Boron neutron capture therapy for malignant tumors related to meningiomas

Malignant meningiomas, similar to glioblastomas, are difficult tumors to control. We tried to control malignant tumors related to meningiomas by boron neutron capture therapy (BNCT).

Since June 2005, we applied BNCT with 13 rounds of neutron irradiation to seven cases of malignant tumors related to meningiomas. Three were anaplastic meningiomas, two were papillary meningiomas, one was an atypical meningioma, and one was a sarcoma transformed from a meningioma with cervical lymph node metastasis. All patients had previously undergone repetitive surgeries and radiotherapy. Follow-up images were available for six patients with an observation period between 7 and 13 months. We applied 18F-boronophenylalanine (BPA)-positron emission tomography (PET) before BNCT in six of the seven patients. One patient underwent methionine-PET instead of 18F-BPA-PET.

Five of the six patients who underwent BPA-PET analysis showed good BPA uptake, with a greater than 2.7 tumor-to-healthy brain ratio. The atypical meningioma case showed a tumor-to-healthy brain ratio of 2.0. The original tumor sizes were between 13.6 and 109 ml. Two of the three anaplastic meningiomas showed a complete response, and all six patients available for follow-up imaging showed radiographic improvements. Clinical symptoms before BNCT, such as hemiparesis and facial pain, were improved after BNCT in all but one patient. In this patient, a huge atypical meningioma arose from the falcotentorial junction and extended to the bilateral occipital lobes and brainstem; visual problems worsened after repetitive BNCT, with an increase in peritumoral edema.

Malignant meningiomas seem to be good candidates for BNCT.