About 12,000 people in the United States will be diagnosed with neuroendocrine tumors — sometimes called carcinoid tumors — each year. But what exactly are these tumors, where are they typically found and are they cancerous?
What are neuroendocrine tumors, and where are they usually found?
While the name “neuroendocrine” implies that these tumors involve both nerve cells and hormones, they are mainly thought to come from endocrine cells. The “neuro-” is more of a quirk of history.
Neuroendocrine tumors are cancers that can develop anywhere endocrine cells are present. Endocrine cells help regulate various body functions, such as growth, reproduction and metabolism. They are distributed throughout the body, but the most common places for tumors to develop from them are in the:
Are all neuroendocrine tumors cancerous?
The short answer is that neuroendocrine tumors are almost always cancerous. But each situation is unique, so it's impossible to capture the entire breadth of this disease in a simple yes or no answer.
Some neuroendocrine tumors are only classified as such because of how they appear under a microscope. But from a clinical standpoint, they almost never grow or spread, whether we do anything about them or not. Those cases only account for about 1% of all neuroendocrine tumors. But it’s important to mention them.
In some of the older systems for classifying neuroendocrine tumors, pathologists would describe them as either “benign” (non-cancerous) or “malignant” (cancerous), based on what the tumor cells looked like under a microscope. Unfortunately, those terms did not always accurately reflect whether the tumor would metastasize and behave aggressively or not, so they have been abandoned.
Today, almost all neuroendocrine tumors are considered malignant. There are just differences in how aggressive they are. Some spread easily. Others do not. But we consider all of them cancer.
What are the most common symptoms of neuroendocrine tumors?
Hormonal neuroendocrine symptoms include severe diarrhea, severe gastric ulcers, or uncontrolled blood sugar that responds poorly to treatment. The hormones produced can vary depending on the place in the body where the tumor originates.
Mechanical neuroendocrine symptoms relate to the function of one part of the body, such as a small bowel obstruction, or pain in a particular place. These symptoms occur because the tumor is physically pushing on another structure.
How are neuroendocrine tumors usually diagnosed?
Most patients fall into one of two groups.
Some seek help for symptoms, such as pain due to metastatic cancer. This most commonly occurs in the liver. So a patient will go to the doctor, thinking they have a gallbladder issue, and it turns out to be a neuroendocrine tumor in the liver. Other patients in this group will exhibit hormonal symptoms, which point doctors in the direction of a tumor as the source.
For others, the cancer is detected purely by chance. Maybe it was picked up during a colonoscopy, or during an X-ray or CT scan for a broken bone. These patients have no symptoms before their diagnosis.
Local treatments include surgery. Surgery is most useful when a tumor is just in one place or only one tumor (out of many) is causing a problem. But it may still be appropriate in certain other circumstances, even after a neuroendocrine tumor has spread. Our interventional radiologists have several technologies they can use to control individual tumors, too, particularly in the liver.
Systemic treatments are treatments we can give that target the cancer wherever it is in the body, even once it has spread. These include conventional chemotherapy, hormone therapy and targeted therapies.
The newest option is a type of systemic radiation called peptide receptor radionuclide therapy. Most neuroendocrine tumors have specific hormone receptors, so instead of giving patients the hormone therapy itself, we can use the hormone to drag the radiation to wherever the cancer is and bind to it, sparing most of the rest of the body from exposure.
This type of therapy was approved by the U.S. Food & Drug Administration in 2018. One study showed it reduced the rate at which neuroendocrine tumors progressed by 80%, so it’s a great option for some neuroendocrine patients.
It's important to note that there’s no “typical” treatment sequence for neuroendocrine tumors, though. There are hundreds of possibilities. And, each patient and care team will determine their specific treatment sequence based on their particular clinical situation as it evolves.
Can neuroendocrine tumors be cured?
Outcomes vary a lot when treating this disease. So, there’s no across-the-board answer.
But when we think about how a tumor is going to behave, we consider its:
When a tumor hasn’t spread yet, there’s a possibility of a cure, assuming it’s safe and appropriate to cut it out.
For some patients, though, surgery may carry more risks than the cancer itself. So, in those situations — especially if a tumor is not growing or spreading or causing troublesome symptoms — we may decide to just watch it carefully.
We can treat neuroendocrine tumors that have spread, but right now, we cannot cure metastatic neuroendocrine tumors.
Why are neuroendocrine tumors so challenging to treat?
Many patients with neuroendocrine tumors have hormonal symptoms that get progressively worse. So, they can experience symptoms for an average of five to seven years before finally receiving a neuroendocrine tumor diagnosis.
Because they have gone undiagnosed or misdiagnosed for so long, it can be very hard for some patients to rebuild a trusting relationship with their medical team. By the time they have an accurate diagnosis, they have often already moved from doctor to doctor seeking help, hearing over and over, “I don’t do this very often, so it’s not my strength,” or “What you have is rare and very weird.”
But whatever diagnosis you may have, it’s not rare or weird to us at MD Anderson. We care for hundreds of people with neuroendocrine tumors each year, so this will not be our first time treating them. And we are very happy to work together to find the best treatment plan for you.
Why should patients come to MD Anderson for neuroendocrine tumor treatment?
MD Anderson’s strength is two-fold.
First, we have specialists who care for patients with these tumors all day, every day. And we see plenty of rare and unusual cases even among neuroendocrine tumors. So our neuroendocrine tumor specialists have a lot of individual and collective experience deciding on which treatments to use and in what order.
Second is our clinical trial options. Most of the FDA-approved treatments for neuroendocrine tumors were tested at MD Anderson through clinical trials. We have been one of the largest contributors to their development, and we’ve played a substantial role in the studies of almost all of the drugs that have been approved in this field.
That means our patients had access to them long before most people in the general population. One example is everolimus, which James Yao, M.D., was studying as early as 2006 – six years before it was approved by the FDA.
We also played a leading role in establishing peptide receptor radionuclide therapy as a first-line option for patients with more aggressive neuroendocrine tumors through the NETTER-2 study. That means many of our patients contributed to that progress while also benefitting from the approach over the past 2 to 3 years.
Are there any clinical trials for patients with neuroendocrine tumors?
Yes. Many clinical trials are building on the success of peptide receptor radionuclide therapy right now. It’s not just one treatment; it’s more of an overarching concept of therapy.
The idea is that you use a particular protein on the front end to bind to cells and deliver a payload of radiation to your target at the back end. But you can change out the front or the back to get different combinations with different capabilities.
Lutathera, which uses Lutetium-177, is the only drug on the market that does this right now, but we have several clinical trials ongoing with it or other agents in the same family. One Phase III trial (NETTER-2) recently showed it could reduce the risk of disease progression by up to 72% when used as a front-line therapy for patients with more aggressive tumors. And we’re making progress toward having new agents deliver the radiation, such as actinium, another radioactive isotope.
Other clinical trials are building on targeted therapies and immunotherapy. Like many people, we are extremely interested in the promise of immunotherapy to one day help our patients live longer and better lives. The data we have right now suggests it’s not easy to use immunotherapy against neuroendocrine tumors, but we are looking at more combinations of agents and trying to figure out how to break the immune tolerance of these tumors.
Anything else you want newly diagnosed patients and their families to know about neuroendocrine tumors?
Where you go first for treatment matters. And the sequencing of that treatment matters. We believe that patients benefit most when they get the right treatment at the right time with doctors who specialize in treating these complex diseases.
We’re very proud that MD Anderson is one of the few places with such an experienced and dedicated team in this area.