There has been a lot of hype and confusion about what is the best contrast for prostate cancer PET/CT scans. The two newest contrasts; (18)F-FACBC (anti1-amino-3-(18)F-fluorocyclobutane-1-carboxylic acid) and (11)C-choline both have their supporters and their detractors.

To try and evaluate the efficacy differences between these two contrasts in men who have suffered a bio-chemical recurrence after surgery researchers did a head to head evaluation of 100 consecutive men treated with surgery for prostate cancer and presenting with a rising PSA.

All of the men had (11)C-choline and (18)F-FACBC PET/CTs performed within 1 week and were off hormonal therapy at the time of the scans. The two contrasts 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 men the results were negative and in 25 men were positive with both the tracers, in eight men the results were positive with (18)F-FACBC but negative with (11)C-choline, and in five men the results were positive with (11)C-choline but negative with (18)F-FACBC.

Overall in 49 of the men the results were false-negative (FN), in two true-negative, in 24 true-positive (TP) and in none false-positive (FP) with both tracers.

The researchers perform many other statistical evaluations and concluded that (18)F-FACBC can be considered an alternative tracer that is superior to (11)C-choline in the setting of men with biochemical relapse after radical prostatectomy.

European Journal of NuclearMmedicine and Molecular Imaging. 2016 Mar 10 [Epub ahead of print]; Cristina Nanni, Lucia Zanoni, Cristian Pultrone, Riccardo Schiavina, Eugenio Brunocilla, Filippo Lodi, Claudio Malizia, Matteo Ferrari, Patrizio Rigatti, Cristina Fonti, Giuseppe Martorana, Stefano Fanti