Dosimetric Comparison between Flattening Filter Free Coplanar and Non-Coplanar Volumetric Modulated Arc Therapy for Lung Stereotactic Body Radiotherapy.

Abstract

The target of this study's project was to evaluate the variations between non-coplanar and coplanar volumetric modulated arc therapy for flattening filter-free stereotactic body radiotherapy in the lungs and determine which is more accurate in terms of dose delivery to the target tumor and preservation of surrounding normal tissues. Methods: Fifteen cases had non-small cell lung cancer tumors with varying positions and sizes that had been treated. For each case, two plans have been created: coplanar and non-coplanar volumetric modulated therapy using a two half arcs plan. Four-dimensional computed tomography had been performed on each case. The recommended dosage is 48 Gy divided into 4 sessions. Results: Regarding both plans, the mean of the conformality index and gradient index values for coplanar and non-coplanar VMAT plans, respectively, are 0.98 vs. 1.0 and 3.75 vs. 3.4, exhibiting a statistically significant variation (P = 0.001). Concerning organs at risk, there was a significant benefit to include non-coplanar arcs in preserving a healthy lung. The non-coplanar plan's average V20% values are 4.18 Gy, yet the coplanar plan are 4.49 Gy, exhibiting a statistically significant variation (P = 0.001). The average value of spinal cord volume <0.35 cc for the non-coplanar plan is 6.35 Gy compared to the coplanar plan, which is 7.21 Gy, and this is statistically significant (P = 0.017). Conclusions: In many cases, the non-coplanar method demonstrated greater target coverage and sparing of essential structures, especially for tumors with unusual shapes or those positioned adjacent to critical structures.