Trial Information

Recent publications have suggested the use of 11C-acetate as another PET tracer for tumor
imaging. The accumulation of 11C-acetate in tumor cells is related to the highly active
lipid metabolism in the cell membrane associated with tumor growth. 11C-acetate is channeled
into the tricarboxylic acid cycle via acetyl coenzyme A and then incorporated via
phosphatidylcholine into the cell membrane's phopholipids. Possible biochemical paths of
acetate incorporation or accumulation include (a) entering the Krebs cycle from acetyl
coenzyme A (acetyl CoA) or as an intermediate metabolite, (b) esterification to form acetyl
CoA as a major precursor in ß-oxidation for fatty acid synthesis, (c) combining with glycine
in heme synthesis, and (d) through citrate for cholesterol synthesis. Of all of these
possible metabolic pathways, participation in free fatty acid (lipid) synthesis is believed
to be the dominant method of incorporation in tumors.

The clinical data on the role of 11C-acetate PET in human tumors is being accumulated. Most
clinical studies have investigated the role of 11C-acetate PET in detection of prostate
cancer. 11C-acetate PET was found valuable in the detection of recurrent prostate cancer,
both in the prostate bed, lymph nodes and distant metastases. The main advantage of
11C-acetate is that it does not show physiological accumulation in the urinary bladder as is
the case with 18F -FDG and therefore may be appropriate for the detection of active pelvic
disease.

Comparing the uptake of 18F-FDG and of 11C-acetate in patients with lung carcinoma, the
latter was found superior in the identification of a bronchiolo-alveolar carcinoma which
often show no intense FDG uptake.

In the case of hepatic masses, well-differentiated HCC tumors were detect by 11C-acetate
while poorly differentiated types were detected by 18F-FDG.

These data suggest that 11C-acetate PET may be valuable in the detection of
well-differentiation slow growing tumors and may have a complementary role to the routinely
used 18F-FDG.