Abstract
1552
Objectives The restaging of patients with prostate cancer (PCa) and suspicious for bone metastasis is performed by several imaging modalities. However, until now, it is unclear which techniques can impact on overall survival (OS) and disease free survival (DFS). The aim of our study was to evaluate the prognostic impact of 18F-Choline (FCH) PET/CT, CT and bone scan (BS) in PCa patients with skeletal recurrences.
Methods From June 2010 to February 2013, we retrospectively selected 62 patients who underwent both FCH PET/CT and BS, within six months one from the other. All patients had a biochemical PCa recurrence after radical prostatectomy and/or radiation therapy. Two independent observers reviewed PET/CT and BS images for all sites of disease and particularly for bone involvement. The bone window of CT portion from PET/CT was separately assessed. OS was defined as the time from the radiological examinations to all-cause mortality. DFS was defined as the length of time between imaging and a new recurrence of disease. A patient based and a K agreement analysis were used to compare the findings of all three imaging modalities. Kaplan-Meier and log-rank analysis were computed for survival assessment. Univariate and multivariate Cox regression analysis were used to identify the independent prognostic variables for OS and DFS.
Results The median PSA values at the time of FCH PET/CT and BS were 3.5 ng/mL and 3.3 ng/mL, respectively (P>0.5). Bone metastases were detected in 25 (40%) patients at FCH PET/CT, in 30 (48%) at BS and in 27 (44%) at CT. The agreement between PET/CT and BS, CT and BS, and PET/CT and CT were fair (respectively, k: 0.513, 0.32 and 0.47; all p<0.05). After 36 months (IQR: 26-52 months) of follow-up, 36 (61%) patients had a new recurrence of disease and 20 (34%) died. Three subjects (5%) were lost during the observational period. A worse 60 month-DFS was found in patients with a positive PET/CT at bone level than those with a negative scan (41% vs. 16%; p= 0.011). Conversely, any significant difference in DFS was found for patients with a positive/negative BS and CT. At univariate analysis, a positive PET/CT at skeletal level and in other site were associated with a recurrence of disease and death (both p<0.05). However, only a positive PET/CT at all site was an independent prognostic variable of DFS (HR: 0.298; CI 95%: 0.105-0.846; p=0.023).
Conclusions From our study PET/CT should be preferred to CT and BS in the evaluation of bone metastatic prostate cancer. In this group of patients PET/CT allows a better stratification of OS and DFS compared to CT and BS. This has important implications in patients’ further treatments and in the management of patient’s quality of life. Additional studies are needed to compare 18F-Choline PET/CT with either MRI or new radioactive tracer.