Advanced Imaging Accelerates Metastatic Prostate Cancer Care

More than 250,000 Americans will be diagnosed with prostate cancer this year. While the percentage of localized disease is declining, the incidence of metastatic prostate cancer is on the rise. That disturbing trend makes the development of prostate specific membrane antigen (PSMA) PET imaging, an advanced diagnostic technique for identifying metastatic disease, both important and timely.

Named No. 2 on Cleveland Clinic’s list of top 10 medical innovations to watch in 2022, PSMA PET is already having a direct impact on patient care at Cleveland Clinic Florida since its introduction back in January of this year.

Tagging the PSMA protein

PSMA is a protein present at a low level in normal prostate tissue but occurs at much higher levels on the surface of prostate cancer cells. Tagging the PSMA protein with a radioactive tracer makes it is easily detectable on PET scans. “When combined with a CT scan or MRI, PSMA PET is substantially more likely to detect recurrent or metastatic prostate cancer than standard imaging techniques,” says Jacobo Kirsch, MD, Chair of the Cleveland Clinic Florida Imaging Institute.

The U.S. Food and Drug Administration has approved two radioactive imaging agents that bind to PSMA-positive lesions. The first is 68Ga-PSMA-11, approved in December 2020, followed by 18F-DCFPyL in May 2021. While studies show these radiotracers are comparable in their ability to detect prostate cancer cells, the PyL radiotracer is the only commercially available PSMA PET agent in South Florida.

Indications for PSMA PET

According to Dr. Kirsch, the addition of PSMA PET/CT to Cleveland Clinic Florida’s imaging arsenal has already identified a number of cases of metastatic prostate cancer that would have been missed by other radiotracers or imaging modalities alone. “Finding these metastases earlier, when they are much smaller, has a significant impact on treatment planning and hopefully will mean better outcomes for our patients,” he adds.

In one case, a 66-year-old patient more than six years out from a radical prostatectomy had a PSA of 0.236 ng/mL during routine follow up, which represents a minimally elevated level. After a CT scan found no evidence of metastatic disease, a subsequent PSMA PET/CT identified seven very small bone lesions within the spine, scapulae, and ribs.

This case demonstrates one of the two current indications for PSMA PET which are: 1) high-risk men who are candidates for initial definitive therapy, such as prostatectomy or radiation therapy; and 2) men treated for localized prostate cancer with suspected recurrence based on rising PSA levels.

“We know a detectable PSA following a prostatectomy is a red flag, as is a rising PSA after radiation therapy, and both would merit a PSMA PET,” Dr. Kirsch explains. “PSMA PET is also an important diagnostic tool for patients with castration-resistant prostate cancer.”

Outperforming conventional diagnostics

Most men in the United States diagnosed with high-risk, localized prostate cancer undergo a conventional CT scan and bone scan to determine if there is evidence of metastatic cancer. PSMA PET/CT was found to be 27% more accurate than this standard approach.

Initial studies also found that PSMA PET/CT outperformed fluciclovine-18F (Axumin ®) PET/CT, another diagnostic study used to identify metastatic tumors. It uses an amino acid-linked radioactive tracer, exploiting the ability of prostate cancer cells to absorb amino acids much more rapidly than normal cells.

“PSMA PET imaging is able to find smaller metastases than other imaging modalities while exposing patients to substantially lower radiation,” says Dr. Kirsch. “With our state-of-the art digital PET/CT at Cleveland Clinic Florida, we achieve a high degree of detectability and can characterize the smallest of lesions.”

Dr. Kirsch believes the PSMA PET/CT will soon become the new standard of care for detecting prostate cancer metastases and will open the door to new therapies. “Based on the most recent guidelines, recurrent or metastatic disease detected with PSMA PET imaging is a qualifying criteria for 177 Lu-PSMA radioligand therapy, a recently FDA approved treatment for metastatic castration-resistant prostate cancer,” he notes.

PSMA PET-CT imaging is offered at Cleveland Clinic Weston Hospital and will be available at Cleveland Clinic Martin Health and Cleveland Clinic Indian River Hospital’s Vero Radiology beginning in July. Contact Weston Hospital at 954.689.5110, Martin Health at 772.288.5817 or Vero Radiology at 772.562.0163 to schedule a patient appointment.