L. Xuan1, Y. Zhai1, B. Lan2, C. Zhu1, L. Zhou3, Y. Liu1, B. Chen1, H. Fang1, Y. Song1, N. Lu1, S. Qi1, H. Jing1, Y. Tang1, W. Zhang1, Y. LI1, F. Ma2, and S. Wang1; 1Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 2Department of Medical Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 3Department of Radiology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
Purpose/Objective(s): Abemaciclib plus hormone therapy has been the standard adjuvant treatment for high-risk hormone receptor (HR) positive, human epidermal growth factor receptor 2 (HER-2) negative breast cancer and radiotherapy was also recommended for these patients to achieve satisfied local control. Although in vitro studies exhibited favorable tumor cell reduction after concurrent abemaciclib and radiation, the unclear safety precluded the development of clinical trials. To investigate the safety and feasibility of concurrent abemaciclib and postoperative radiotherapy for breast cancer, we proposed this real-world analysis. Materials/
Methods: We searched for patients who fulfilled the following eligibility criteria, female aged 18-70 years old, pathologically diagnosed as breast cancer, with stage II-III, received breast conserving surgery or mastectomy followed by standard chemotherapy, received concurrent radiotherapy and abemaciclib in our institution between December 2021 to December 2022. Those who with breast sarcoma or incomplete medical records were excluded. Data regarding the clinicopathological characteristics, treatment details, adverse events (AEs) during radiation and within 12 months after the radiation were collected. AEs were reassessed according to National Cancer Institute common terminology criteria for adverse events, version 5.0. Results: From December,2021 to December,2022, 10 patients fulfilled the criteria and were analyzed in this study. The median age was 51.5 years old (ranged 36-58 years old). Seven patients (70%) were with disease of pathological or yp stage III. Neoadjuvant chemotherapy was administrated to 5 patients. Nine patients received chest wall irradiation and the other 1 patient received whole breast irradiation plus tumor bed boost. Regional lymph node irradiation, including superior clavicular and subclaviscular were delivered to all the ten patients. Four patients received internal mammary lymph node irradiation. All of the patients received volumetric modulated arc therapy. Conventional fractionation (2Gy per fraction) and hypofractionation radiotherapy (2.9Gy per fraction), was delivered to 2 and 8 patients. Abemaciclib was prescribed for 150mg twice daily. All of the patients finished the radiation without dose reduction or suspending. Abemaciclib dose reduction to 100mg twice daily was observed in 1 patient. No Grade 4-5 AE was not observed. Totally, Grade 3 AE were recorded in 1 patient, who was with Grade 3 leukopenia and recovered after treatment. Grade 2 interstitial pneumonia (both in radiation field and after radiation field) were recorded in 1 patient, who was diagnosed at 6 months after radiation (more likely attribute to abemaciclib) and recovered after intervention. The most common AE was diarrhea (Grade 1, 40% and Grade 2, 60%). Conclusion: Concurrent abemaciclib and postoperative radiotherapy is safe with tolerable and controllable toxicities. Prospective studies with large samples were warranted.
