The change of hypoxia and glucose metabolism before, during, and after IMRT for head and neck cancer

Objectives To investigate serial change of hypoxic state and glucose metabolism before, during, and after intensity modulated radiotherapy (IMRT) for head and neck cancer (HNC) using F-18 fluoromisonidazole positron emission tomography (FMISO-PET) and F-18 fluoro-deoxy-D-glucose PET (FDG-PET).

Methods This is a prospective study for both FMISO-PET and FDG-PET which were performed before IMRT, during IMRT (at 30Gy), and more than 1 month after completion of IMRT for patients with untreated HNC. Mean injection dose of FMISO was 11.2mCi, and FMISO-PET was scanned 4 hours after injection. Mean injection dose of FDG was 10.8mCi, and FDG-PET was scanned 1 hour after injection. PET images of primary lesion were semiquantitatively analyzed using SUVmax.

Results Six patients (male: 4, female: 2) have completed our protocol. Mean age was 55.3 years old. SUVmax of FMISO-PET decreased from 2.26 ± 0.69 before IMRT to 1.49 ± 0.22 during IMRT with no further decrease (1.49 ± 0.17) after IMRT. On the other hand, SUVmax of FDG-PET gradually reduced from 16.52 ± 6.44 before to 6.62 ± 3.21 during IMRT with further decrease (3.16 ± 1.24) after IMRT. Visual analysis showed that FMISO uptake was almost disappeared during IMRT. Although, FDG uptake reduced, it was not disappeared during IMRT.

Conclusions Both FMISO and FDG uptakes reduced during and after IMRT. But our preliminary results indicate that hypoxic condition seems to improve more rapidly than metabolic condition by IMRT. Further study is needed to see a long-term treatment effect after IMRT with these cases in relation to changes in FMISO and FDG uptake