Abstract
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Objectives Preliminarily investigate whole-body quantification of metabolically-active tumor volume (MATV) and total lesion activity (TLA) (product of lesion mean standardized uptake value and MATV) on 18F-fluorocholine (FC) PET/CT as prognostic markers in metastatic castrate-resistant prostate cancer (CRPC).
Methods Whole body FC PET/CT was performed in 20 patients with CRPC defined by rising prostate specific antigen (PSA) levels despite total androgen blockade. PET volumetric regions of interest were defined with activity-based thresholds to measure tumor MATV and TLA. Estimates of whole-body tumor burden based on net MATV and net TLA were analyzed in association with serum PSA level and overall survival (OS).
Results Metastases were evident on all 20 scans. Mean net MATV was 255 ± 100 cc and mean net TLA was 1166 ± 461 g. PSA level at the time of PET was significantly correlated with net MATV and net TLA (Spearman rho 0.53 (p=0.016) and 0.54 (p=0.014), respectively). Thirteen patients survived over a follow-up period of 19 months median duration (range 11 to 31 months). On Kaplan-Meier analyses, decreased OS was significantly associated with net MATV > 255 cc (estimated mean survival time 10.3 months versus 13.2 months for MATV <= 255 cc, p = 0.007) and net TLA > 1166 g (estimated mean survival time 10.9 months versus 13.2 months for TLA <= 1166 g, p = 0.001). Net MATV and net TLA, but not PSA level, PSA doubling time, or subsequent treatment type, were also significant predictors of mortality in univariate and age-adjusted hazard regression models.
Conclusions Higher tumor burden quantified by MATV and TLA on whole-body FC PET/CT was associated with increased mortality in this study of patients with metastatic CRPC. These results support further investigation of the potential prognostic value of FC PET/CT in a broader series of patients, including those receiving chemotherapy and other more recent treatments for advanced prostate cancer.
Research Support This study was supported by NIH/NCI grant R21CA139687-02.