LAUSR

4544 Background: NaF+FDG PET imaging are used to assess soft tissue and bone metastases. The prognostic value of NaF+FDG PET in GU cancer pts was assessed as a secondary endpoint within a phase I trial of combination CaboNivoIpi. Methods: NaF+FDG PET scans were collected at baseline and cycle (C)3 day (D)1 for 50pts. Up to 50 lesions/patient were analyzed at baseline, up to 10 lesions/organ in case of extensive disease. Lesion number and whole-body metabolic tumor volume (wMTV) were recorded at baseline, C3D1 and percent change for FDG and NaF scans. Whole-body total lesion glycolysis (wTLG) and its percent change was obtained for FDG scans. Parameters were evaluated with respect to OS using Kaplan-Meier and log-rank, with quartiles, then refined to show strongest distinction, adjusting p-values to account for this exploration. Parameters with strongest OS association were also analyzed for associations with OS in urothelial carcinoma (UC) pts. Results: 50 pts, (UC (n = 20); others (renal cell, prostate, urachal/adenocarcinoma, germ cell, penile, bladder squamous cell (n = 2-7 each)). Median (m) overall survival (OS) was 23.9 months (mo) (95% CI: 13.7mo – NE) with 29.7mo m potential follow up and mOS of 24.7mo (95% CI: 13.7mo-NE) for UC. For FDG in all pts, wMTV: baseline ≤ vs > 51.6, mOS (NR vs 10mo, p = .0006), C3D1 ≤ vs > 85 mOS (25.9mo vs 5.1mo, p = .0001), percent change (0/increase vs decrease, mOS 14mo vs 25.9mo, p = .015); wTLG: baseline ≤ vs > 178, mOS (NR vs 11.5mo, p = .011), C3D1 ≤ vs > 300, mOS (25.9mo vs 8.3mo, p < .0001), percent change decrease vs increase, mOS (25.9mo vs 14.0mo, p = .016); and lesion number: baseline ≤ vs > 13, mOS (25.9mo vs 9.9mo, p = .0090), C3D1 ≤ vs > 13 mOS (25.9mo vs 9.9mo, p < .0001) significantly predicted OS. In UC pts, wMTV percent change (0/increase vs decrease, mOS 14mo vs. 25.9mo, p = .057), wTLG percent change decrease vs increase, mOS (NR vs 8.4mo, p = .0015), and lesion number C3D1 ≤ vs > 13 mOS (25.9mo vs 2.8mo, p = .022) significantly predicted OS. NaF parameters failed to do so. Conclusions: FDG wMTV and wTLG at baseline, C3D1, and percent change and lesion number at baseline and C3D1, predicted OS in GU cancer pts on CaboNivoIpi. Clinical trial information: NCT02496208.