On December 1, the U.S. Food and Drug Administration (FDA) approved gallium-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.
Gallium-68 PSMA-11 is indicated for patients with suspected prostate cancer metastasis whose disease is potentially curable with surgery or radiation therapy. The agent is also indicated for patients with suspected prostate cancer recurrence based on elevated serum prostate-specific antigen (PSA) levels. Gallium-68 PSMA-11 is a radioactive diagnostic agent that is administered in the form of an intravenous injection.
Gallium-68 PSMA-11 is an important tool that can aid health-care providers in assessing prostate cancer,” said Alex Gorovets, MD, Acting Deputy Director of the Office of Specialty Medicine in FDA’s Center for Drug Evaluation and Research. “With this first approval of a PSMA-targeted PET imaging drug for men with prostate cancer, providers now have a new imaging approach to detect whether or not the cancer has spread to other parts of the body.”
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. Fluciclovine and 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, gallium-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, gallium-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 gallium-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 the agent.
In the first trial, 325 patients with biopsy-proven prostate cancer underwent PET/CT or PET/MRI scans performed with gallium-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 gallium-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 gallium-68 PSMA-11 PET/CT scan or PET/MRI scan. Based on the scans, 74% of these patients had at least one positive lesion detected by gallium-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 gallium-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. Thus, the second trial demonstrated that gallium-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 gallium-68 PSMA-11. The most common adverse reactions to the agent were nausea, diarrhea, and dizziness. There is a risk for misdiagnosis because gallium-68 PSMA-11 binding may occur in other types of cancer, as well as certain nonmalignant processes, which may lead to image interpretation errors. There are radiation risks because gallium-68 PSMA-11 contributes to a patient’s overall long-term cumulative radiation exposure, which is associated with an increased risk for cancer.