The level of circulating M-MDSCs as an indicator for the therapeutic outcome of BNCT in end-stage malignant brain tumor patients.

Abstract

PurposeBoron neutron capture therapy (BNCT) is a promising treatment modality for patients diagnosed with malignant brain tumors. It is currently used for emergency and compassionate purposes to treat end-stage malignant glioma or recurrent head and neck cancer patients in Taiwan. Understanding the factors influencing treatment response is crucial for optimizing patient care. This study aimed to investigate the association between tumor response and various parameters in end-stage malignant glioma patients following BNCT. Patients and methodsFifteen patients with end-stage malignant brain tumors underwent a single fraction of BNCT. The treatment response was evaluated using cranial MRI, and the association between treatment response and BNCT parameters was analyzed. Additionally, circulating MDSC levels were measured by flow cytometry and correlated with patients’ survival. ResultsBNCT exhibited significant therapeutic efficacy in reducing tumor volume of these end-stage glioma patients, with three patients achieving complete response (CR) and ten patients achieving partial response (PR) within one month, resulting in an impressive objective response rate (ORR) of 80%. The median overall survival (OS) is 9 (1.77, 12.47) months, and the progression-free survival (PFS) is 1.34 (0.53, 9.53) months. Kaplan-Meier analysis showed that the patients with CR and PR displayed better survival than those with stable disease (SD). Treatment response was not significantly associated with initial tumor size, blood boron concentration, T/N ratio, or T/B ratio. The ROC curve revealed a cut-off value of 5% of circulating M-MDSCs with a sensitivity of 66.67% and specificity of 73.33%, respectively, for predicting the glioma patient’s response to BNCT. ConclusionsThis clinical study demonstrates that BNCT can reduce tumor burden, improve disease control, and prolong survival in end-stage glioma patients. Circulating M-MDSCs may serve as a predictive indicator for the treatment response of these patients following BNCT.