A comprehensive dosimetric evaluation of using RapidArc volumetric-modulated arc therapy for the treatment of early-stage nasopharyngeal carcinoma.

The purpose of this study was to investigate the potential benefits of using triple-arc volumetric-intensity modulated arc radiotherapy (RapidArc (RA)) for the treatment of early-stage nasopharyngeal carcinoma (NPC). A comprehensive evaluation was performed including plan quality, integral doses, and peripheral doses. Twenty cases of stage I or II NPC were selected for this study. Nine-field sliding window IMRT, double-arc, and triple-arc RA treatment plans were compared with respect to target coverage, dose conformity, critical organ sparing, and integral doses. Measurement of peripheral doses was performed using thermoluminescent dosimeters in an anthropomorphic phantom. While similar conformity and target coverage were achieved by the three types of plans, triple-arc RA produced better sparing of parotid glands and spinal cord than double-arc RA or IMRT. Double-arc RA plans produced slightly inferior parotid sparing and dose homogeneity than the other two delivery methods. The monitor units (MU) required for triple-arc were about 50% less than those of IMRT plans, while there was no significant difference in the required MUs between triple-arc and double-arc RA plans. The peripheral dose in triple-arc RA was found to be 50% less compared to IMRT near abdominal and pelvic region. Triple-arc RA improves both the plan quality and treatment efficiency compared with IMRT for the treatment of early stage NPC. It has become the preferred choice of treatment delivery method for early stage NPC at our center.