Finding Smallest Traces of Recurrent Cancer. FDA Approves First PSMA-targeted PET Imaging Agent for Prostate Cancer

The U.S. Food and Drug Administration (FDA) has approved Gallium 68 PSMA-11 (Ga 68 PSMA-11) as a positron emission tomography or PET imaging agent for men with prostate cancer. 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.

The preceding appeared in the Dec. 7th online edition of Prostate Cancer News Today by Forest Ray.

FoundationOne Liquid CDx “Liquid Biopsy” Blood Test Gets Expanded FDA Approval

Roseate spoonbill in southwest Florida; photo by Shutterstock

If you are considering genetic testing to identify whether a potential therapy might be useful against your prostate cancer, this article may be helpful to you. This test can help identify genetic changes such as BRCA1, BRCA2 and ATM mutations in which case a corresponding targeted drug, such as olaparib (Lynparza), may be useful.

The Food and Drug Administration (FDA) has expanded the approved uses for a blood test, known as a liquid biopsy, that can help doctors pick the best treatments for some people with cancer. The test identifies cancer-related genetic changes in DNA from tumor cells that have been released into the blood.

The test, called FoundationOne Liquid CDx, was approved by FDA earlier this year to identify patients with lung and prostate cancer who can receive specific targeted drugs. When the test is used in this way, it’s known as a companion diagnostic.

Under the expanded approvals, announced by FDA in late October and early November, the use of the test as a companion diagnostic has been broadened to people with other cancers and other drugs not covered by the original approval. (See table.)

FoundationOne Liquid CDx and another cancer liquid biopsy test, Guardant360 CDx, were initially approved by FDA earlier in 2020. Both approvals covered use of the tests as companion diagnostics for several targeted therapies. The initial approvals also covered the use of the tests for general tumor profiling, meaning they can be used to identify a large number of specific cancer-related genetic changes, any of which may influence patients’ treatment choices or make them eligible to participate in certain clinical trials.

According to FDA, the expanded approval of FoundationOne Liquid CDx was based on analyses of the test’s use on blood samples from patients participating in clinical trials evaluating the targeted drugs.

In instances where the blood test does not identify the specific genetic change that means a patient can receive a corresponding targeted therapy, the agency advised that the patient’s tumor tissue should be analyzed “to determine if the specific mutations and alterations are present.”

Most of the above was published by the National Cancer Institute (NCI) Current Contents Blog on November 30th, 2020.