Early Metabolic Response Assessed Using (18)F-FDG-PET/CT for Image-Guided Intracavitary Brachytherapy Can Better Predict Treatment Outcomes in Patients with Cervical Cancer

PURPOSE: This study aimed to identify the prognostic value of early metabolic response assessed using (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) during radiation therapy (RT) for cervical cancer. MATERIALS AND METHODS: We identified 116 patients treated with definitive RT, including FDG-PET/CT–guided intracavitary brachytherapy, between 2009 and 2018. We calculated parameters including maximum (SUV(max)) and mean standardized uptake values (SUV(mean)), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for baseline FDG-PET/CT (PET(base)) and image-guided brachytherapy planning FDG-PET/CT (PET(IGBT)). Multivariable analyses of disease-free survival (DFS) and overall survival (OS) were performed. RESULTS: We observed a time-dependent decrease in PET parameters between PET(base) and PET(IGBT); ΔSUV(max), ΔSUV(mean), ΔMTV, and ΔTLG were 65%, 61%, 78%, and 93%, respectively. With a median follow-up of 59.5 months, the 5-year DFS and OS rates were 66% and 79%, respectively. Multivariable analysis demonstrated that ΔSUV(max) ≥ 50% was associated with favorable DFS (hazard ratio [HR], 2.56; 95% confidence interval [CI], 1.14 to 5.77) and OS (HR, 5.14; 95% CI, 1.55 to 17.01). Patients with ΔSUV(max) ≥ 50% (n=87) showed better DFS and OS than those with ΔSUV(max) < 50% (n=29) (DFS, 76% vs. 35%, p < 0.001; OS, 90% vs. 41%, p < 0.001, respectively). Adenocarcinoma was frequently observed in ΔSUV(max) < 50% compared to ΔSUV(max) ≥ 50% (27.6% vs. 10.3%, p=0.003). In addition, models incorporating metabolic parameters showed improved accuracy for predicting DFS (p=0.012) and OS (p=0.004) than models with clinicopathologic factors. CONCLUSION: Changes in metabolic parameters, especially those in SUV(max) by > 50%, can help improve survival outcome predictions for patients with cervical cancer treated with definitive RT.