Beams Arrangement in Non-Small Cell Lung Cancer (NSCLC) According to PTV and Dosimetric Parameters Predictive of Pneumonitis

The aim of this study is to propose and validate an original new class of solutions for three-dimensional conformal radiation therapy (3DCRT) treatment planning for non-small cell lung cancer (NSCLC) according to the different patterns of disease presentation (on the basis of tumor location and volume) and to explore beams arrangement (planar or no-planar solutions) to respect dose constraints to the lung parenchyma. Benchmarks matched to validate the new approach are interuser reproducibility and saving on planning time. Tumor location was explored and specific categories created according to the tumor volume and location. Therefore, by applying planar and no-planar 3D plans, we searched for an optimization of the beams arrangement for each category. Dose-volume histograms (DVHs) were analyzed and a plan comparison performed. Results were then validated (class solution planning confirmation) by applying the same strategy to another group of patients. This has been realized at two dose levels (50.4 and 59.4 Gy). Fifty-nine patients were enrolled in this dosimetric study. In the first 27 patients ("exploratory sample") three main planning target volume location categories were identified according to the pattern of the disease presentation: (1) centrally located; (2) peripheral T and mediastinal N (P+N); and (3) superior sulcus. Original class solutions were proposed for each location category. On the next 32 patients ("validation sample"), the treatment planning started directly with the recommended approach. Mean V_20Gy value was 18.8% (SD ± 7.25); mean V_30Gy:12% (SD ± 4.05); and mean lung dose: 11.6Gy (SD ± 5.77). No differences between the two total dose level groups were observed. These results suggest a simple and reproducible tool for treatment planning in NSCLC, allowing interuser reproducibility and cutting down on planning time.