11C-acetate PET/CT imaging of prostate cancer: Detection of recurrent disease in patients with PSA relapse following radical prostatectomy.

Abstract

e15080 Background: Patients with rising PSA after definitive local therapy of prostate carcinoma (PC) often present a diagnostic dilemma. A local recurrence or metastatic lymphnode lesions would be amenable to additional local therapy, whereas distant metastases usually require androgen deprivation. In this prospective study the effectiveness of 11C-acetate PET (AC-PET) matched with corresponding CT scans in pats. with PSA relapse following radical prostatectomy (RP) was evaluated. Methods: 45 pats. with histologically confirmed PC were enrolled in this study because of rising PSA following RP (n = 39) or radiotherapy (RTx) (n=6). Whole-body PET images were obtained after iv - administration of 1,000 MBq of 11C-acetate, CT from the neck to the pelvic floor was performed additionally. An image overlay of corresponding CT and PET scans was done using a specific image software (developed in Max Planck Institute, Cologne, Germany). Results: Out of 45 pats. n=17 were AC-PET pos. PSA in 8 of this subset was between 0.9 and 1.45 ng/mL, in 7 pats. between 2.7 and 7.3 ng/mL, and 2 pats. had a PSA of 19.2 and 23.1 ng/mL, respectively. Analysing the AC-PET pos. patients, in 6/17 AC-PET demonstrated lymphnode metastases, in 3/6 metastatic lesions were histopathologically confirmed, in the remaining 3 unspecific inflammatory tissue alterations were identified. In 4 pats. with corresponding AC-PET and CT scans RTx of proven lymphnode metastases was performed followed by decreasing PSA . After diagnostic work-up with PET and CT, 7/17 pats. were treated with hormone manipulation (6/7) or chemotherapy (1/7), in this AC-PET pos. subgroup CT had revealed tumour lesions in only 3 of them. Combining the pats. having undergone surgery and RTx (n=10) there were 7/10 true pos. in terms of AC-PET. In 5 / 10 PSA was < 2.0 ng/mL, in the remaining 5 PSA distribution was from 5.4 to 23.1 ng/mL. PPV (AC-PET pos): 0.824. Updated results will be presented. Conclusions: Although AC-PET seems to be a promising tool in the detection of recurrent PC even with PSA <2 ng/mL, false pos. pats. with a different metabolism marked by 11C-acetate decrease the specifity of the approach. Thus there is still more specific tracer requirement. No significant financial relationships to disclose.