PET-based imaging improves metastases detection in biochemically recurrent prostate cancer - Journal of Clinical Pathways

By Marilynn Larkin

NEW YORK (Reuters Health) - Gallium-68 prostate-specific membrane antigen positron emission tomography (Ga-68 PSMA PET) accurately detects metastases in biochemically recurrent prostate cancer, particularly at low prostate-specific antigen (PSA) levels, researchers say.

"Historically, conventional imaging modalities have included computerized tomography and whole body radionucleotide bone scans," Dr. Marlon Perera of the University of Melbourne in Victoria, Australia told Reuters Health by email. "While cost-effective and readily available, these conventional imaging modalities are fraught with limited accuracy."

"Ga-68 PSMA PET is a novel imaging technique," he said. "PSMA is a transmembrane ligand that is expressed on prostatic cells. Excitingly, the expression of PSMA increases with increasing cellular dysplasia (i.e., more malignant). Accordingly, this represents an ideal target for imaging in prostate cancer."

In a 2016 paper in European Urology, Perera's team reported a meta-analysis of 18 studies involving 1,306 patients that showed "significantly superior accuracy, sensitivity and specificity" for Ga-68 PSMA PET compared with conventional imaging (http://bit.ly/2YyIqH1).

For the current study, the researchers expanded the meta-analysis, including 37 articles involving 4,790 patients.

As reported online February 14, also in European Urology, in men with biochemical recurrence, positive Ga-68-PSMA PET scans increased with higher pre-PET PSA levels.

Specifically, for PSA categories 0-0.19, 0.2-0.49, 0.5-0.99, 1-1.99, and 2 ng/ml or greater, the percentages of positive scans were 33%, 45%, 59%, 75%, and 95%, respectively.

No significant differences in Ga-68 PSMA PET positivity and Gleason score were noted. Patients with a Gleason sum of 7 or less had positivity of 72% compared with 80% in patients with a Gleason sum of 8 or more.

"In the biochemical recurrence setting, local recurrence was identified in 22% post prostatectomy and 52% post radiotherapy," Dr. Perera noted. "Radiotherapy cohorts also had higher rates of positivity in extrapelvic lymphadenopathy and bone metastases."

"A further novel finding of our meta-analysis identified interesting patterns of disease based on Ga-68 PSMA PET," he said. "In the primary setting, Ga-68 PSMA PET identified intraprostatic (local) prostate cancer in 90%."

He acknowledged that the study did not take potential selection bias into account.

Dr. Ash Tewari, Chair of urology at the Icahn School of Medicine at Mount Sinai in New York City, said Ga-68 PSMA PET "is still not FDA approved in the United States, but many of us have access to it because of research collaboration, research activity."

"But in Europe, it is available very easily and I have sent many patients to European institutions that have the largest experience in doing PSMA scans," he told Reuters Health by phone.

"The bottom line is that above a certain PSA level, a gallium PSMA scan is of use because it tells us exactly where the recurrence is happening," he said. "It has a reasonable sensitivity and accuracy and I don't think there is any other test available right now which does as well as this."

"Also, this meta-analysis is very clear in stating that it is not being recommended, at least based on this data, to for pretreatment staging," he added. "It has not yet been proven for that."

SOURCE: http://bit.ly/2THuTJo and http://bit.ly/2TF9EYS

Eur Urol 2019.

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