Comparison study between different treatment planning techniques for medulloblastoma in terms of dosimetry, radiobiology, and secondary cancer risk

Introduction: To compare three-dimensional conformal radiation therapy (۳DCRT), intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) for medulloblastoma patients by evaluating dosimetry, radiobiology, and secondary cancer risk parameters. Methods and Materials: Data from the Roshana Radiotherapy Center (Tehran, Iran) and the Ayatollah Khansari Hospital (Arak, Iran) were used to develop treatment plans using ۳DCRT, 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 ۶ 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. Results: The greatest PTV coverage was attained by VMAT, closely trailed by IMRT, both of which were considerably superior to ۳DCRT. Compared to ۳DCRT, 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. Conclusion and discussion: For the treatment of medulloblastoma, VMAT and IMRT are generally better than ۳DCRT because they offer better target coverage, conformance, and homogeneity. However, for many structures, IMRT showed unexpected superiority in OAR sparing.

کلیدواژه ها:

Radiotherapy ، ۳DCRT ، IMRT ، VMAT ، medulloblastoma ، dosimetry ، TCP ، NTCP ، secondary cancer risk