Speaker
Description
BNCT for large-volume oral cavity cancer challenges the balance between maximizing tumour dose and protecting organs at risk. Single-field irradiation often fails to achieve deep-dose coverage due to entry angle constraints. This study evaluates the dosimetric impact of single-field versus two-field configurations. A retrospective analysis was performed for oral cavity cancer (GTV 96.46 cc) treated at the Tsing Hua Open-pool Reactor using NTHUplan. Plan A (two-field) employed a 10 cm aperture collimator combining F1 (right-lateral, head tilted 10° right) and F2 (anterior, head rotated 25° left). Plan B (single-field) used a 14 cm aperture collimator with a single anterior beam (head rotated 30° left). Blood boron concentration was fixed at 30 ppm. Dose constraints included tumour Dmin >20 Gy-w and mucosa Dmax <15 Gy-w. Plan A achieved tumour Dmax/Dmean of 30.31/22.13 Gy-w, superior to that of Plan B (28.26/19.24 Gy-w), representing improvements of 15.0% in mean dose and 7.3% in maximum dose. Although Plan A required a longer irradiation time (28.92 vs. 17.97 min, +61%), oral mucosa Dmax was maintained at the constraint limit (15 Gy-w) in both plans. Right parotid Dmax increased in Plan A (7.46 vs. 4.49 Gy-w) but remained within tolerance (<8 Gy-w). Clinical treatment using Plan A (at 33.69 ppm) confirmed planning predictions. For large-volume oral cavity cancer, two-field BNCT significantly improves tumour coverage (+15%) while strictly adhering to mucosa constraints. The increased irradiation time and parotid dose remain clinically acceptable, supporting the two-field configuration as a viable strategy for complex tumour geometries.