SU-E-T-694: Significant Skin Dose Differences Between IMRT and VMAT and Between Boost and Integrated Treatment Regimens for Treating Head and Neck and Other Cancer Site Patients

Purpose: The purpose of this study is to evaluate 1) dose to skin between VMAT and IMRT treatment techniques for targets in the head and neck, pelvis, and brain; 2) to determine if the treatment dose and fractionation regimen impacts the skin dose between traditional sequential boost and integrated boost regimens for head and neck patients.Methods and Materials: A total of 19 patients and 48 plans were evaluated. Eclipse (v11) treatment planning system was used to plan nine head and neck patients, five Prostate patients and five Brain patients with VMAT and static field IMRT. The mean skin dose and the maximum dose to a contiguous 2 cm^3 volume for head and neck plans and brain plans and a contiguous 5 cm^3 volume for pelvis plans, was compared for each treatment technique. Three of nine head and neck patients utilized an integrated boost regimen. One integrated boost plan was re-planned with IMRT and VMAT using a traditional boost regimen. Results: For targets located in the head and neck VMAT reduced the mean dose and contiguous hot spot most noticeably in the shoulder region, by 5.6% and 5.4% respectively. When using an integrated boost regimen the contiguous hot spot skin dose in the shoulder was larger on average than a traditional boost pattern by 26.5% and the mean skin dose was larger by 1.7%. VMAT techniques largely decrease the contiguous hot spot in skin in the pelvis by an average of 36% compared with IMRT. Conclusions: For the same target coverage, VMAT can reduce the skin dose in all regions of the body, but more noticeably in pelvis and the shoulders in head and neck patients. In head and neck patients using integrated boost regimens lead to higher shoulder skin doses compared to traditional boost regimens.