18F-FACBC (anti1-amino-3-18F-fluorocyclobutane-1-carboxylic acid) versus 11C-choline PET/CT in prostate cancer relapse: results of a prospective trial

Purpose To compare the accuracy of 18 F-FACBC and 11 C-choline PET/CT in patients radically treated for prostate cancer presenting with biochemical relapse. Methods This prospective study enrolled 100 consecutive patients radically treated for prostate cancer and presenting with rising PSA. Of these 100 patients, 89 were included in the analysis. All had biochemical relapse after radical prostatectomy (at least 3 months previously), had 11 C-choline and 18 F-FACBC PET/CT performed within 1 week and were off hormonal therapy at the time of the scans. The two tracers were compared directly in terms of overall positivity/negativity on both a per-patient basis and a per-site basis. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were calculated for both the tracers; follow-up at 1 year (including correlative imaging, PSA trend and pathology when available) was considered as the standard of reference. Results In 51 patients the results were negative and in 25 patients positive with both the tracers, in eight patients the results were positive with 18 F-FACBC but negative with 11 C-choline, and in five patients the results were positive with 11 C-choline but negative with 18 F-FACBC. Overall in 49 patients the results were false-negative (FN), in two true-negative, in 24 true-positive (TP) and in none false-positive (FP) with both tracers. In terms of discordances between the tracers: (1) in one patient, the result was FN with 11 C-choline but FP with 18 F-FACBC (lymph node), (2) in seven, FN with 11 C-choline but TP with 18 F-FACBC (lymph node in five, bone in one, local relapse in one), (3) in one, FP with 11 C-choline (lymph node) but TP with 18 F-FACBC (local relapse), (4) in two, FP with 11 C-choline (lymph nodes in one, local relapse in one) but FN with 18 F-FACBC, and (5) in three, TP with 11 C-choline (lymph nodes in two, bone in one) but FN with 18 F-FACBC. With 11 C-choline and 18 F-FACBC, sensitivities were 32 % and 37 %, specificities 40 % and 67 %, accuracies 32 % and 38 %, PPVs 90 % and 97 %, and NPVs 3 % and 4 %, respectively. Categorizing patients by PSA level (