The potential benefit of swallowing sparing intensity modulated radiotherapy to reduce swallowing dysfunction: An in silico planning comparative study

Abstract

PurposeTo apply recently developed predictive models for swallowing dysfunction to compare the predicted probabilities of swallowing dysfunction for standard intensity modulated radiotherapy (ST-IMRT) and swallowing sparing IMRT (SW-IMRT). Materials and methodsThirty head and neck cancer patients who previously underwent radiotherapy for the bilateral neck were selected for this study. For each patient, ST-IMRT and SW-IMRT simultaneous integrated boost treatment plans were created. ST-IMRT treatment plan optimisation aimed at obtaining adequate target volume coverage and sparing of the parotid and submandibular glands as much as possible. Objectives for SW-IMRT were similar, with additional objectives to spare the organs at risk related to swallowing dysfunction (SWOARs). Dose-volume data with ST-IMRT and SW-IMRT and normal tissue complication probabilities for physician-rated and patient-rated swallowing dysfunction were calculated with recently developed predictive models. ResultsAll plans had adequate target volume coverage and dose to critical organs was within accepted limits. Sparing of parotid glands was similar for ST-IMRT and SW-IMRT. With SW-IMRT, the mean dose to the various SWOARs was reduced. Absolute dose values and dose reductions with SW-IMRT differed per patient and per SWOAR and depended on N stage and tumour location. The mean reduction in predicted physician-rated Radiation Therapy Oncology Group (RTOG) grade 2–4 swallowing dysfunction was 9% (range, 3–20%). Mean reductions of the probability of patient-rated moderate to severe complaints with regard to the swallowing of solid food, soft food, liquid food and choking when swallowing were 8%, 2%, 1% and 1%, respectively. ConclusionsNew predictive models for swallowing dysfunction were applied to show potential reductions in physician and patient-rated swallowing dysfunction with IMRT that was specifically optimised to spare SWOARs.