A treatment planning study on glioblastoma with different techniques using boron neutron capture therapy, 3-dimensional conformal radiotherapy, and intensity modulated radiotherapy

To propose adequate indices predicting efficacy of boron neutron capture therapy (BNCT) for glioblastoma, a comparative treatment planning study between BNCT, 3-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT) was performed, and dose–volume histograms (DVHs) on planning target volume (PTV) and normal brain were calculated. Therapeutic benefit of BNCT was quantitatively evaluated using conformity indices, which have been previously suggested by radiation therapy oncology group (RTOG) and Saint-Anne, Lariboisière, Tenon (SALT). Although dose homogeneities from the BNCT plans were poor than the other modalities due to simple irradiation fields, lesion coverage factor, CVF, from the BNCT plans were comparable to those from the 3D-CRT and IMRT plans (median values, 0.991, 0.989, and 0.961, respectively). The geometrical factors, g, from the BNCT plans, which describes target volumes receiving doses under the prescribed doses and normal brain volume covered by the prescribed doses, were lowest compared to those for the other modalities (median values, 0.009, 0.115, and 0.043). For the BNCT plans, maximum dose escalation up to 2.080 times the prescribed dose was possible without exceeding normal brain tolerance dose. As the indices can evaluate the quantitative benefit of BNCT and maximum dose escalation for the individual patient, it is expected that the indices can effectively evaluate the treatment plan of BNCT.