BERKELEY, CA (UroToday.com) - In clinical practice, positron emission tomography (PET) has traditionally been associated with the radiotracer analog of glucose 2-(18F) fluoro-2-desoxy-d-glucose (FDG), presenting a high sensitivity for the detection of the most prevalent malignant tumors with respect to staging, evaluation of response to treatment, and follow-up. On the other hand, other neoplasms such as carcinoma of the prostate, neuroendocrine tumors, and hepatocarcinomas, among others, do not generally demonstrate significant avidity for FDG.
Due to the diagnostic limitations of PET with FDG in the study of prostate cancer, new radiotracers such as 18F-fluoro-5 alpha-dehydrotestoterone, 11C-acetate, 11C-methionine, 11C-choline and 18F-fluorocholine (18F-FCH) have been developed. Among these, the choline analogs are the most frequently used.[1,2]
Choline is a small molecule which rapidly integrates into the cellular membrane as phosphatidylcholine on intravenous injection, becoming a metabolic marker of the membrane. Prostate cancer cells, even those of low- grade tumors, have increased choline-kinase activity and have affinity for choline.[3] However, this radiotracer is not useful in the differentiation between benign or malignant diseases of the prostate.[4]
Precise knowledge of the normal biodistribution of 18F-FCH is fundamental for correct interpretation of the study in patients with prostate cancer. In addition, it is important to know that some benign conditions, such as inflammatory lymph nodes, show a transitory increase in 18F-FCH with the “phenomenon of lymphatic lavage” reported in both inguinal and cervical lymph nodes, showing a reduction in uptake at 20 min. post-administration of the radiotracer.[4] Delayed or dynamic images may therefore be necessary to resolve the transitory increases in uptake in benign tissue.
Among the benign pathologies demonstrating uptake by 18F-FCH, osteoarthritis is of note in both advanced and early phases, especially in the presence of osteophytes. Moreover, increases in the uptake of 18F-FCH have been described in other benign processes in relation to lymphadenopathies, pulmonary nodules, pleuritis, thyroiditis, esophagitis, and otomastoiditis.[5]
In short, inflammatory phenomena are the most frequent causes of false positive results with 18F-FCH and may affect up to 15% of the patients. In a recent study, uptake of 18F-FCH was observed in systemic adenopathies in 5% of the patients with prostate cancer, defining these findings as not suspicious of malignancy.[5]
In our cases description, we reported other causes of pitfalls as osteogenic activity on a fracture callus, benign thyroid nodule, and infected sebaceous cyst.
Apart from unusual localizations of metastasis, the capacity of 18F-FCH should always be considered in the detection of inflammatory lesions in clinical practice. Thus, the integrated interpretation of PET findings within the clinical context of the patients is fundamental for correct elaboration of the diagnostic report.
Knowledge of the limitations induced by infectious/inflammatory or proliferative processes of benign origin in studies with 18F-FCH-PET allows false interpretations that reduce the specificity of this technique and are to be avoided.
References:
- Apolo AB, Pandit-Taskar N, Morris MJ. Novel tracers and their development for the imaging of metastatic prostate cancer. J Nucl Med. 2008;49:2031–41. 3.
- Krause BJ, Souvatzoglou M, Treiber U. Imaging of prostate cancer with PET/CT and radioactively labeled choline derivates. Urol Oncol. 2011, doi:10.1016/j.urolonc.2010.08.008 [Epub ahead of print].
- Nanni C, Fantini L, Nicolini S, Fanti S. Non-FDG PET. Clin Radiol.2010;65:536–48.
- Kwee SA, DeGrado TR, Talbot JN, Gutman F, Coel MN. Cancer imaging with fluorine-18-labeled choline derivatives. Semin Nucl Med. 2007;37:420–8.
- Schillaci O, Calabria F, Tavolozza M, Ciccio C, Carlani M, Caracciolo CR, et al.18F-choline PET/CT physiological distribution and pitfalls in image interpre- tation: experience in 80 patients with prostate cancer. Nucl Med Commun. 2010;31:39–45.
Written by:
A.M. García Vicente as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Servicio de Medicina Nuclear, Hospital General Universitario de Ciudad Real, Ciudad Real, España
Pitfalls with 18F-Choline PET/CT in patients with prostate cancer - Abstract
More Information about Beyond the Abstract