Explore and assess the utility of the routine 2-year post-treatment FDG PET/CT scan on head and neck squamous cell carcinoma patients

Background: Head and neck squamous cell carcinomas (HNSCCs) are common and highly aggressive malignancies with frequent recurrences following curative treatments. Currently, there is a trend of increasing disease prevalence, especially in the younger cohorts without history of smoking or excessive alcohol consumption. Therefore, optimizing secondary prevention may offer patients more treatment options and potentially prolong or improve quality of life (QOL). The current protocol for detecting recurrences varies between institutions, and generally consists of a 3- or 4-month post-treatment positron emission tomography (PET)/computed tomography (CT), with or without an additional 6- or 12-month post-treatment PET/CT. However, there is limited evidence regarding the effectiveness of long-term PET/CT surveillance. The objective of this study is to evaluate and assess the utility of a routine 2-year post-treatment fluorodeoxyglucose (FDG) PET/CT scan for asymptomatic HNSCC patients. Methods: Data of all asymptomatic HNSCC patients who underwent 2-year post-treatment PET/CT between 2010–2021 in a major tertiary head and neck cancer referral centre were retrospectively examined. Information regarding demographics, disease characteristics, and imaging outcomes was assessed. Results: A total of 154 asymptomatic HNSCC patients were identified, of which 6% (n=10) of patients had asymptomatic recurrences detected by 2-year PET/CT. These recurrences include six distant metastasis, three loco-regional recurrences, and one new primary cancer (esophageal carcinoma). Ninety-two patients who had negative 2-year PET/CT continued to be monitored for another three years, of which 4% (n=4) patients had recurrences. These recurrences include three loco-regional recurrences, and one malignancy of unknown origin, with a median diagnostic time of 45 months post-treatment. No significant relationship between demographics or disease characteristics and the recurrence rate was found. The diagnostic performances of the 2-year PET/CT were 100% in sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy [95% confidence interval (CI): 97.32–100%]. Conclusions: Routine surveillance for asymptomatic HNSCC patients using PET/CT at 2-year post-treatment can detect a substantial number of late recurrences, with excellent diagnostic accuracy. Based on this study, we recommend the continuation of routine surveillance using PET/CT at 2-year post-treatment for HNSCC patients.