¹¹C-acetate PET/CT for evaluation of PSA relapse post radical prostatectomy

Objectives To evaluate the added value of ¹¹C-acetate PET/CT to ¹⁸F-FDG for the detection of prostate cancer (PCa) recurrence in patients with rising serum prostate specific antigen (PSA) level post radical prostatectomy.

Methods From July 2012 to June 2014, patients post radical prostatectomy with PSA relapse (defined as PSA>=0.2ng/mL) and referred for same-day ¹¹C-acetate & ¹⁸F-FDG PET/CT were consecutively recruited. Each PET/CT scan was reviewed by 2 nuclear medicine physicians in consensus for the evaluation of metastasis from PCa (pelvic or distant lymph node [LN], or distant organ metastasis). The level of confidence was scored for each scan in terms of tracer avidity (1=mild, 2=moderate, 3=markedly). The correlation between ¹¹C-acetate avidity and serum PSA level was analyzed.

Results 54 patients (age range:50~86y, mean=68.6±8.3y) with PSA relapse (range:0.3~26ng/mL, mean=4.3±6.7ng/mL) after radical prostatectomy were evaluated. ¹⁸F-FDG PET/CT detected metastatic recurrence in 25/54 (46.3%) patients: 8 in bone, 18 in LN and 1 in peritoneum. Combined ¹¹C-acetate & ¹⁸F-FDG PET/CT detected metastases in 37/54 (68.5%) patients, while 12/54 (22.2%) patients were by ¹¹C-acetate only: 5 bone and 9 LN metastases. The incremental diagnostic value of ¹¹C-acetate over ¹⁸F-FDG alone was significant (P<0.05). ¹¹C-acetate PET/CT also increased the level of confidence in 4/20 (20%) patients with tumors avid by both tracers. PSA level was significantly higher in ¹¹C-acetate-postive than negative patients (mean=5.9±8.2 vs 2.1±2.4ng/mL, P<0.05). The detection rate of ¹¹C-acetate PET/CT positively correlated with the relapsed PSA level (P<0.05): 38.5% (5/13), 53.3% (8/15), 62.5% (5/8), 71.4% (5/7) and 81.8% (9/11) for PSA<=1, >1~2, >2~3, >3~4 and >4ng/mL, respectively.

Conclusions ¹¹C-acetate PET/CT has an incremental value to ¹⁸F-FDG alone in enhancing the sensitivity and confidence for detection of PCa recurrence in patients with PSA relapse after radical prostatectomy. The chance for ¹¹C-acetate PET/CT to localize recurrent disease generally increases with higher PSA levels.