The molecule is the first approved PET imaging agent that detects prostate cancer lesions by targeting the prostate-specific membrane antigen (PSMA) — a protein produced at high levels by prostate cancer cells.
It is approved for patients suspected of cancer recurrence, based on elevated blood levels of prostate-specific antigen (PSA), a prostate cancer biomarker. The agent also can be used for those with suspected prostate cancer metastasis — when the cancer spreads to distant regions in the body — who might be cured by surgery or radiation therapy.
Other PET agents have been approved for detecting recurrent prostate cancer, but none for men whose cancer is suspected of spreading.
“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,” Alex Gorovets, MD, acting deputy director of the office of specialty medicine in the FDA’s Center for Drug Evaluation and Research, said in a press release.
Ga 68 PSMA-11, developed by researchers at the University of California, Los Angeles and the University of California, San Francisco, is a radioactive agent meant to be given as an intravenous (into-the-bloodstream) injection prior to PET scanning.
Once inside the body, it binds and accumulates inside prostate cancer lesions containing the PSMA protein, allowing clinicians to visualize these lesions in PET scans.
The decision to approve Ga 68 PSMA-11 was based, according to the researchers, on the results from two clinical studies involving 960 men with prostate cancer suspected of either cancer recurrence or metastasis.
The first was a Phase 3 trial involving 635 patients suspected of prostate cancer recurrence based on elevated PSA levels after initial prostate cancer surgery or radiation therapy. In this trial, Ga 68 PSMA-11 detected recurrent prostate cancer in 74% of participants, according to the researchers, and these lesions were proven as prostate cancer via other methods in 91% of cases.
The second Phase 3 trial included 325 patients with a confirmed prostate cancer diagnosis — either newly diagnosed or a confirmed recurrence — who were candidates for surgery, but considered at high risk for metastasis.
Among those who had surgery, the men whose lymph nodes had signs of cancer on PET scans had a clinically important rate of metastatic cancer, which was confirmed by surgical pathology.
Having this information prior to treatment is expected to spare some patients from undergoing unnecessary surgery, the researchers said.
No serious adverse events, meaning undesirable side effects, occurred in either trial. The most common reactions included nausea, diarrhea, and dizziness.
The FDA noted that some risk for misdiagnosis exists, due to Ga 68 PSMA-11 binding to some other cancer types and to certain healthy tissues. There also is a degree of health risk from the compound’s radioactivity, which increases a patient’s long-term radiation exposure.
Yet, “Ga 68 PSMA-11 is an important tool that can aid health care providers in assessing prostate cancer,” Gorovets said.
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