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

To compare the accuracy of ¹⁸F-FACBC and ¹¹C-choline PET/CT in patients radically treated for prostate cancer presenting with biochemical relapse.

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 ¹¹C-choline and ¹⁸F-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.

In 51 patients the results were negative and in 25 patients positive with both the tracers, in eight patients the results were positive with ¹⁸F-FACBC but negative with ¹¹C-choline, and in five patients the results were positive with ¹¹C-choline but negative with ¹⁸F-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 ¹¹C-choline but FP with ¹⁸F-FACBC (lymph node), (2) in seven, FN with ¹¹C-choline but TP with ¹⁸F-FACBC (lymph node in five, bone in one, local relapse in one), (3) in one, FP with ¹¹C-choline (lymph node) but TP with ¹⁸F-FACBC (local relapse), (4) in two, FP with ¹¹C-choline (lymph nodes in one, local relapse in one) but FN with ¹⁸F-FACBC, and (5) in three, TP with ¹¹C-choline (lymph nodes in two, bone in one) but FN with ¹⁸F-FACBC. With ¹¹C-choline and ¹⁸F-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 (<1 ng/ml 28 patients, 1 – <2 ng/ml 28 patients, 2 – <3 ng/ml 11 patients, ≥3 ng/ml 22 patients), the number (percent) of patients with TP findings were generally higher with ¹⁸F-FACBC than with ¹¹C-choline: six patients (21 %) and four patients (14 %), eight patients (29 %) and eight patients (29 %), five patients (45 %) and four patients (36 %), and 13 patients (59 %) and 11 patients (50 %), respectively.

¹⁸F-FACBC can be considered an alternative tracer superior to ¹¹C-choline in the setting of patients with biochemical relapse after radical prostatectomy.