2880 - Longitudinal Dynamics and Recovery of Lymphocytes In Patients with Breast Cancer Receiving Radiotherapy without Chemotherapy after Breast-Conserving Surgery: A Second Analysis of a Phase III Randomized Trial
Presenter(s)
Y. Song1, Z. Qiu1, G. Sun2, X. Zhao1, S. Chen3, H. Jing1, H. Fang1, Y. Tang2, Y. Song1, J. Jin4, Y. Liu1, B. Chen5, Y. Tang6, S. Qi2, N. Lu1, N. Li7, Y. Zhai8, W. Zhang7, X. Liu1, Z. Yang1, Y. LI6, 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, 2State Key Laboratory of Molecular Oncology and Department 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, 3Department of Radiation Oncology, National Cancer Center/ National Clinical Research Center for Cancer/ Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Bejing, China, 4Department of Radiation Oncology,National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital,Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, China, 5Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, Beijing, China, 6State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 7State Key Laboratory of Molecular Oncology and Department 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, 8Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
Purpose/Objective(s): To date, no study has yet reported on the time period that peripheral lymphocyte counts (PLCs) take to recover to the true baseline level after radiotherapy (RT). This study aims to assess the longitudinal dynamics of PLCs in patients with breast cancer treated with RT without chemotherapy after BCS and to determine the timepoint at which PLCs recover to the baseline levels.
Materials/Methods: This second analysis was performed using the data of 203 patients from XXXX trial, a phase III, randomized controlled trial comparing hypofractionated RT (HFRT) with conventional fractionated RT (CFRT) after BCS. PLCs were obtained at baseline (before treatment), pre-RT, weekly during RT, and regularly after RT until the 5-year follow-up. Generalized linear mixed models were used for the longitudinal analyses of PLCs over time.
Results: The pre-RT PLCs were similar to the baseline, and the PLCs gradually decreased during RT. In the HFRT and CFRT groups, the PLCs recovered to the baseline level 3 and 4 years after RT, respectively. Compared with the CFRT group, the HFRT group had a significantly higher mean nadir PLC (1.26 ± 0.42 × 109/L vs. 1.05 ± 0.32 × 109/L, P < 0.001) and a significantly lower =G2 lymphopenia rate (6.5% vs. 24.5%, P = 0.001).
Conclusion: This study reports the timepoint at which the decreased PLCs recover to the baseline levels, with the longest lymphocyte observation period so far (5 years after RT). Our results revealed that RT-induced lymphopenia (RIL) in patients with breast cancer undergoing BCS without chemotherapy was generally mild. HFRT induced less severe lymphopenia compared with that induced by CFRT. However, the PLCs experienced a prolonged reduction period in both groups, recovering to baseline level 3 years after RT with HFRT and 4 years with CFRT. These findings provide additional evidence supporting the clinical use of HFRT and highlight the need for further investigation on how to protect PLCs from reduction or facilitate their recovery after RT.