Research led by the Radboudumc has developed a PET scan that detects benign tumors (insulinomas) in the pancreas with high reliability. With current scans, these insulinomas often cannot be found, even though they cause symptoms due to low blood sugar levels. These types of tumors almost never spread, but they can cause problems. Too high a production of insulin results in too little sugar in the blood.
Once the tumor is found, surgery is possible. Inside the pancreas are cells that make insulin, called beta cells. Insulin is a hormone that causes the body to remove sugar from the blood and store it in muscle cells, for example. Thus, insulin regulates blood sugar levels in the body. In rare cases, the beta cells derail and a benign tumor, an insulinoma, develops.
Diagnosis and research
“Often it takes a long time for people to get a diagnosis. We can do blood tests, but they cannot confirm whether the cause is a tumor and where it is located. And beyond that, there are several scans available: CT, MRI and PET. But the insulinoma does not always show up well on those,” explains Marti Boss, first author of the publication.
Removing the tumor with surgery solves the problems, but that requires knowing where the tumor is. Martin Gotthardt, Professor of Nuclear Medicine at the Radboudumc explains that in the past, surgeons used to cut slices off the pancreas if they encountered the tumor. That sometimes meant the pancreas was virtually gone. Living without a pancreas is possible but it leads to severe diabetes. You then must watch your blood sugar levels all the time. Therefore, better scans of the pancreas are highly desirable.
New scan
Gotthardt and his team developed an entirely new scan, the so-called Exendin-PET scan, which allows them to accurately locate insulinomas. Previously, they published the results of a study in children in whom the insulinoma is congenital. Now they show the findings of a study in adults, in which the insulinoma developed slowly.
The study involved 69 adult patients with suspected insulinoma. Using the Exendin-PET scan, the researchers found the tumors in 95% of the patients, compared with 65% using the current PET scan. When combined with CT and MRI, the current PET scan usually still found the tumor, but in 13% of cases the insulinoma was only visible on the new scan.
Lizard
The new scan is based on a substance in the saliva of the gila monster, a type of lizard that lives in desert areas in the United States. Gotthardt says it was already known that this substance can bind specifically to a molecule on these tumors, the GLP1 receptor. Because the substance from saliva in the human body turned out not to be so stable, they therefore created a more chemically stable variant called. Exendin. To this, a radioactive substance is coupled so that it is visible on a PET scan. OP that way, Exendin brings insulinomas into proper focus.
Standard procedure
The next step is to bring the Exendin PET scan into the clinic as the standard scan for people with suspected insulinoma. To do this, the researchers will analyze how the scan improves patients' quality of life and how much money can be saved if other scans such as CT and MRI are no longer needed. In addition, in a new research project (LightCure), Gotthardt's team is investigating the possibilities of using Exendin to treat insulinomas.
Researchers at LUMC recently succeeded in using new, advanced techniques to penetrate deeper into tumors than ever before. This allows them to map the metabolism of individual cells in tumor tissue. The researchers can see which cells are in the tumor and how they behave. This science can contribute to the development of new therapies against cancer. In the study published in the scientific journal Nature Methods, the researchers describe how the combination of the two techniques give a better idea of the so-called tumor environment.
