Imaging agent identifies sites of PCa recurrence

October 4, 2018

Imaging with 18F fluciclovine PET/CT (Axumin) tomography identified sites of disease recurrence in a majority of prostate cancer patients with biochemical recurrence and led to changes in treatment course in 59% of men scanned.

Imaging with 18F-fluciclovine positron emission tomography/computed tomography identified sites of disease recurrence in a majority of prostate cancer patients with biochemical recurrence and led to changes in treatment course in 59% of men scanned, according to a recent study (J Urol Sept. 1, 2018 [epub ahead of print]).

Armed with information from 18F fluciclovine PET/CT (Axumin, Blue Earth Diagnostics), urologists and patients with suspected biochemical recurrence of prostate cancercould make more informed decisions about treatment. Researchers do not yet know if the information provided by the scan changes outcomes from treatment.

Also see: PCa care in elderly men costs Medicare $1.2 billion

“The dilemma with biochemical recurrence is that urologists, radiation therapists, and medical oncologists have to make an educated guess as to where the recurrence is. We would use things like the quickness with which the PSA recurred after therapy, or the PSA velocity, to infer whether that recurrence is somewhere locally, in the prostate or prostatic bed, or distantly, meaning metastatic to lymph nodes or the bone. The problem is that kind of guesswork was frequently inaccurate,” said Gerald L. Andriole, MD, of Washington University School of Medicine in St. Louis and lead author of the LOCATE trial, a prospective, multi-center, open-label study done at 15 U.S. sites.

“Now we have this imaging study that can show us where the site of recurrence is in most patients. And that can allow us to do smarter, more targeted therapies,” Dr. Andriole said.

Dr. Andriole and co-authors studied use of 18F fluciclovine, an FDA-approved molecular imaging agent for use in PET imaging in men with suspected prostate cancer recurrence, in 213 patients thought to have biochemical recurrence. They found 18F fluciclovine PET/CT was positive in 57% of patients, leading to often-major changes in treatment for more than half of the patients studied. Among the changes, three-quarters of the 60 patients who were going to have androgen deprivation therapy (ADT)changed post-scan to non-systemic salvage treatment.

Next:A promising advance

Having access to the imaging is a promising advance in metastasis-directed therapy, according to Dr. Andriole.

“Let’s say, in the case of a man who had a radical prostatectomy and several years later his PSA started to rise. He gets the scan and there’s an isolated lymph node somewhere in his body. If we direct therapy to that suspicious site, either by surgically removing it or by targeting radiation to it, in about a third of patients PSA will go to nearly undetectable. And PSA will go down in nearly every patient,” he said.

The scan appears to be more accurate than making educated guesses about prostate cancer recurrence, but it’s not perfect. In other studies where patients had 18F fluciclovinescans and histologic biopsies to confirm results, slightly more than 90% of the abnormal sites outside of the prostate were prostate cancer. About 70% of the sites within the prostate were found to be cancer, according to Dr. Andriole.

“The reason it may be a little lower in the prostate is not fully known, but it could be that the ability to target the specific abnormal site in the prostate is actually not as accurate as trying to target a site outside of the prostate,” he said.

Still, the implications of making more accurate treatment decisions for prostate cancer patients are huge, according to Dr. Andriole.

Read: Does early-life alcohol intake raise high-grade PCa risk?

“About 30% of patients who are treated for cure, whether by surgery or radiation therapy, are going to experience biochemical recurrence. There are close to 250,000 men diagnosed with prostate cancer each year and many of them are treated with curative intent or will be somewhere down the road,” he said.

There is research to suggest imaging can change patient outcomes. European researchers have found the use of PET scan using gallium with prostate-specific membrane antigen improved overall cause-specific survival for prostate cancer for patients who had metastasis-directed therapy versus patients who had standard of care therapy, according to Dr. Andriole. The European study is not definitive, but it’s reassuring, he said.

“It’s going to be important to do a trial of metastasis-directed therapy for patients whose recurrence is identified on these PET scans versus the standard of care approach,” he said.

Another next step is to look beyond PET scanning as a diagnostic application and study using PET scans to treat prostate cancer patients, he said.

“There is interesting early data suggesting that some PET scans can be used to treat patients who have prostate cancer,” he said. “That’s another tantalizingly interesting thing for urologists to keep an eye on down the road as our experience with these PET agents matures.”

 

The study was funded by Blue Earth Diagnostics. Dr. Andriole does research for the company but has no reported conflicts of interest.