Update: FDA approves new imaging drug for detecting spread of prostate cancer

Contents

STUDIES AT A GLANCE

This report is about:

FDA approval of a new type of PET scan to detect the spread of prostate cancer in men who are newly diagnosed with advanced disease and in those whose cancer has returned after treatment.

Why is this report important?

About seven percent of all prostate cancer are diagnosed at advanced stages (they have spread beyond the prostate). The FDA has granted approval to several imaging tests, including X-rays, magnetic resonance imaging (MRI) and computed tomography (CT scan), for detecting the spread of cancer and to help doctors determine the stage of the disease. However, all imaging techniques have limitations and can fail to detect small deposits of disease outside the prostate (metastasis). 

On December 1, 2020, the FDA approved a new imaging technique for detecting the spread of prostate cancer throughout the body. The technique uses a Gallium 68 PSMA-11 tracer which is detected by positron emission tomography (PET) scanning. The tracer is injected through a vein and moves throughout the body to attach to its target protein (e.g a protein found in cancer cells). PET scanners can then locate where the tracer has accumulated at high levels throughout the body, there by detecting any spread of caner.  PET scans can be used together with other imaging tests, such as CT (PET/CT) and MRI (PET/MRI).
 

Gallium 68 PMSA-11 tracer:

The recent FDA approval was based on two studies that looked at a new radioactive tracer called Gallium 68 PSMA-11 (Ga 68 PSMA-11). 

When injected in the body, Ga 68 PSMA-11 attaches to a protein called prostate-specific membrane antigen (PSMA). Although PSMA is found at low levels in normal prostate cells, it is found at high levels in prostate cancer cells. Over the past decade, more research has focused on radioactive tracers that bind to PMSA to locate spread of prostate cancer to other regions of the body. Accurately detecting cancer spread can help doctors stage prostate cancer and develop treatment plans.
 

Research Findings:

In the two multi-site studies that led to FDA approval, Ga 68 PSMA-11 was observed in two groups of men:

• men with newly diagnosed advanced prostate cancer  
• men whose cancer returned after treatment

Study #1

This first study included 325 men with newly diagnosed cancer who underwent imaging with Ga 68 PSMA-11 using PET/CT or PET/MRI scans.

All patients were considered at high-risk for advanced (metastatic) prostate cancer and were candidates for surgical removal of the prostate gland and nearby pelvic lymph nodes. Results showed that:

• among men who opted for surgical removal procedures, Ga 68 PSMA-11 was able to detect the spread of cancer to nearby pelvic lymph nodes. These results were confirmed by surgically removing the lymph nodes and then testing them for the presence of cancer cells.

Study #2

The second study included 635 men whose blood test suggested return of prostate cancer after treatment with radiation therapy or prostate removal.

All of these men underwent imaging with Ga 68 PSMA-11 using PET/CT or PET/MRI scans. Based on results of scans:

• Ga 68 PSMA-11 detected the spread of cancer to at least one body region outside the prostate gland in 74 percent of patients.
  • These regions included bone, pelvic lymph nodes and the soft tissue of the pelvis.
  • The spread of cancer detected by Ga 68 PSMA-11 was confirmed by additional tests, such as blood analysis, tissue sampling of affected organs and bone scan.
     

Side effects of Ga 68 PSMA-11

The most common side effects related to Ga 68 PSMA-11 tracer included:

• nausea
• diarrhea
• dizziness
   

Risks associated with Ga 68 PMSA-11

The FDA noted a possible risk for misdiagnosis of metastatic prostate cancer by Ga 68 PMSA-11. The tracer may bind to other types of cancer or certain nonmalignant regions, which may lead to errors.

In addition, because Ga 68 PSMA-11 is a radioactive agent, it contributes to a patient’s overall long-term radiation exposure, which could increase the risk for cancer. However, the risk of developing cancer due to the low radiation exposure by an imaging test is very unlikely, according to the American Cancer Society (“Understanding Radiation Risk from Imaging Tests”).
 

What does this mean for me?

If you are newly diagnosed with prostate cancer that your doctor suspects has spread to other organs or you have completed treatment and your doctor suspects your cancer has spread, you may want to talk to your doctor if Ga 68 PSMA-11 PET testing could benefit you.

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Posted 1/7/21