Role of 18F-FDG PET/CT in the assessment of therapy response and clinical outcome in metastatic renal cell carcinoma treated with tyrosine kinase inhibitors or immunotherapy

This study aimed to determine the role and prognostic significance of 18F-FDG PET/CT on treatment response and survival outcomes in metastatic renal cell carcinoma patients treated with immunotherapy or tyrosine kinase inhibitors (TKIs). Forty patients scheduled for a standard treatment protocol with TKIs (n = 17; group-1) or PD-1 inhibitors (nivolumab, n = 23; group-2) were evaluated by 18F-FDG PET/CT. Peak standardized uptake value corrected for lean body mass (SULpeak) and maximum standardized uptake value (SUVmax) were calculated, and their relationship to treatment response was evaluated. Complete response (CR) in three patients, partial response (PR) in two patients and stable disease (SD) in eight patients were observed in group-1, and the results were as follows for group-2: PR in seven and SD in five patients. At a mean of 17.5-month observation period (range, 7-47), 35.2% of patients progressed, and 23.5% achieved a CR, and no recurrence was observed on PET/CT scans during follow-up. Among all patients enrolled in the study, the 5-year OS in patients with progressive disease (PD) was significantly shorter than patients with clinical benefit (CB = CR and PR and SD) (P = 0.016). Significant differences in both ΔSULpeak and ΔSUVmax were found between PD versus CB (P = 0.001 and P < 0.001, respectively). 18F-FDG-PET/CT can accurately assess therapy response and predict patient outcome in metastatic RCC. 18F-FDG PET/CT may facilitate patient management by evaluating the biological and immunological responses to treatment in patients treated with TKIs or ICIs.