The association of FDG PET/CT and NaF PET/CT with survival outcomes in patients (pts) with metastatic genitourinary malignancies (mGU) treated with cabozantinib + nivolumab +/- ipilimumab (CaboNivo +/- Ipi).

Abstract

452 Background: This study determined the association of functional imaging parameters obtained on FDG PET/CT and NaF PET/CT with OS for pts with mGU malignancies treated on a phase I study with CaboNivo +/- Ipi. Methods: Pts on this phase I study underwent sequential (1-hour apart) FDG PET/CT and NaF PET/CT imaging at baseline and at first-restaging (8 weeks follow up). Scan semi-quantitative parameters measures included: maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for FDG and MTV for NaF. Total lesion number was captured for all scans. The association of imaging parameters and survival was determined with Kaplan-Meier curves. Baseline values and percent change values were calculated. Results: 81 pts were included in the analysis. 67 (83%) were males; Median age was 63 (range 25-86); Histologically, 30 pts had urothelial carcinoma, 15 clear cell renal cell carcinoma, 9 germ cell tumors, 8 urachal/adenocarcinoma, 8 prostate cancer, 3 penile cancer, 3 squamous cell carcinoma, 3 renal medullary carcinoma, and 2 small cell (1 bladder, 1 prostate). All 81 had a baseline FDG PET scan, 78 pts received baseline NaF PET scans; 66 received both FDG PET and NaF PET baseline and follow up scans. 957 total lesions were detected on FDG PET across all histologies, 87 liver (9%), 252 lung (26%), 152 bone (16%), 411 lymph node (43%), and 55 other visceral metastases (6%). 414 total lesions were detected on NaF imaging. Low vs high baseline FDG MTV (31 vs 11 months, p = 0.0002), TLG (30 vs 11 months, p = 0.0004), Lesion number (49 vs 15 months, p = 0.0005), and SUVmax (25 vs 12 months, p = 0.025), FDG lesion number decrease or no change vs increase (24 vs 12 months, p = 0.0068), and low vs high baseline NaF MTV (26 vs 16 months, p = 0.007), and lesion number (26 vs 16 months, p = 0.007) showed the strongest associations with OS. A multivariable Cox analysis demonstrated that baseline FDG MTV (HR = 2.87, 95% CI 1.62-5.08, p = 0.0003) and FDG lesion number percent change (HR = 2.71, 95% CI 1.40-5.24, p = 0.0031) were jointly associated with OS. Conclusions: Baseline functional imaging parameters and percent change seen on follow imaging with FDG PET and NaF PET are prognostic in mGU pts treated with CaboNivo +/- ipi. Additional parameters and histologic subsets will be presented.