LETTER TO THE EDITOR Could choline PET play a role in malignancies other than prostate cancer? Cristina Nanni & Domenico Rubello & Stefano Fanti Received: 23 May 2007 / Accepted: 27 August 2007 / Published online: 26 September 2007 # Springer-Verlag 2007 Keywords Choline . PET . Prostate . Cancer Dear Sir, Prostate cancer is one of the most common cancer and is the second leading cause of death from malignancy among US men [1]. After observing that fluorine-18 fluorodeoxyglucose positron emission tomography ( 18 F-FDG-PET) is not sensitive enough in this field, in 1998, Hara et al. [2] introduced 11 C-choline PET for the evaluation of prostate cancer patients. The uptake mechanism of 11 C-choline by cancer cells is related to the increased proliferative activity, although it is not related to Ki67 [3]. In fact, Choline is one of the components of phosphatidylcholine, an essential element of phospholipids in the cell membrane, whose synthesis is up-regulated in cancer. 11 C-choline PET was proven to play a significant diagnostic role by several authors [4–6], in particular, for the detection of prostate cancer relapse sites. In fact, the uptake of 11 C-choline in prostate cancer cells is high, and the renal excretion is low, increasing the accuracy of the pelvis evaluation. In addition, the typical biodistribution of 11 C-choline (very high in the liver, pancreas, salivary glands, and kidneys but very low in the other organs) allows the evaluation of other anatomical sites beside the pelvis, in particular, the brain, the thorax, and the bones. So, many researchers tested it for the evaluation of 18 F-FDG-negative cancers or for the evaluation of physiologically increased 18 F-FDG-uptake areas. For example, as 18 F-FDG distributes to the brain, and the interpretation of the scan can be difficult in case of low grade brain malignancies, Ohtani et al. [7] tested 11 C- choline in 22 patients affected by different kinds of brain tumors (high grade and low grade) and benign diseases. The authors found that 11 C-choline PET has the potential to easily enable differentiation between low-grade and high- grade gliomas, but not to differentiate low-grade gliomas from non-neoplastic lesions, and that the combination of 11 C-choline PET and magnetic resonance (MR) imaging may provide an accurate means by which to identify high- grade gliomas. Fig. 1 shows a case of brain disease relapse depicted at 11 C-choline PET/CT in a patient previously treated for a glioblastoma. Another example is the evaluation of bladder cancer. Urothelial cancer, in fact, is known to be 18 F-FDG-negative in the majority of cases. Furthermore, the bladder is one of those sites in which unspecific presence of 18 F-FDG is found due to the renal excretion of the tracer. As choline is only excreted late by the kidneys, it may allow the evaluation of bladder cancer patients. Picchio et al. [8] analyzed 27 patients affected by urothelial bladder cancer. They found that their preliminary results suggest a possible role of 11 C-choline. In fact, 11 C-choline PET turned out to be comparable to computed tomography (CT) for detecting residual bladder cancer after TURB but appeared to be Eur J Nucl Med Mol Imaging (2008) 35:216–218 DOI 10.1007/s00259-007-0591-2 C. Nanni : S. Fanti Department of Nuclear Medicine, Policlinico S. Orsola Malpigli, Bologna University, Bologna, Italy D. Rubello (*) Nuclear Medicine Service, PET Unit, ‘S. Maria della Misericordia’ Hospital, Istituto Oncologico Veneto (IOV)-IRCCS, Viale Tre Martiri, 140, 45100 Rovigo, Italy e-mail: domenico.rubello@libero.it