Clinical management of tumour volume changes in VMAT head & neck radiation treatment

Abstract

The impact of changing anatomy due to tumour shrinkage was assessed for a VMAT head & neck plan optimized according to our centre's planning protocol. A custom-built wax phantom accommodating ion chamber, MOSFET, EBT3 film and Fricke-xylenol orange-gelatin (FXG) gel dosimeters and a variable size bolus 'tumour' was used in the investigation. Results indicate that the practice of initiating a patient re-scan and verification plan is appropriate when a change in external body contour greater than 1 cm compared to the original anatomy is observed.