PSMA-PET/CT for Prostate Cancer

Prostate cancer is the most frequently occurring male cancer in Belgium. Patients who have been treated for prostate cancer, i.e. by surgery and/or radiotherapy, in a substantial degree suffer from a tumor recurrence, often diagnosed by an increase in serum tumor marker PSA (prostate specific antigen) within the first few years. In these patients with evidence of a tumor recurrence after primary treatment, it is important to most exactly define the location(s) of tumor, to guide appropriate therapy by surgery, radiotherapy and/or hormonotherapy. In so-called oligo-metastatic disease targeted therapy may still be curative and prevent the disease from spreading to distant locations. Therefore it is of paramount importance to have an accurate tool of medical imaging to localize all possible locations to be treated.

With some patients, the PSA-value is so low, that conventional nuclear medicine bone scanning or radiological CT or MRI cannot determine where the metastases are. Therefore, [18F]-Choline PET-CT was introduced to improve diagnostic imaging performance. However, in 30 to 40 percent of patients choline-PET does not localize tumor either, especially in small tumors and/or very low PSA values.

The PSMA PET is already routinely used in many European centres, and has shown a superior accuracy in these patients as compared to conventional imaging techniques. This has been a very consistent finding in scientifically reported patient studies.

Most of these investigations have been performed with PSMA labeled with Gallium-68. The investigators in Ghent, as others, have labeled PSMA with Fluor-18. This tracer provides many advantages, including a higher production yield enabling more patients to be scanned. Also from a perspective of radioprotection and financial costs, Fluor-18 is a better choice. Moreover, several recent studies, comparing Fluor with Gallium modalities seem to suggest equivalent or better diagnostic results, possibly because of a lower aspecific background activity.