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

Abstract

Purpose This study aimed to identify the prognostic value of early metabolic response assessed using 18F-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.