gms | German Medical Science

Objective: To improve the effectiveness of boron neutron capture therapy (BNCT) for malignant brain tumors, we utilized epithermal rather than thermal neutrons for deep penetration, and we used two boron compounds, sodium borocaptate (BSH) and boronophenylalanine (BPA), with different accumulation mechanisms to increase the boron level in tumors while compensating for each other’s faults.

Methods: We have treated 38 malignant brain tumors, including 34 malignant gliomas and 4 malignant meningiomas, by modified BNCT since 2002. In this study, we analyzed the initial 13 patients, ten glioblastoma, one gliosarcoma, one anaplastic astrocytoma, and one anaplastic oligoastrocytoma, treated with BNCT from January 2002 to December 2003. Only one glioblastoma patient had no postoperative enhanced lesion.

The patients received ¹⁸F-BPA positron emission tomography, if available, to assess the accumulation and distribution of BPA before neutron irradiation. The neutron fluence rate was estimated by SERA (Simulation Environments for Radiotherapy Applications dose planning software) before irradiation. The patients received volumetric assessments, by MRI or CT scanning. Improvements in the images were assessed at 2 to 7 days after irradiation as initial effects, and their maximum effects on serial radiographic images were also analyzed.

Results: The mean initial tumor volume prior to BNCT was 42.3 cm³. Irrespective of that volume, in every patient who had an assessable lesion, the improvements on MRI/CT images were recognized both on initial assessments (volume reduction rate: 17.4% to 71.0%, mean 46.4%) and on follow-up assessments (30.3% to 87.6%, mean 58.5%). More than 50% of the contrast-enhanced lesions disappeared in 8 out of the 12 patients during the follow-up period. Mean survival time after diagnosis of all glioblastoma cases treated in this period was 23.4 months. Two patients are still alive. All malignant meningioma (WHO grade 3) cases treated with BNCT also showed good radiographic responses without aggravation.

Conclusions: This modified BNCT led to an improvement in the malignant gliomas both in respect toradiographic images and to longevities and is considered to be a promising therapeutic strategy, even for malignant meningiomas.