Purpose: To investigate the feasibility of fluorine-18-labeled fluoromisonidazole positron emission tomography/computed tomography ((18)F-FMISO PET/CT)-guided intensity-modulated radiotherapy (IMRT) in dose escalation to attack the hypoxic volume of a tumor mass without increasing the normal tissue dose in head and neck cancer patients.
Materials and methods: Eight consecutive head and neck cancer patients underwent (18)F-FMISO PET/CT simulation. Hypoxic tumor volume (HTV) was defined using a tumor-to-cerebellum ratio (T/C) of 1.3 as the threshold for (18)F-FMISO PET/CT. Dose-escalation plans for treating HTVs using (18)F-FMISO PET/CT-guided IMRT were performed for these patients. The standard plan was 72Gy to the gross tumor volume (GTV) administered as 30 daily fractions of 2.4Gy. In biologically optimized IMRT plans, the daily dose to the HTV ranged from 2.6 to 3.6Gy. Dose-volume histograms (DVHs) were generated as part of each plan, and the results of planning were analyzed.
Results: Dose-escalation IMRT plans, delivering 30 daily doses of 2.6Gy (total of 78Gy) to the HTVs without increases in normal tissue doses, were feasible for six patients. Further acceptable dose escalation on HTV depended primarily on the primary tumor site and the extent of disease.
Conclusions: It was possible to dose escalate the HTV radiation to 78Gy in six of eight head and neck cancer patients using (18)F-FMISO PET/CT-guided IMRT.
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