Important Considerations When Diagnosing NETs



Andrew E. Hendifar, MD: Understanding the biology of neuroendocrine tumors is very important to understanding how to effectively treat our patients. The most important distinguishing feature is differentiation. You have well-differentiated tumors, and you have poorly differentiated tumors. The therapy, in general, for poorly differentiated is chemotherapy; for well-differentiated tumors, the cornerstone of therapy is somatostatin analog treatment.

The biology is also important to understand, as far as the site of location. Pancreatic tumors have certain distinct treatment algorithms compared with midgut tumors, hindgut tumors, and lung tumors. Although these tumors occur in many different parts of the body, some of the principles that cross tumor types include the importance of differentiation and the importance of somatostatin receptor expression based on somatostatin scintigraphy, like an Octreoscan or Gallium-68.

It’s very important to understand functionality of the tumors. Depending on whom you ask, it can mean any number of different things. The most important definition of a functional tumor is a tumor that produces a syndrome. Typically, it’s the carcinoid syndrome for midgut tumors. But it’s important to note that other tumors can have functional syndromes, including pancreatic tumors where you can have a glucagon-secreting tumor, an insulin, a proinsulin-secreting tumor, a VIP [vasoactive intestinal peptide] secreting tumor, or gastrin, or any number of other syndromes. These are all essentially important to diagnose in order to help manage therapy.

Another way of describing a tumor is based on whether or not it’s expressing the somatostatin receptor. Sometimes that can be considered as a functional tumor as well. That occurs when you check an Octreoscan, or a Gallium-68, or somatostatin receptor scintigraphy and you see that the tumor has an abundance of the somatostatin receptor type 2 [SSTR2]. That helps inform whether or not the patient would be a candidate for somatostatin analog therapy as well as peptide receptor radiotherapy.

A neuroendocrine tumor is a very heterogeneous disease. It can occur in any number of types of differentiation, grades, as well as sites. This makes it important to understand. Many times we can group the sites together, and there are some principles that overlap and can help inform these types of decisions. But actually, this information is very important. You have to understand the differentiation, you have to understand the grade, and you have to understand the site. Once you have those pieces of information, you can start to formulate a treatment plan for your patients.

Prognosis is also dependent on-site. For a particular patient, I’m not sure how useful it is as a prognostic because, of course, grade and differentiation might have more relevance than the actual site of disease. But for the physician to really put together an effective treatment plan, these are essential pieces of information.

Gastroenteropancreatic neuroendocrine tumors [GEP-NETs] can typically be divided into different groups or components. I would say that you have the hindgut, which includes the rectum and the colon. You have midgut tumors, which are your ileum and duodenal tumors. This is the most common site. You have pancreatic tumors. And oftentimes, gastric neuroendocrine tumors are also categorized as a GEP-NET. Gastric can be either type 1, type 2, or type 3. A type 1 gastric tumor occurs in the setting of atrophic gastritis. A type 2 gastric tumor is Zollinger—Ellison syndrome. It’s a gastrin-producing tumor of the pancreas. And finally, type 3 gastric neuroendocrine tumors are sporadic.

Transcript Edited for Clarity

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