What are neuroendocrine tumors?
A neuroendocrine tumor (NET) occurs when cells of the body’s neuroendocrine system grow in an uncontrolled, abnormal manner. Neuroendocrine cells have traits similar to nerve cells and to the hormone-producing cells of the endocrine glands. Neuroendocrine cells are located in organs throughout the body and perform specific functions, such as regulating air and blood flow and controlling the speed at which food is moved through the gastrointestinal tract.
NETs are relatively rare and develop most commonly in the lungs, appendix, small intestine, rectum, and pancreas. Many NETs start in the digestive tract, as it has more neuroendocrine cells than any other part of the body. Some tumors grow slowly while others can be very aggressive and spread to other parts of the body (metastasize), most often to the liver or bone.
NETs may secrete higher-than-normal amounts of hormones, which can cause conditions including diabetes, flushing, and diarrhea. Because these symptoms resemble those of other diseases, such as irritable bowel syndrome (IBS) or Crohn’s disease, they are often misdiagnosed. Special blood tests can help accurately diagnose these tumors.
There are several types of NETs, including Gastro Intestinal (GI NETS), Pancreatic (PNETS), Lung NETS, medullary thyroid carcinomas (MTCs), pheochromocytomas, and neuroendocrine carcinomas of the skin (Merkel Cell Cancer). Treatment depends on the type of tumor and its location, whether it produces excess hormones, how aggressive it is, and whether it has spread. Advances in treatment have improved the length of survival for patients with NETs.
While relatively rare, NETs have the second largest prevalence of all GI cancers (colon is the largest), because many people continue to live with the disease. Over the last several decades the incidence (number of new diagnoses) has also been rising, which might be due to more awareness, improved diagnostic tools, or a change in definition.
PET/CT scans of 62 year-old woman with multiple hepatic secondary NET lesions (gastrinoma). At follow-up, patient showed partial response (PRRT plus somatostatin analogs).
What is molecular imaging?
Molecular imaging is a type of medical imaging that provides detailed pictures of what is happening inside the body at the molecular or cellular level. Where other diagnostic imaging procedures—such as x-rays, computed tomography (CT) and ultrasound— predominantly offer anatomical pictures, molecular imaging allows physicians to see how the body is functioning and to measure its chemical and biological processes.
Molecular imaging offers unique insights into the human body that enable physicians to personalize patient care. In terms of diagnosis, molecular imaging is able to:
As a tool for evaluating and managing the care of patients, molecular imaging studies help physicians:
Molecular imaging procedures are noninvasive, safe, and painless.
Physicians are using molecular imaging to:
Peptide receptor radionuclide therapy (PRRT) is a highly targeted and effective form of MRT with minimal side effects for treating NETs with an abundance (or overexpression) of somatostatin receptors. In PRRT, the patient receives an intravenous injection of a drug such as octreotide that is chemically bound to (or radiolabeled with) a radioactive material, mainly lutetium-177. Other radionuclides include yttrium-90, or indium-111. The radioactive octreotide attaches to somatostatin receptors on tumor cells, which are destroyed by the radiation.
What are the advantages of molecular imaging technologies for people with NET?
Is nuclear imaging (PET or SPECT) safe?
Many medical procedures have side effects and risks; the same is true of nuclear medicine diagnostic tests such as PET (Positron Emission Tomography) and SPECT (Single Photon Emission Computerized Tomography). Each procedure takes a certain amount of radiation to perform appropriately. Used in the right way for the right patient at the right time, nuclear medicine is very safe—the benefits of the procedure very far outweigh the potential risks.
Is PRRT safe?
All medical therapies involve risks and can have both short- and long-term side effects. Please discuss with your treating physician the safety profile of PRRT treatments compared to other options you may be considering.
Are molecular imaging technologies covered by insurance?
Check with your insurance company for specific information on your plan.
What is the future of molecular imaging and NETs?
A multicenter, randomized, phase III study (NETTER-1) comparing treatment with different versions of octreotide in patients with inoperable, progressive, somatostatin receptor-positive midgut carcinoid tumors was completed with positive results in 2015. As of this writing (August 2017), the Federal Drug Administration is considering an application for the approval of PRRT using Lu177 Dotatate. Imaging with Ga-68 DOTATATE was approved in the United States in June 2016 to assist in locating NETs for staging and restaging and managing the ongoing care of patients. Researchers are continuing to study how to improve molecular imaging and therapy for those living with NET.
The Society of Nuclear Medicine and Molecular Imaging (SNMMI) has updated patient presentations on our website at www.snmmi.org/NETVideos.
For a more detailed understanding of the incidence and prevalence of NETS, please refer to Dasari, Arvind, Chan Shen, Daniel Halperin, Bo Zhao, Shouhao Zhou, Ying Xu, Tina Shih, and James C. Yao. "Trends in the Incidence, Prevalence, and Survival Outcomes in Patients with Neuroendocrine Tumors in the United States." JAMA Oncology (2017).