Clinical use of Dynamic 11C-Choline PET/CT in biochemical relapse of prostate cancer after radical treatment

1449 Objectives The real utility of Dynamic-11C-Choline-PET/CT (D-PET) in evaluation of local relapse and pelvic lymph-nodes has not been demonstrated yet. The aim of this retrospective study was to assess the use of D-PET in patients (pts) with rising PSA after prostatectomy candidates to RT. Methods 30 pts with rising PSA (range 0.94-6.5 ng/ml) after prostatectomy who underwent to RT on suspicious local or lymph-nodal disease revealed by 11C-Choline PET/CT, were identified retrospectively in our database. In addition to standard PET/CT acquisition (from vertex to mid-thigh), a post-injection D-PET study was performed focusing on the pelvis. Asymmetry and abnormal 11C-Choline uptake at prostate bed and/or lymph-nodes stations were used to define D-PET positivity. PSA levels and clinical outcome were available for all pts. Results D-PET showed tracer uptake on the prostate bed confirmed by standard PET/CT acquisition in 7/30 pts; 4/7 showed tracer uptake also on the pelvic lymph-nodes. All these 7/30 pts received RT at the site of suspicious local relapse and/or simultaneous integrated boost on the avid lymph-nodes following reduction of PSA (range 0-0.68ng/ml) and good control of disease (median PFS: 30,5 months). In 15/23 pts D-PET revealed 11C-Choline avid pelvic lymph-nodes that were treated by RT using PET/CT in the planning treatment obtaining sensible reduction of PSA levels and good clinical outcome. Only 4/15 pts had biochemical relapse after long time (PFS >24months). Mimicking a clinical scenario, D-PET was useful in the decision making to discriminate lymph-nodes uptake to urethral urine activity in 3/30 pts and to distinguish inflammatory lymph-nodes in 6/30 pts. These 9/30 pts did not received any local treatment showing no progression of disease during the follow-up. Conclusions 11C-Choline D-PET showed an optimal performance improving the evaluation of loco-regional relapse and could provide crucial information in guiding treatment of relapsing prostate cancer.