RT Journal Article SR Electronic T1 Effects of Proton, Photon, and Combined Radiotherapy on 18F-FDG Uptake in the Maxillary Sinus of Head and Neck Cancer Patients JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 3117 OP 3117 VO 63 IS supplement 2 A1 Min-Young Kim A1 Asad Siddiqi A1 William Raynor A1 Matthew Case A1 Yu-Cheng Chang A1 Thomas Werner A1 Mona-Elisabeth Revheim A1 Babak Saboury A1 Abass Alavi YR 2022 UL http://jnm.snmjournals.org/content/63/supplement_2/3117.abstract AB 3117 Introduction: Head and neck cancers (HNC) affect a variety of anatomic structures, including the oral cavity, oropharynx, nasopharynx, hypopharynx, larynx, salivary glands and sinuses. Along with surgical resection, HNC may be treated with radiation therapy (RT) as either definitive or adjuvant treatment. Radiation therapy for HNC often results in uncomfortable side effects for patients due to radiation induced inflammation to nearby normal tissue structures. The disease is often staged and surveilled using 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) This imaging modality may also be used to identify collateral damage from radiation therapy on neighboring tissues. This retrospective study aimed to investigate the use of FDG-PET/CT to evaluate radiation therapy-induced maxillary sinus inflammation in HNC patients.Methods: Sixty-four HNC patients were treated with photon, proton, or a combination of photon/proton radiotherapy (RT), along with chemotherapy. The patients underwent FDG-PET/CT imaging before RT and three months after treatment. OsiriX MD Software was used to assess the left and right maxillary sinuses for the mean standardized uptake value (SUVmean). Results: The maxillary sinuses of fifty-five HNC patients were evaluated. The SUVmean of the maxillary sinuses at three months post-treatment was significantly higher (1.32 post-RT vs. 1.14 pre-RT, p < 0.05) than pre-treatment for those exposed to photon-only RT. There were no significant differences before and after treatment for proton-only RT (1.30 post-RT vs. 1.13 pre-RT, p > 0.05) or combined proton and photon RT (1.11 post-RT vs. 1.18 pre-RT, p > 0.05). The summary of statistical data can be found in Table 1.Table 1. Maxillary sinus average mean standardized uptake values (Avg SUVmean in pre- and post-treatment scans of head-and-neck cancer patientsConclusions: A reproducible method to evaluate maxillary sinus inflammation in HNC patients following RT demonstrated that photon-only RT in HNC patients resulted in more collateral damage to the maxillary sinuses compared to proton-only RT or combined photon/proton RT. These results suggest that using proton RT in HNC cancer patients may limit clinically significant symptoms of sinusitis and improve the utility of follow-up surveillance imaging. Future prospective studies with increased sample size, evaluation of sinusitis symptoms following RT, and long-term follow-up evaluating the utility of FDG-PET/CT surveillance imaging in patients treated with proton vs photon RT are warranted.