A New hybrid radiotherapy technique for non-small cell lung cancer: Is more effective for functional lung sparing

Background: The Conventional thoracic radiotherapy planning ignores regional pulmonary function changes. This study aimed to evaluate the beneficial effect of a new hybrid three-dimensional conformal radiation therapy (3DCRT)/intensitymodulated radiation therapy (IMRT) technique. Materials and Methods: Thirty patients with non-small cell lung cancer were included in this study. Four protocols were designed for each patient: anatomical IMRT (A-IMRT, based on the total lung), functional IMRT (F-IMRT), pure IMRT (O-IMRT) plan, and hybrid 3DCRT/IMRT plan (H3DCRT/IMRT), which were based on the functional lung. The opposing pair of fields in the O-IMRT and H-3DCRT/IMRT protocols provide 2/9 and 1/2 of radiation dose, respectively. The planning target volume coverage, dose in both total and functional lungs, maximum spinal cord dose, mean esophagus dose, mean heart dose, homogeneity index (HI), conformity index (CI), and treatment monitor units (MUs) were compared in this study. Results: The V5, V20, and mean dose (Dmean) of the both total and functional lungs in the H-3DCRT/IMRT protocol were the lowest among the four treatment regimes. For D2, D98, HI, and CI, the A-IMRT protocol was superior to the H-3DCRT/IMRT protocol. Compared with the A-IMRT protocol, the F-IMRT protocol achieved significantly lower V5, V20, and Dmean for functional lungs, but showed worse HI, CI, and maximum dose of spinal cord. The H-3DCRT/IMAT protocol significantly reduced the maximum spinal cord dose and MUs. Conclusions: The H-3DCRT/IMAT plan based on functional lung images appeared to be better than conventional F-IMRT in preserving functional lung without compromising on HI and CI in NSCLC patients.