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18-04-2019 | Oncology | News | Article

68Ga-PSMA-11 PET shows ‘high accuracy’ for localizing recurrent prostate cancer

medwireNews: Positron emission tomography using 68gallium-labeled ligands of the prostate-specific membrane antigen (68Ga-PSMA-11 PET) is accurate, reproducible, and safe in localizing biochemically recurrent prostate cancer, according to the results of a prospective trial.

68Ga-PSMA-11 PET detected prostate cancer in 475 (75%) of 635 men aged a median of 65 years with a median prostate-specific antigen (PSA) level of 2.1 ng/ml, report Thomas Hope (University of California, San Francisco, USA) and co-researchers in JAMA Oncology.

Detection rates correlated significantly with prostate-specific antigen (PSA) levels, ranging from 38% among patients with a PSA below 0.5 ng/ml to 97% among those with a PSA of 5.0 ng/ml or above.

The test was highly accurate with 200 (92%) of 217 PET-positive patients and 229 (92%) of 249 PET-positive regions characterized as true positives on composite validation – comprising histopathologic analysis, PSA levels, and imaging data acquired during clinical routine – giving a positive predictive value (PPV) of 92%.

Similarly, 68Ga-PSMA-11 PET showed high accuracy on histopathologic validation, with a PPV of 84% on both a per-patient and per-region basis. Both results met the prespecified primary endpoint of a PPV of 70% or more.

PET false-positive results were reported in 17 patients, most commonly in the prostate or prostate bed, which the researchers suggest may be caused by urinary tracer excretion, inflammation, or post-therapeutic remodeling.

For each patient, images were interpreted by three independent and experienced readers who had received training ahead of the trial. Inter-reader agreement was “substantial” in all four regions measured, at 0.65 for the prostate bed, 0.73 for the pelvic nodes, 0.70 for extrapelvic soft tissues, and 0.78 for bone. These values, note the researchers, “were higher than those reported for the recently approved 18F-fluciclovine PET (0.36 to 0.57).”

There were no safety concerns with 68Ga-PSMA-11 PET. A total of 15 (2%) patients experienced grade 1 events following PET, and there were no adverse events higher than grade 1.

Until now, prospective data on the use of 68Ga-PSMA-11 PET have been lacking, despite it often being used on a compassionate basis and reported in a number of retrospective case series outside of the USA, say the study authors.

They conclude that their findings show that “68Ga-PSMA-11 PET provides early detection of metastases and contributes highly relevant information in a biochemical recurrence setting.”

By Catherine Booth

medwireNews is an independent medical news service provided by Springer Healthcare. © 2019 Springer Healthcare part of the Springer Nature group

JAMA Oncol 2019; doi:10.1001/jamaoncol.2019.0096

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