ABSTRACT
PURPOSE: The aim of our study is to evaluate the prognostic impact of 18F-Choline (FCh) positron emission tomography (PET)/computed tomography (CT), CT alone and methylene diphophonate bone scan (MDP-BS) in prostate cancer (PCa) patients with biochemical relapse. METHODS: We retrospectively selected 58 patients who underwent, between June 2010 and February 2013, both FCh-PET/CT and MDP-BS within a maximum time interval of 5months. All patients had a biochemical PCa recurrence after radical prostatectomy and/or radiation therapy. Two independent observers reviewed FCh-PET/CT and MDP-BS images. The bone window of CT portion from FCh-PET/CT was separately assessed. Time to progression (TTP), skeletal event free survival (SES) and cancer specific survival (CSS) were defined as the length of time between imaging and progression of disease, skeletal related events and cancer specific mortality, respectively. A patient based and a K agreement analysis was used to compare the findings of all three imaging modalities. Kaplan-Meier and log-rank analysis were computed for survival assessment. A multivariate Cox regression analysis was used to identify the independent predictors for TTP. RESULTS: Bone metastases were detected in 22 (38%) patients at FCh-PET/CT, in 27 (47%) at MDP-BS and in 24 (41%) at CT. The agreement between FCh-PET/CT and MDP-BS, CT and MDP-BS, and FCh-PET/CT and CT were moderate/fair (respectively, k: 0.474, 0.267 and 0.424; all p<0.05). After 38months (IQR: 27-54months) of follow-up, 33 (57%) patients had a new recurrence of disease, 12 (21%) had skeletal related events and 19 (33%) died. Three subjects (5%) were lost during the observational period. At survival analyses, a worse TTP, SES and CSS were found in patients with a positive FCh-PET/CT at bone level than those with a negative scan (all p≤0.05). Conversely, any significant difference in TTP, SES and CSS was found for patients with both a positive MDP-BS and CT scan. At univariate analysis, a positive FCh-PET/CT at skeletal level was associated with all events (all p<0.05). However, only a positive FCh-PET/CT at any site was an independent prognostic variable of TTP (HR: 3.08; CI 95%: 1.85-9.05; p=0.04). CONCLUSIONS: PET/CT should be preferred to CT and BS in patients with prostate cancer with bone metastasis because it allows a better stratification of TTP, SES and CCS compared to CT and BS.