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 of HYPOfractionation in BREAST radiotherap
Yu-Chun Song, Chao-Nan Zhang, Guang-Yi Sun, Xu-Ran Zhao, Si-Ye Chen, Zi-Han Qiu, Hao Jing, Hui Fang, Yu Tang, Yong-Wen Song, Jing Jin, Yue-Ping Liu, Bo Chen, Yuan Tang, Shu-Nan Qi, Ning-Ning Lu, Ning Li, Yi-Rui Zhai, Wen-Wen Zhang, Xin Liu, Zhuan-Bo Yang, Ye-Xiong Li, Shu-Lian WangBackground
Radiotherapy-induced lymphopenia (RIL) has been associated with inferior clinical outcomes in multiple solid tumors. However, the long-term dynamics and recovery of peripheral lymphocyte counts (PLCs) after radiotherapy remain poorly characterized.
Objectives
To evaluate the longitudinal dynamics of PLCs in patients with breast cancer treated with radiotherapy (RT) without chemotherapy after breast-conserving surgery (BCS) and to identify the timepoint of recovery to pre-treatment levels.
Design
A secondary analysis of PLC dynamics was performed in selected patients enrolled in the prospective, multicenter, randomized phase III CHN-HYPOBREAST trial comparing hypofractionated RT (HFRT) with conventional fractionated RT (CFRT) after BCS.
Methods
This study included 203 patients. Among them, 96 were in the HFRT group and 107 were in the CFRT group. PLCs were measured at baseline (before any cancer treatment), pre-RT (after surgery but before RT), weekly during RT, and periodically up to 5 years after RT. Longitudinal PLC trends were analyzed using generalized linear mixed models.
Results
The pre-RT PLCs were comparable to 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 × 10
9
/L vs. 1.05 ± 0.32 × 10
9
/L,
Conclusions
RT-induced lymphopenia in patients with breast cancer undergoing BCS without chemotherapy was generally mild. HFRT resulted in less severe lymphopenia than 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 strategies to minimize RIL and promote lymphocyte recovery.