PET Scan Based on Lizard Saliva Reliably Detects Benign Tumors in Pancreas

By MedImaging International staff writers
Posted on 22 Oct 2024

Image: PET/CT scans of a patient with suspected insulinoma and a cross-sectional view of the torso (Photo courtesy of J. Nucl. Med.; doi.org/10.2967/jnumed.124.268158)

The pancreas contains cells known as beta cells that produce insulin. Insulin is a hormone that assists the body in absorbing sugar from the bloodstream and storing it in areas such as muscle cells, helping to regulate blood sugar levels. In rare instances, the beta cells can malfunction, leading to the formation of a benign tumor called an insulinoma. Although this tumor almost never spreads, it can still cause issues due to the excessive production of insulin, resulting in low blood sugar levels. Various imaging techniques such as CT, MRI, and PET scans are available, but they frequently fail to detect these insulinomas, despite the symptoms caused by low blood sugar. Surgical removal of the tumor alleviates the problem, but identifying its location beforehand is crucial. Blood tests cannot confirm the tumor's presence or pinpoint its location. Now, a new PET scan has shown promise in reliably detecting benign tumors in the pancreas.

This innovative scan, known as the Exendin-PET scan, was developed by researchers at Radboud University Medical Center (Nijmegen, Netherlands) and enables the precise localization of insulinomas. The scan is based on a substance derived from the saliva of the Gila monster, a lizard native to the deserts of the United States. The researchers knew that this substance binds specifically to a molecule found on these tumors, known as the GLP1 receptor. However, since the original substance from saliva was not very stable in the human body, they created a more chemically stable variant called Exendin. The team then attached a radioactive substance to Exendin, allowing it to be visualized during a PET scan. This mildly radioactive version of Exendin appears to effectively detect insulinomas.

The researchers had previously published findings from a study involving children, where the insulinoma was congenital. In their latest research, published in the Journal of Nuclear Medicine, they reported results from a study involving adults, where the insulinoma developed over time. The study included 69 adult patients suspected of having insulinomas. The Exendin-PET scan successfully detected tumors in 95% of the patients, compared to 65% with the current PET scan. While the existing PET scan typically detects the tumor when combined with CT and MRI, in 13% of cases, the insulinoma was visible only on the new scan. The next step is to implement the Exendin-PET scan in clinics as the standard diagnostic tool for individuals suspected of having an insulinoma. Researchers will evaluate how this scan enhances patients' quality of life and the potential cost savings if other imaging techniques, such as CT and MRI, are no longer necessary.

“We believe the new scan can replace all other scans,” said Marti Boss, first author of the study. “All the insulinomas we found with the new scan were removed, and all those patients were completely cured after surgery, even though some had been sick for decades.”