[ 18 F] fluorodeoxyglucose PET/CT refines staging and treatment selection in high‐risk upper tract urothelial carcinoma

Objectives To evaluate the incremental clinical value of [ 18 F]fluorodeoxyglucose positron emission tomography/computed tomography ([ 18 F]FDG‐PET/CT) beyond contrast‐enhanced computed tomography (CECT) for primary staging of suspected high‐risk upper tract urothelial carcinoma (UTUC). Patients and Methods We conducted a consecutive paired‐imaging cohort study of patients with suspected high‐risk UTUC undergoing primary staging with both CECT and [ 18 F]FDG‐PET/CT at a tertiary cancer centre between 2013 and 2025. The primary outcome was clinically relevant stage migration, defined as a transition between non‐metastatic and metastatic disease, and its impact on multidisciplinary treatment recommendation. Secondary outcomes included diagnostic performance in cases with histopathological verification. Results Among 203 patients, [ 18 F]FDG‐PET/CT resulted in stage migration in 45 (22%), predominantly through upstaging (39 patients [19%]), comprising regional nodal upstaging in 19 patients (9.4%) and distant metastatic upstaging in 22 (11%), with both occurring in two patients. [ 18 F]FDG‐PET/CT led to treatment modification in 43 patients (21%). Stage migration was more frequent in the presence of CECT‐suspicious lymph nodes (odds ratio 3.4, 95% confidence interval 1.6–7.3). Among the 62 patients with histopathological verification, [ 18 F]FDG‐PET/CT demonstrated significantly higher sensitivity for nodal metastases than CECT (74% vs 33%) with similar specificity (89% vs 86%). Limitations include the retrospective single‐centre design and incomplete pathological confirmation, mostly due to neoadjuvant treatment and omission of surgery in metastatic disease. Conclusion [ 18 F]FDG‐PET/CT provides actionable staging information beyond CECT in high‐risk UTUC, leading to treatment modification in one in five patients and in half of those with CECT‐suspicious nodal disease. These findings support selective use of [ 18 F]FDG‐PET/CT in primary staging to refine treatment selection.