute toxicities were dermatitis (76; 82%), fatigue (58; 62%), and hyperpigmentation (52; 56%). 4 pts (4%) had grade 3+ acute toxicities. Late toxicities (>3 months) most often included fibrosis (47; 52%), lymphedema (29; 32%), and hyperpigmentation (28; 31%). 21 pts (23%) had grade 3+ late toxicities; the majority of which (76%) were fibrosis or atrophy/asymmetry. The most clinically severe grade 3 late toxicities included (both n=1): a tension pneumothorax secondary to rib fractures and severe subclavian artery stenosis with associated cyanosis and brachial plexopathy from extensive fibrosis. One pt experienced a possible grade 4 toxicity: extensive pulmonary fibrosis contributing to ICU hospitalization. 2-year overall survival was 91% and 5-year overall survival was 77%.
Conclusion: Re-RT can be a safe option for BC pts, with acceptable acute and late toxicities for most of our cohort. A majority were alive five years after re-RT. Additional follow-up for long-term toxicities is warranted and adequate p</span>atient education about potential risks is of great importance. Continued work is needed to understand the most appropriate re-RT candidates and radiotherapy techniques to optimize the therapeutic ratio. P</span>rospective analysis following published guidelines has begun, which will allow for long-term follow-up to better evaluate late toxicity outcomes.