Radiotherapy of Head and Neck Cancer Patients: Small Safety Margins with Daily Imaging or Larger Safety Margins? - Abstract
Objective: To evaluate differences of intensity-modulated radiotherapy (IMRT) with helical tomotherapy in head and neck cancer for two clinical scenarios: irradiation with a small safety margin (SM) and daily imaging, or irradiation with a larger safety margin in combination with less frequent imaging.
Materials and methods: Retrospective analysis of irradiation plannings of 10 head and neck patients with two different safety margins (3 mm (SPTV)/ 7mm (LPTV)) from CTV to PTV. Additionally for the SPTV daily imaging control was calculated. PTVs, conformity (CI) and homogeneity index (HI) and especially applied dose to organs at risk (OAR) were compared.
Results: As expected a difference was found regarding PTV volumes, while CI and HI showed no statistically significant differences. The exposure of the OARs external, parotids and mandible is up to 3.5 Gy lower for SPTV plans in combination with daily image control. Concerning the myelon, the difference is much smaller and shows slight advantages for the LPTV plans.
Conclusions: With SPTV including daily imaging and LPTV without imaging, comparable plans can be calculated in terms of HI and CI. With regard to OAR exposure, there are clear advantages for irradiation with small SM in combination with daily imaging