Maxillary sinus inflammation assessment using FDG-PET/CT in head and neck cancer patients with photon, proton, and combined radiation therapy.

Background: Head and neck cancer (HNC) patients frequently develop post-radiation maxillary sinusitis. This study investigated how different radiation therapy (RT) modalities, photon, proton, and mixed photon/proton RT, affect maxillary sinus inflammation, using 2-[¹⁸F]-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT).

Methods: Seventy-seven HNC patients treated with RT (30 with photon, 20 with proton, and 27 with mixed photon/proton RT) underwent FDG-PET/CT imaging before and 3 months after treatment. Demographic information, tumor location, chemotherapy details, radiation dose (cGy), and post-radiation sinusitis ratings (scale 0-2) were collected. The mean standardized uptake value (SUVmean) of the maxillary sinus was measured by a radiologist with two years of experience using manually delineated regions of interest. Parametric paired t-tests were used to compare pre- and post-treatment SUVmeans for each RT modality. Pre-minus-post-treatment changes in SUVmean (ΔSUVmean) between RT modalities were compared using independent t-tests. Correlation between radiation dose and ΔSUVmean and correlation between ΔSUVmean and clinical sinusitis scores were assessed using Pearson correlation analysis.

Results: Photon RT was associated with a statistically significant increase in maxillary sinus SUVmean post-treatment (+14.32%, P = 0.0324), while proton RT and mixed photon/proton RT did not result in significant changes (-3.39%, P = 0.6549 and -5.33%, P = 0.4541, respectively). A significant difference was found between photon and mixed photon/proton RT (P = 0.0444), whereas the difference between photon and proton RT approached significance (P = 0.0790). Clinical inflammation ratings were highest for photon therapy (average 0.97), followed by mixed therapy (0.78), then proton therapy (0.65), though these differences were not statistically significant.

Conclusion: Our findings demonstrate that photon RT leads to significant increases in maxillary sinus SUVmean as measured by FDG-PET/CT, while proton and mixed photon/proton RT do not show statistically significant changes. These preliminary results suggest that proton-based radiation modalities may be associated with reduced maxillary sinus inflammatory activity compared to photon RT alone, though larger studies with longer follow-up are needed to establish clinical significance and patient outcomes.