Changes in acute response to radiation after implementation of new national guidelines for head and neck cancer

Purpose/Objective: New national guidelines (GL) for radiotherapy (RT) of head and neck cancer (HNC) were implemented at the beginning of 2013. One purpose of the new GL was to nationally standardise the expansion from GTV to high risk CTV (CTV1). This standardisation has resulted in change of volume of CTV1 for most institutions which previously used different margins. Change in CTV1 volume definition could influence the risk and time evolution of adverse effects e.g. mucositis. This study investigates change in acute response during RT in a centre where GTV to CTV1 margin was increased from 0 to 5mm. Materials and Methods: All patients (n=592) receiving curative RT for HNC from Jan 2011 to Sep 2014 were included, 292 patients treated according to the old GL and 300 according to the new GL. Tumour doses were 66-68 Gy in 33-34 fx with 5 or 6/10 fx/w. All were treated with IMRT except for simple glottic tumours. Acute skin and mucosal reactions were scored weekly during RT, and 2 and 8 weeks after (0 none, 1 erythema, 2 dry desquamation/patchy mucositis, 3 wet desquamation/confluent mucositis, 4 ulceration). Use of analgesics was recorded equivalently on a 5-point scale. Clinical endpoints were dichotomized, grade 0- 1 vs 2+ or 0-2 vs 3+. Potential change in actuarial cumulative incidence (One minus the Kaplan Meier estimator) of mucositis was tested using the log-rank test. To stratify for the potential effect between non-accelerated (5 fx/w) and accelerated (6/10 fx/w) treatments, a Cox regression analysis including the covariates: acceleration, old/new GL, and their interaction product was performed. Potential differences between patient demographics were tested using a chi-square test. Results: The new GL increased the risk of grade 2+ mucositis during RT (p = 0.02) as demonstrated by a ~20%-point increase at the end of RT for the non-accelerated group, but not in the accelerated group. In Cox regression, all covariates were significantly associated with grade 2+ and 3+ mucositis (acceleration, p