The U.S. Food and Drug Administration ( FDA ) has approved Gallium 68 PSMA-11 ( Ga 68 PSMA-11 ), the first drug for positron emission tomography ( PET ) imaging of prostate-specific membrane antigen ( PSMA ) positive lesions in men with prostate cancer.
Ga 68 PSMA-11 is indicated for patients with suspected prostate cancer metastasis who are potentially curable by surgery or radiation therapy.
Ga 68 PSMA-11 is also indicated for patients with suspected prostate cancer recurrence based on elevated serum prostate-specific antigen ( PSA ) levels.
Ga 68 PSMA-11 is a radioactive diagnostic agent that is administered in the form of an intravenous injection.
Prostate cancer is the third most common form of cancer in the United States. It is estimated that there will be more than 190,000 new cases of prostate cancer and an estimated 33,000 deaths from this disease in 2020, according to the National Cancer Institute ( NCI ).
While computed tomography ( CT ) scans, magnetic resonance imaging ( MRI ) scans and bone scans are conventional methods commonly used to image patients with prostate cancer, these approaches are limited in detection of prostate cancer lesions.
F 18 Fluciclovine ( 18F-Fluciclovine ) and C 11 Choline ( 11C-Choline ) are two other PET drugs that are approved for prostate cancer imaging. However, they are only approved for use in patients with suspected cancer recurrence.
Once administered via injection, Ga 68 PSMA-11 binds to PSMA, which is an important pharmacologic target for prostate cancer imaging because prostate cancer cells usually contain elevated levels of the antigen.
As a radioactive drug that emits positrons, Ga 68 PSMA-11 can be imaged by PET to indicate the presence of PSMA-positive prostate cancer lesions in the tissues of the body.
The safety and efficacy of Ga 68 PSMA-11 were evaluated in two prospective clinical trials with a total of 960 men with prostate cancer who each received one injection of Ga 68 PSMA-11.
In the first trial, 325 patients with biopsy-proven prostate cancer underwent PET/CT or PET/MRI scans performed with Ga 68 PSMA-11.
These patients were candidates for surgical removal of the prostate gland and pelvic lymph nodes and were considered at higher risk for metastasis.
Among the patients who proceeded to surgery, those with positive readings in the pelvic lymph nodes on Ga 68 PSMA-11 PET had a clinically important rate of metastatic cancer confirmed by surgical pathology.
The availability of this information prior to treatment is expected to have important implications for patient care. For example, it may spare certain patients from undergoing unnecessary surgery.
The second trial enrolled 635 patients who had rising serum PSA levels after initial prostate surgery or radiotherapy, and thus had biochemical evidence of recurrent prostate cancer.
All of these patients received a single Ga 68 PSMA-11 PET/CT scan or PET/MR scan.
Based on the scans, 74% of these patients had at least one positive lesion detected by Ga 68 PSMA-11 PET in at least one body region ( bone, prostate bed, pelvic lymph node, or extra-pelvic soft tissue ).
In patients with positive Ga 68 PSMA-11 PET readings who had correlative tissue pathology from biopsies, results from baseline or follow-up imaging by conventional methods, and serial PSA levels available for comparison, local recurrence or metastasis of prostate cancer was confirmed in an estimated 91% of cases.
The second trial has demonstrated that Ga 68 PSMA-11 PET can detect sites of disease in patients with biochemical evidence of recurrent prostate cancer, thereby providing important information that may impact the approach to therapy.
No serious adverse reactions were attributed to Ga 68 PSMA-11. The most common adverse reactions to Ga 68 PSMA-11 were nausea, diarrhea and dizziness.
There is a risk for misdiagnosis because Ga 68 PSMA-11 binding may occur in other types of cancer as well as certain non-malignant processes which may lead to image interpretation errors.
There are radiation risks because Ga 68 PSMA-11 contributes to a patient’s overall long-term cumulative radiation exposure, which is associated with an increased risk for cancer. ( Xagena )
Source: FDA, 2020