Head and neck cancers form about 30% of the total malignancies registered in a year in India. More than 400,000 new cases are diagnosed per annum [1,2]. Radiotherapy plays a major role in the management of this diverse spectrum of malignancies in the definitive, adjuvant and palliative setting. The major proportion of patients in India present in the advanced stages of the disease which further cements the position of radiotherapy in the plan of management. In the radical scheme of treatment of head and cancers, Purpose: To evaluate the dosimetric variations in patients of head and neck cancer treated with definitive or adjuvant radiotherapy using optimized non-coplanar (ncVMAT) beams with coplanar (cVMAT) beams using volumetric arc therapy. Materials and Methods: Twenty-two patients of head and neck cancer that had received radiotherapy using VMAT in our department were retrospectively analyzed. Each of the patients was planned using coplanar and non-coplanar orientations using an optimized couch angle and fluences. We analyzed the Conformity Index (CI RTOG), Dose Homogeneity Index (DHI), Heterogeneity Index (HI RTOG), low dose volume, target and organs-at-risk coverage in both the plans without changing planning optimization parameters. Results: The prescription dose ranged from 60 Gy to 70 Gy. Using ncVMAT, CI RTOG , DHI and HI RTOG , and tumor coverage (ID 95%) had improved, low dose spillage volume in the body V 5Gy was increased and V 10Gy was reduced. Integral dose and intensity-modulated radiation therapy factor had increased in ncVMAT. In the case of non-coplanar beam arrangements, maximum dose (D max) of right and left humeral head were reduced significantly whereas apex of the right and left lung mean dose were increased. Conclusion: The use of ncVMAT produced better target coverage and sparing of the shoulder and soft tissue of the neck as well as the critical organ compared with the cVMAT in patients of head and neck malignancy.

Background: This study was conducted to assess the dosimetric impact of FFF beam plans on high-grade brain neoplasms using the VMAT technique when compared with FF beam plans. Material and Methods: Thirty patients with high-grade brain neoplasms, who had received radiotherapy using VMAT technique retrospectively were selected for this study. All the patients were planned for VMAT using 6MV_FF beam and the same plan was re-optimized using 6MV_FFF beam keeping the same dose constraint. Radiotherapy dose distribution on planning target volume (PTV) and organs at risk (OAR), target conformity index (CI), Homogeneity Index (HI), Low dose volume in the patient (V5, V10, V20, and V30), and Integral dose to the whole body in both plans were compared. Results: The PTV coverage and OAR’s showed no significant differences in dose distribution between the FFF and FF beam VMAT planning. There was a reduction of the average maximum dose in the right eye, left eye, right optic nerve, and left optic nerve using FFF beams. The reduction in average low dose volume was observed in V5, V10, V20, V30, and Mean Dose. Also, a significant reduction was observed in the integral dose to the whole body using the FFF beam. Conclusions: Using FFF beams with VMAT is doable for the treatment of high-grade brain neoplasms, and the delivery mode of the FFF beam in VMAT may yield similar results to FF beam which should be confirmed in a large scale prospective clinical trial.

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