Ed Weber, M.D., Editor
March – April, 2015

The new entry into whole-body PET/CT imaging for prostate cancer may be “coming soon (we hope) to a nuclear medicine department near you.” The name: anti-1-Amino-3-[18F]fluorocyclobutane-1-carboxylic acid — FACBC for short.

The FACBC scan offers two notable advantages as compared to the 11C-choline PET/CT:

  1. It is more sensitive, and therefore more accurate: sensitivity of 89%, specify of 69%, and an accuracy of 83% (Nanni et al., University of Bologna, Italy. Future Oncology. 2014).
  2. Secondly, and most importantly, the half-life for the tracer is 110 minutes ( compared to 17 minutes for the 11C-choline scan) and does not require an on-site cyclotron. It will be suitable for transport from the manufacturing site to the clinic. This feature will make this scan widely available.

The basic mechanism underlying imaging with this tracer is also different from the 11C scan, based on the incorporation of choline into the cell walls of proliferating tumors. The 18F-FACBC scan is dependent upon the cellular uptake of a radiolabled synthetic L-leucine analogue of the natural amino acid L-leucine required for protein metabolism. The uptake is “related to the functional activity of two different amino acid transporters, which appear to be upregulated in prostate cancer progression to metastatic disease” (Nanni, ibid).

Comparison of scans was reported by Nanni et al.,Clin Genitourin Cancer, Apr 2014, “18F-FACBC compared with 11C-choline PET/CT in patients with biochemical relapse after radical prostatectomy: a prospective study in 28 patients.

The mean PSA at relapse was 2.9 ng/mL ( range: 0.2-14.6). The detection rate of 11C scan was 17.8% compared to 35.7% for the FACBC study. All positive lesions detected in the 11C scan were imaged with FACBC, but “with the later radiotracer, 11 (61.1%) additional tumor were identified including 5 (17.8%) additional patients.

Appropriately, Nanni concluded “Further studies are required to assess the exact added value of this new tracer.

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