Prostate cancer is the most common type of cancer in male subjects and it is the second most common cause of death, following cancer, in developed countries.
Radical prostatectomy and radiotherapy is the first-line treatment for prostate cancer that is confined to the prostate gland. Selection of treatment is based on the extent the tumor spread.
Cross-sectional imaging studies, such as computed tomography (CT) and Magnetic Resonance Imaging (MRI), and functional imaging studies, such as F-18 FDG PET, F18 Choline PET and Ga-68 PSMA, contribute to ability of visualizing metastatic foci.
Elevated PSA in patients, who have undergone surgery, is referred as “biochemical recurrence” that is witnessed in approximately 15-40% of patients. Guidelines issued by European Association of Urology defines biochemical recurrence as PSA reading = 0.2 ng/ml in postoperative period and >2 ng/ml after radiotherapy.
Existence of metastasis after recurrence is the principal factor that determines the selection of treatment. If there is no metastasis and salvage therapies are available, systemic treatment is given.
PSMA is a surface antigen that is found in 95% of prostate cancer cells. Risk of metastasis or recurrence increases in aggressive tumors.
Studies conducted on radionuclide-labeled peptides (PMSA), also known as Ga-68, show that this method is more accurate for visualizing recurrences and metastases of prostate cancer in comparison with other imaging methods.
The higher PSA level, the higher the positivity rate of the test. For example, positivity rate of the test is 47.1% and 96.8% for PSA level below 0.2 ng/ml and above 2 ng/ml, respectively.
Ga-68 PSMA PET/CT enables selection of patients who are eligible for radionuclide therapy (theranostics), such as Lu-177 (Lutetium 177).
Patients with tumor that show uptake Ga-68 PSMA and can be visualized on PET/CT scan are eligible for Lu-177. The smart molecule of PSMA binds to Lu-177 rather than Ga-68 and it is intravenously injected. Lu-177 uptake is absorbed by tumor cells that are ablated with Beta rays emitted.