Dose–volume analysis of locoregional recurrences in head and neck IMRT, as determined by deformable registration: A prospective multi-institutional trial

Abstract Background and purpose Although IMRT for head and neck cancer is widely accepted, the implications of sparing normal tissue immediately adjacent to target volumes are not well known. Materials and methods Between 2002 and 2007, 124 patients with head and neck cancer were treated with surgery and postoperative IMRT ( n  = 79) or definitive RT ( n  = 45). Locoregional recurrences were analyzed for location relative to target volumes, and dosimetry. Results With a median follow-up of 26.1 months, a total of 16 locoregional recurrences were observed. The five-year actuarial locoregional disease-free survival was 82% [95% CI, 72–90%]. Analysis of 18 distinct sites of locoregional failure revealed that five of these failures were within the high dose clinical target volume (CTV), nine failures were at the margin of the CTV, and four recurrences were outside the CTV. The mean dose delivered to these recurrent volumes was 63.1 Gy [range: 57–68 Gy], while the mean dose to the coolest 1 cc within each recurrence was 60.0 Gy [range: 51–67 Gy]. There were two periparotid recurrences observed. Conclusions We observed excellent locoregional control rates overall. The majority of recurrences occur within high dose regions of the neck and not near the spared parotid glands.