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Researchers Identify Pitfall in PSMA PET Imaging Method

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Key Points

  • Some benign tissues also show increased PSMA expression and could potentially be confused with lymph node metastases, resulting in a possible misdiagnosis and unnecessary change in therapy regimen.
  • The study focused on PSMA-ligand uptake in cervical, coeliac and sacral ganglia. Researchers found that the uptake was above background levels in 401 patients (98.5% of participants).

Prostate-specific membrane antigen (PSMA) positron-emission tomography (PET) imaging has become a popular method for determining the stage of a patient’s prostate cancer. However, researchers have identified a pitfall in this imaging technique and are cautioning medical professionals to be aware of the potential for misdiagnosis when relying solely on PSMA PET. These findings were published by Rischpler et al in The Journal of Nuclear Medicine.

Potential for Misinterpretation With the Method

PSMA is a highly expressive enzyme in prostate cancer cells and metastases, which makes it a very useful target for imaging, allowing physicians to more easily diagnose the cancer and determine best treatments. However, past studies have noted that some benign tissues also show increased PSMA expression and could potentially be confused with lymph node metastases. These tissues include parts of the kidney, bowels, salivary glands, and ganglia along the sympathetic trunk. The result could be a misdiagnosis and unnecessary change in therapy regimen.

“It is important that nuclear medicine physicians be aware of this pitfall, as the interpretation of PSMA PET scans may have a substantial impact on therapy guidance,” said Christoph Rischpler, MD, of the Department of Nuclear Medicine at the Technical University of Munich.

The study focused on PSMA-ligand uptake in cervical, coeliac and sacral ganglia. The researchers analyzed 407 patients and compared the findings to adjacent lymph node metastases. They found that the uptake was above background levels in 401 patients—or 98.5% of participants.

Despite these findings, the researchers urge medical professionals not to completely abandon PSMA PET imaging. Instead, they suggest, nuclear medicine physicians should analyze PSMA-ligand uptake in conjunction with exact localization and configuration of the respective lesion to differentiate expressive ganglia from lymph node metastases and to avoid misinterpretation.

Dr. Rischpler stated, “We hope that an increased awareness among nuclear medicine physicians of this important pitfall helps to increase diagnostic accuracy and improve therapy guidance, preventing unnecessary procedures for [patients with prostate cancer].”

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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