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.

Objective: 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).

Patients And Methods: 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.

Results: 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).

Conclusion: 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.