Dosimetric comparison of coplanar and non-coplanar volumetric-modulated arc therapy in head and neck cancer treated with radiotherapy

Abstract

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.

A Prospective Phase II Study of Automated Non-Coplanar VMAT for Recurrent Head and Neck Cancer: Initial Report of Feasibility, Safety, and Patient-Reported Outcomes

“…For higher dose (i.e., more proximal) structures such as the mandible and larynx, the average maximum dose differences were around 2 Gy, i.e., less than 50 cGy per fraction. This is consistent with the report by Gayen et al, who showed that the low dose spillage volume of V5Gy was marginally increased with non-coplanar VMAT, although V10Gy was reduced [40].…”

Evaluation of the correlation between dosimetric, geometric, and technical parameters of radiosurgery planning for multiple brain metastases

“…In Section 3.3, it was shown that there is a positive correlation between the target volumes and the number of noncoplanar arcs, corroborating this trend. Therefore, it should not be concluded that the V10Gy, V12Gy, and V14Gy would be larger when using noncoplanar arcs, because in our department, noncoplanar arcs are used when coplanar arcs do not achieve good results, as well as recent studies suggest that noncoplanar arcs can achieve better planning results 17‐21 …”

“…Therefore, it should not be concluded that the V10Gy, V12Gy, and V14Gy would be larger when using noncoplanar arcs, because in our department, noncoplanar arcs are used when coplanar arcs do not achieve good results, as well as recent studies suggest that noncoplanar arcs can achieve better planning results. 17 , 18 , 19 , 20 , 21 …”

Dosimetric Evaluation of Low-Dose Spillage Volumes for Head and Neck Cancer Using Intensity-Modulated Radiation Therapy and Volumetric Modulated Arc Therapy Treatment Techniques

“…The scatter contribution from the collimator and patient body along with softer energy spectrum outside the treatment field (compared with within the treatment field) plays a vital role in the irradiation dose to normal tissues outside the target volume [25,26]. Moreover, Fig.…”