Integrated Analysis of Dosimetric Quality and Planning Efficiency in Pelvic Radiotherapy: VMAT Versus 3D Conformal Techniques

Abstract

Background: Radiotherapy for pelvic malignancy demands precise targeting of the tumor with minimal dose delivery to the adjacent organs. Among alternatives, VMAT and 3DCRT differ considerably in delivery mechanics and in sculpting dose capacity. Published work providing intra-patient matched dosimetric comparisons on a single platform is scarce.
Objective: To objectively compare target coverage and sparing of organ-at-risk (OAR) between VMAT and 3DCRT in radiotherapy for pelvic cancer based on standardized planning and analysis techniques.
Methods: Fourteen male pelvic malignancy patients were retrospectively analyzed. VMAT and 3DCRT plans were designed for each patient with the Monaco Treatment Planning System. Planning target volume (PTV) parameters—coverage (%), homogeneity index (HI), conformity index (CI)—and OAR dose-volume parameters (bowel Vcc, rectum V30, kidney Dmean, spinal cord Dmax) were compared with paired t-tests (significance: p < 0.05).
Results: VMAT enhanced PTV coverage significantly better (99.31 ± 0.46% vs. 96.74 ± 0.99%; p < 0.01), reduced HI (0.17 ± 0.02 vs. 0.35 ± 0.01; p < 0.01), and improved CI (0.95 ± 0.10 vs. 0.53 ± 0.05; p < 0.01) than 3DCRT. VMAT reduced the mean doses to right kidney (p < 0.01), left kidney (p = 0.02), rectum V30 (p < 0.01), bowel Vcc (p < 0.01) and spinal cord Dmax (p=0.01).
Conclusion: Intra-patient matched comparison confirms VMAT's dosimetric benefit over 3DCRT in pelvic radiotherapy in terms of better target conformity and critical organ sparing. The results confirm the application of VMAT as the preferred planning modality in anatomically complex pelvic cancer cases.