Preliminary results of a prospective study of 18F-NAF PET/CT in prostate cancer.

103 Background: We performed a prospective study of 18F-NaF PET/CT bone scan (NaF) in the detection of bone metastases in men with prostate cancer. We previously reported that NaF identified more malignant lesions than Technetium-99m MDP bone scan (TcBS) (ASCO 2012 10589). This study evaluates the ability of NaF to detect bone metastasis in men with normal TcBS and also explores the change in NaF over 6 and 12 months compared to PSA changes. Methods: In a prospective 2-arm study, 60 men with prostate cancer (30 with and 30 without bone metastases by TcBS) were studied (ages 51-79). All had NaF and TcBS at baseline, followed by repeat NaF at 6 and 12 months. TcBS and NaF were reviewed by experienced nuclear medicine physicians. Abnormal foci of uptake on TcBS and NaF were classified as benign, malignant or indeterminate. Malignant uptake on NaF was confirmed by characteristic osteoblastic features on CT. Scan results were categorized as “positive” if any malignant lesion was present. In the 6 and 12 months follow up NaF, results were categorized as progression of disease (PD) = any new lesions or SUV increase > 30% in known lesions; stable disease (SD) = no new lesions or SUV changes < 30% in known lesions; and improvement of disease (ID) = resolution of known lesions or decrease SUV > 30% in known lesions. Results: 60 men have enrolled on study, 58 and 34 completed 6 and 12 month follow-up respectively. At baseline, 14 of 30 (47%) men with negative TcBS showed evidence of bone metastases in NaF (PSA mean 45); 7/14 had 2 baseline NaF and showed positive results in both, demonstrating reproducibility; 13/14 and 7/14 had follow up NaF at 6 and 12 months, respectively, all of which remained positive. In follow-up, 13/58 men at 6 months and 8/34 men at 12 months had PD from baseline on NaF, of whom 5/13 (38%) at 6 months and 5/8 (63%) at 12 months also had a PSA increase > 50%. All men who had PD on NaF at 6 months and had a follow-up scan at 12 months remained positive. 15 men at 6 months and 7 men at 12 months had ID on follow-up NaF, of which 11/15 (73%) and 6/7 (86%) had PSA decrease > 50% at 6 and 12 months, respectively. Conclusions: Early results of this ongoing NaF study are encouraging and suggest NaF identifies metastatic bone disease earlier than TcBS and correlates with changes in PSA. Clinical trial information: NCT01240551.