2845 - Radiotherapy Patterns of Care and Toxicities after Breast Conserving Surgery with or without Immediate Reconstruction for Early-Stage Breast Cancer
Presenter(s)
S. Ramesh1,2, A. J. Khan3, C. Stern4, Q. LaPlant3, J. J. Cuaron3, D. A. Roth O’Brien3, M. B. Bernstein3, B. McCormick3, L. Z. Braunstein3, S. N. Powell3, and I. J. Choi3; 1Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, 2Medical College of Wisconsin, Milwaukee, WI, 3Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 4Plastic Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY
Purpose/Objective(s): Breast-conserving surgery (BCS) and radiotherapy (RT) remain standard components of breast conservation therapy (BCT) for early-stage breast cancer. Oncoplastic techniques at the time of BCS may optimize cosmesis, but the impact on RT delivery patterns and adverse events (AEs) is not well-characterized. We hypothesize that BCS with immediate reconstruction (BCS+Recon) compared with BCS alone (BCS) results in increased acute and late treatment-related AEs.
Materials/Methods: Patients with early-stage breast cancer treated with RT and BCS+Recon from 2/2020-5/2024 were identified from an institutional database and matched 1:1 based on age (<50, 50-70, >70), pathologic TNM stage, and receptor status with patients receiving RT and BCS. Clinicopathologic features, RT details, and acute (<90 days after RT completion) and late AEs were derived from the electronic medical record. AE rates between the groups were compared using Pearson’s chi-squared and Fisher's exact test for categorical outcomes. Subgroup analyses were conducted based on boost status (boost vs. no boost). Significance was defined as a two-sided p-value <0.05. Statistical analyses were performed using Python (v. 3.12) with SciPy statistical package (v. 1.17.0).
Results: In total, 213 BCS+Recon patients met criteria and were matched to 213 BCS patients. Dosimetric parameters including lumpectomy cavity volume, PTV boost volume, breast:cavity ratio, and breast:PTV boost ratio were all well-matched (p>0.05). Median follow-up was 25 months (36.5 BCS, 21 BCS+Recon). BCS+Recon patients were more likely to have boost omission despite intent to deliver (0% BCS vs. 15.6% BCS+Recon; p<0.001). The rate of acute grade (G)=2 AEs was higher in BCS+Recon patients (16.4% vs. 28.6%; p=0.004). The BCS+Recon group was more likely to experience G=2 acute dermatitis (13.1% vs. 22.5%; p=0.016). Acute breast pain was more common in the whole BCS+Recon group (14.1% vs. 34.7%; p<0.001) and in both boost (15.7% vs. 33.1%; p<0.001) and no boost (11.0% vs. 38.7%; p<0.001) subgroups. BCS+Recon patients not receiving a boost also experienced more acute breast edema (21.9% vs. 41.9%; p=0.012). Late arm lymphedema was more common with BCS+Recon (2.3% vs. 6.6%; p<0.035), along with late fibrosis overall (26.8% vs. 45.5%; p<0.001), as well as fibrosis in boost (30.7% vs. 49.0%; p=0.0015) and no boost (19.2% vs. 37.1%; p=0.020) subgroups.
Conclusion: Patients with early-stage breast cancer undergoing RT with BCS+Recon were more likely to develop acute and late AEs compared with BCS alone. BCS+Recon also impacted planned boost delivery, predominantly due to tissue rearrangement and challenges reliably delineating a surgical bed. Correlation of AEs with DVH metrics and rigorous evaluation of long-term breast cosmesis will provide further clarity on the impact of immediate reconstruction in patients pursuing BCT.