Comparison study between different treatment planning techniques for medulloblastoma in terms of dosimetry,...

To compare three-dimensional conformal radiation therapy (3DCRT), intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) for medulloblastoma patients by evaluating dosimetry, radiobiology, and secondary cancer risk parameters.

Data from the Roshana Radiotherapy Center (Tehran, Iran) and the Ayatollah Khansari Hospital (Arak, Iran) were used to develop treatment plans using 3DCRT, IMRT, and VMAT for ten patients with medulloblastoma cancer. Using the Monaco® treatment planning system, all plans were created for an ELEKTA Versa HD linear accelerator with a 6 MV photon beam. For the planning target volume (PTV), dosimetric parameters (Dmin, Dmax, and Dmean), conformity index (CI), homogeneity index (HI), and tumor control probability (TCP) were assessed. For organs at risk (OARs) and normal structures, the normal tissue complication probability (NTCP), excess absolute risk (EAR), and lifetime attributable risk (LAR) were calculated.

The greatest PTV coverage was attained by VMAT, closely trailed by IMRT, both of which were considerably superior to 3DCRT. Compared to 3DCRT, VMAT and IMRT had substantially improved CI and HI values. Similar trends were seen in the TCP values. Unexpectedly, IMRT showed better OAR sparing for many structures, especially in the thoracic area. In the head and neck region, VMAT demonstrated superior sparing for smaller structures.

For the treatment of medulloblastoma, VMAT, and IMRT are generally better than 3DCRT because they offer better target coverage, conformance, and homogeneity. However, for many structures, IMRT showed unexpected superiority in OAR sparing.