3728 - Prognostic Value of a Partial Metabolic Response on Post-Treatment PET/CT in Locally Advanced Cervical Cancer
Presenter(s)
P. K. Hinman1, R. Jin2, B. Wankhar3, E. Janowski4, and K. Romano5; 1University of Virginia, School of Medicine, Charlottesville, VA, 2University of Virginia, Department of Public Health Sciences, Division of Biostatistics, Charlottesville, VA, 3University of Virginia, Department of Radiology and Medical Imaging, Charlottesville, VA, 4Department of Radiation Oncology, University of Virginia, Charlottesville, VA, 5University of Virginia, Department of Radiation Oncology, Charlottesville, VA
Purpose/Objective(s): Treatment response assessed by FDG PET/CT is an established prognostic factor in locally advanced cervical cancer (LACC). While a complete metabolic response (CR) is associated with favorable outcomes and progressive disease (PD) with poor outcomes, a partial metabolic response (PR) has intermediate outcomes and lacks PET/CT parameters for further risk stratification. This study aimed to identify quantitative PET/CT thresholds that predict clinical outcomes in LACC patients with a PR.
Materials/Methods: This retrospective review included LACC patients treated from 2007 to 2025 with definitive chemoradiation (CRT) and brachytherapy. All patients had pre- and post-treatment PET/CTs. Patient, treatment, and imaging characteristics were collected. Patients were stratified into three response groups based on the post-treatment PET/CT: CR (no residual abnormal FDG uptake), PR (residual FDG avidity at any original site), or PD (new FDG avid sites). Percent reduction in SUVmax (?SUVmax) was calculated as the relative decrease from the pre-treatment to the post-treatment value. Kaplan-Meier (KM) survival analysis was performed to evaluate 5-year overall survival (OS) and 5-year disease-free survival (DFS), and were compared using the log-rank test. A 5-year cumulative incidence analysis was conducted to present local (LF), regional (RF), and distant failure (DM), and comparisons were made using Gray’s test.
Results: 211 patients met inclusion criteria. The median age was 48.6 years (range, 19.4-86.5), most had FIGO stage III disease (58 stage I, 64 stage II, 77 stage III, 12 stage IV), with squamous cell carcinoma histology predominating (78.7%). Post-treatment PET/CT demonstrated a CR in 37.0% (n=78), PR in 43.6% (n=92), and PD in 19.4% (n=41). On KM analysis, OS and DFS differed across metabolic response groups (both p<0.0001), with the best outcomes in CR, intermediate in PR, and the poorest in PD. Within the PR subgroup, a lower ?SUVmax was associated with worse DFS (=66.0%, p=0.0075) and OS (<55.5%, p=0.033). Likewise, post-treatment SUVmax >6.0 was associated with worse OS and DFS (both p<0.0001). Using endpoint-specific post-treatment SUVmax cutoffs, the cumulative incidence of LF (75% vs 11%, p<0.001), RF (44% vs 12%, p=0.01), and DM (44% vs 10%, p=0.007) was higher among patients with elevated post-treatment SUVmax. On multivariable analysis, SUVmax >6.0 was independently associated with decreased DFS in the PR subgroup (HR 14.8, 95% CI 6.09-35.96; p<0.001).
Conclusion: In this single-institution experience of LACC, we identified ?SUVmax and post-treatment SUVmax thresholds that significantly predict survival and treatment failure in patients with a PR on post-treatment PET/CT. These findings highlight the potential of quantitative PET/CT parameters to improve post-treatment risk stratification and guide surveillance strategies in LACC.