Reduction of the dose to the elective neck in head and neck squamous cell carcinoma,a randomized clinical trial using intensity modulated radiotherapy (IMRT). Dosimetrical analysis and effect on acute toxicity

Background and purpose

A randomized trial was initiated to investigate whether a reduction of the dose to the elective nodal sites and the swallowing apparatus delivered by IMRT would result in a reduction of acute and late side effects without compromising tumor control. The aim of this paper is to report on dosimetrical analysis and acute toxicity.

Materials & methods

Two-hundred patients were randomized. In the standard arm, elective nodal volumes (PTV_elect) were irradiated up to an equivalent dose of 50 Gy. In the experimental arm an equivalent dose of 40 Gy was prescribed to the PTV_elect. The dose to the swallowing apparatus was kept as low as possible without compromising therapeutic PTV (PTV_ther) coverage.

Results

No significant difference was seen between both arms concerning PTV_ther coverage. The median D₉₅ of the PTV_elect was significantly lower in the experimental arm (39.5 vs 49.8 Gy; p < 0.001). Concerning the organs at risk, the dose to swallowing structures and spinal cord was significantly reduced. There was no significant difference in acute toxicity. Three months after radiotherapy there was significantly less grade ?3 dysphagia in the experimental arm (2% vs 11%; p = 0.03). With a median follow-up of 6 months no significant differences were observed in locoregional control, disease free survival or overall survival.

Conclusions

Using IMRT we were able to significantly reduce the dose to the PTV_elect and several organs at risk without compromising PTV_ther coverage. This resulted in a significant reduction of severe dysphagia 3 months after radiotherapy. Further follow-up is necessary to investigate whether these observations translate into a benefit on late treatment related dysphagia without affecting treatment outcome.