Lymphopenia in glioblastoma and its association with brain vessel irradiation: pilot retrospective evaluation of dose-volume parameters

Radiotherapy (RT) plays a central role in the management of glioblastoma, often in combination with other treatment modalities. While RT can enhance both local and systemic tumor control, especially when used alongside immunotherapy, it is also associated with lymphopenia - a reduction in lymphocyte count - which has been linked to poorer treatment outcomes and reduced survival. This retrospective study aimed to examine the relationship between radiation dose delivered to brain vessels and the severity of lymphopenia in patients with newly diagnosed glioblastoma treated at a tertiary cancer center in 2021. Brain vessels were manually contoured using MRI data, and dose-volume analysis was conducted. Lymphopenia severity was graded according to CTCAE v5.0, and statistical analyses were performed to identify any correlations. Among the 28 patients analyzed, 32% developed grade 1-3 lymphopenia. No significant correlation was found between the radiation dose to brain vessels and the degree of lymphopenia. The median volume of irradiated vessels did not differ significantly between patients with and without lymphopenia. In glioblastoma patients, multiple factors contribute to decreased lymphocyte count - e.g., chemotherapy and corticosteroid use. Although no definitive link was identified, the study underscores the importance of preserving lymphocyte counts during glioblastoma treatment and supports the need for further prospective research to explore strategies like lymphocyte-sparing RT and to better understand the mechanisms behind treatment-related lymphopenia.