Treatment of medulloblastoma: comparison between volumetric modulated arc therapy and three-dimensional conformal radiation therapy

Abstract

Objective: To present the feasibility of the treatment of medulloblastoma with volumetric-modulated arc therapy (VMAT) planned with RayStation for Elekta linacs and compare the results with conventional treatment.

Materials and methods: 3 adult patients in prone position treated with 3D-conformal radiotherapy (3DCRT) with 6 MV and 18 MV were replanned with 6 MV VMAT. The dose prescription was 1.8 Gy/fraction. The evaluation of the techniques was carried out with dose-volume histograms and isodoses in target volumes and healthy tissues, and with conformity (CI) and homogeneity (HI) indexes.

Results: VMAT CI (0.79 ± 0.02) and HI (0.08 ± 0.02) of the tended to be better than those of 3DCRT (CI = 0.58 ± 0.03 and HI = 0.14 ± 0.07). For healthy tissues, a decrease in the maximum absorbed dose was observed (VMAT: D1% = 1.76 ± 0.04 Gy/fraction and 3DCRT: D1% = 1.93 ± 0.04 Gy/fraction) as well as in the overdoses (VMAT: V107% = 0.05 ± 0.08% and 3DCRT: V107% = 1.0 ± 0.5%). The dosimetric results of organs at risk showed no trend when both techniques were compared.

Conclusion: The performance with RayStation of the medulloblastoma treatment by VMAT is viable for Elekta linacs, and a greater coverage, homogeneity and conformation in the target is achieved. Overdoses were also markedly reduced compared with those caused by 3DCRT treatments.