Dosimetric study of Rapid Arc therapy during Craniospinal Irradiation in Adult patients

Context: Adult medulloblastomas are very rare and constitute only 1% of the central nervous system tumors in adults. CSI treatment is challenging in adults due to the long, irregular target volume, critical structures, and field matchings due to multiple fields. Aims: This retrospective dosimetric study of adult patients who underwent Craniospinal irradiation was done to get insight into the challenges in the treatment and advantages of using RapidArc technique. Materials and Methods: The computed dosimetric rapid arc planning data of 3 adult cases who underwent Craniospinal irradiation between November 2018 and June 2021 were studied. Results: In our study mean conformity index (range) was 0.95 (0.91–1) and Mean homogeneity index (range) was 0.11 (0.06–0.15). Mean dose to the lenses, lungs, heart, and kidneys was 6.4 Gy, 9.4 Gy, 5 Gy, and 7 Gy, respectively. Conclusions: Volumetric modulated arc therapy technique for Craniospinal irradiation gives conformal dose distribution within the target, better normal tissue sparing, and more homogeneous dose distribution in the field junctions without the need to move the junction.