Lymphopenia associated with whole-brain radiotherapy and its effects on clinical outcomes of patients with brain metastases

There is increasing awareness of radiotherapy's potential side effects, such as lymphopenia. Therefore, this study aimed to establish the association between WBRT and the development of lymphopenia in patients with brain metastases undergoing brain radiotherapy (RT), along with evaluating the corresponding clinical outcomes. Including 116 patients with brain metastases undergoing brain radiotherapy, the study collected the absolute lymphocyte counts (ALC) within 2 weeks before brain radiotherapy (pre-radiotherapy, pre-RT), as well as ones at 1 and 2 months after completing RT (post-RT). Univariate and multivariate analyses were performed to identify associations between radiation modality and post-RT ALC. The relationships between post-RT ALC and overall survival were evaluated with Kaplan-Meier analysis and a multivariate Cox regression model. The median ALC definitely decreased at 1 month post-RT, but at 2 months post-RT, gradually rose but not to the pre-RT ALC. The multivariate analysis identified WBRT and lower pre-RT ALC as independent risk factors associated with the decrease in post-RT ALC at 1 month. It also revealed more than 4 brain metastases, G3-4 lymphopenia at 1 month and lower post-RT ALC at 2 months exhibited significantly worse prognosis regardless of the radiation modality. However, there was indeed an independent correlation between radiation modality and the outcome of intracranial progression-free survival (PFS). To approach the feasibility and reasonableness of treatment, clinicians should carefully consider various factors to achieve long-term survival of patients.