2687 - Complications of Implant-Based Reconstruction and Post-Mastectomy Radiation in the Era of Adjuvant CDK4/6 Inhibitors

H. Iqbal¹, B. Juneja¹, S. Ahlawat¹, S. Bonawitz², A. L. Fahey², S. Chryssofos², C. Loveland-Jones³, L. Steinmetz³, D. Markabawi⁴, C. Kurian⁴, and A. E. Dragun¹; ¹Department of Radiation Oncology, Cooper Medical School of Rowan University, MD Anderson Cancer Center at Cooper University Healthcare, Camden, NJ, ²Division of Plastic and Reconstructive Surgery, Cooper Medical School of Rowan University, Cooper University Healthcare, Camden, NJ, ³Division of Breast Surgery, Cooper Medical School of Rowan University, MD Anderson Cancer Center at Cooper University Healthcare, Camden, NJ, ⁴Division of Hematology and Oncology, Cooper Medical School of Rowan University, MD Anderson Cancer Center at Cooper University Healthcare, Camden, NJ

Purpose/Objective(s): Abemaciclib, a cyclin-dependent kinase 4/6 inhibitor, is approved for use in hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer. The toxicity profile of this agent is derived from studies favoring patients treated with breast conservation therapy. This study investigates the impact of abemaciclib on postoperative complications in the setting of post-mastectomy radiation therapy (PMRT) and TE/implant (TEI)-based reconstruction. Materials/

Methods: A single-center, retrospective chart review of a prospectively collected database was conducted. Patients who underwent mastectomy with PMRT and TEI breast reconstruction between 2020 and 2022, contemporaneous with introduction of abemaciclib in clinical use, were included. Data was collected for demographic information, tumor pathology, chemotherapy, radiation therapy, and reconstructive complications. Descriptive statistics were used to characterize the study population and determine rates of any complication, major complications requiring reoperation, and complication subtypes (contracture, extrusion, physical TEI changes, infection, seroma, dermatitis, pain). Chi-square and Fisher Exact tests were used to assess the association between abemaciclib use and complication rates as the primary endpoint. Secondary endpoints of associations between potential risk factors and complication rates were also assessed via such statistical testing.
Results: The study included 75 patients, 15 of whom (20.0%) underwent adjuvant abemaciclib therapy. The mean age was 48 years. 69.3% identified as White, 17.3% as Black/African American, and 13.3% as Hispanic. Among surgical risk factors, 34 patients (45.3%) were obese (BMI = 30), 24 (32.0%) had a smoking history, and 4 (5.3%) had diabetes. The incidences of any complication and major complications were 33.3% and 17.5%, respectively. There was no significant association between abemaciclib use and any complication (p = 1.000), major complications (p = 0.729), or any complication subtype (p = 0.865). There was no significant association between any complication and age (p = 0.203), smoking (p = 0.431), maximum radiation dose (p = 0.960), mastectomy type (p = 0.740), and prepectoral vs. subpectoral TE placement (p = 0.209). There was a significant association between BMI and any complication (p = 0.014).
Conclusion: The study suggests that use of adjuvant abemaciclib is not associated with an increased risk of post-radiation reconstructive complications in patients undergoing PMRT/TEI-based reconstruction. The overall incidence of complications and finding of BMI as a significant risk factor are consistent with reported literature on PMRT/TEI-based reconstruction. Continued surveillance of complications associated with abemaciclib is warranted with repeat analysis of a larger sample size.