Physics and Imaging in Radiation Oncology | 2019
Functional perfusion image guided radiation treatment planning for locally advanced lung cancer
Abstract
Background and purpose Functional avoidance radiation therapy (RT) aims at sparing functional lung regions. The purpose of this simulation study was to evaluate the feasibility of functional lung avoidance methodology in RT of lung cancer and to characterize the achievable dosimetry of single photon emission computed tomography (SPECT) guided treatment planning. Materials and methods Fifteen consecutive lung cancer patients were included and planned for definitive RT of 60–66\u202fGy in 2-Gy fractions. Two plans were optimized: a standard CT-plan, and functional SPECT-plan. The objective was to reduce dose to the highly functional lung subvolumes without compromising tumour coverage, and respecting dose to other organs at risk. For each patient a 3D-conformal, intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy plans were created for standard and functional avoidance. Standard versus functional dose-volume parameters for functional lung (FL) subvolumes, organs at risk and tumour coverage were compared. Results The largest dose reduction was achieved with IMRT plans. Functional plans resulted in dose reduction from 9.0\u202fGy to 6.7\u202fGy (mean reduction of 2.3\u202fGy or 26%) to the highest functional subvolume FL80% (95%CI 1.1; 3.5). Dose to FL40% was reduced from 13.3\u202fGy to 11.6\u202fGy with functional planning. Dose reduction to FL40% was 1.7\u202fGy (95%CI 0.9; 2.6). Functional volume of lung receiving over 20\u202fGy improved by 5% (standard 22%, functional 17%). Dose to organs at risk and tumour coverage were not significantly different between plans. Conclusions SPECT/CT-guided planning resulted in improved dose-volumetric outcomes for functional lung. This methodology may lead to potential reduction in radiation-induced lung toxicity.