Is VMAT Planning Feasible in Pediatric Neuroblastoma?

Aim: To do a dosimetric comparison between VMAT (Volumetric modulated arc radiotherapy) and 3DCRT (3-dimensional conformal radiotherapy) plans in pediatric abdominal neuroblastoma. Methods: 15 patients with high risk abdominal neuroblastoma, treated between January 2012 and December 2015, with 3DCRT were reviewed. For comparison purpose, VMAT plans were also made on the planning CT scans. Volumetric and dosimetric changes in target volumes and normal structures were analyzed. Results: VMAT plans covered target volumes more conformally than 3D-CRT (Conformity index: 1.12 vs 1.88; p=0.028). The former was also superior to 3 DCRT plans in terms of lesser Dmean and V18 doses to ipsilateral kidney (Dmean: 15.45 Gy vs 18.27 Gy; p=0.02 and V18: 41.45 % vs 60.65 %; p=0.004), and contra lateral kidney (Dmean: 9.86 Gy vs 14.13 Gy; p= 0.005 and V18: 10.18 vs 34.39; p=0.002), V12 and V15 parameters of liver (V12: 24.10 % vs 31.89 %; p= 0.000 and V15: 14.03 % vs 24.99 %; p=0.001) and Dmax spine (17.42 Gy vs 23.40 Gy; p = 0.000). The homogeneity index of VMAT plans was 0.01 compared to 0.87 with 3DCRT (p = 0.02) Monitor units used to deliver radiation were 356 with VMAT compared to 246 only with 3DCRT (p = 0.035). Time to deliver a single fraction with VMAT and 3D-CRT was 1.65 and 2.78 min, respectively (p=0.048). The integral doses (Dmean) to non target tissues were however not significantly different between the two plans [4.97 Gy (VMAT) vs 4.07 Gy (3DCRT); p =0.20]. Conclusion: The study demonstrates the superiority of VMAT plans over 3DCRT plans in terms of doses to organs at risk. The integral doses were also not significantly increased with VMAT planning, making these plans feasible to be used in pediatrics abdominal neuroblastoma.