About 12,000 people 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.
Basically, 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 lungs, small intestines and pancreas.
Are all neuroendocrine tumors cancerous?
The short answer is yes.
In some of the older systems for classifying neuroendocrine tumors, pathologists would describe them as either “benign” (non-cancerous) or “malignant” (cancerous), based on the appearance of the tumor cells under a microscope. Unfortunately, those terms did not always accurately reflect whether the tumor would metastasize and behave aggressively or not.
Now, all neuroendocrine tumors are considered malignant. There are just shades of gray in terms of how aggressive they are. Some spread really easily. Others do not. But we consider all of them cancer.
What are the most common symptoms of neuroendocrine tumors?
We tend to see neuroendocrine symptoms in two categories:
Hormonal: These include severe diarrhea, severe gastric ulcers, or uncontrolled blood sugar that respond poorly to treatment. The hormones produced can vary depending on the place in the body where the tumor originates.
Mechanical: These 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 disease. 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.
The second group has no symptoms, and the cancer is detected by chance. Maybe it was picked up during a colonoscopy, or during an X-ray or CT scan for a broken bone.
How are neuroendocrine tumors typically treated?
We have more treatment options today than ever before. They fall into two categories.
The first is local treatments, such as surgery, which focus on the tumor itself. But even when a neuroendocrine tumor has spread, surgery can still be useful in certain circumstances.
Then we get into the systemic treatments, which treat the cancer wherever it is in the entire body. These include conventional chemotherapy, hormone therapy and targeted therapies.
The newest option is a type of systemic radiation called peptide receptor radionuclide therapy, or PRRT. The vast majority of neuroendocrine tumors will 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 tumor progressed by 80%, so it’s a great option for neuroendocrine patients.
There’s no “typical” treatment sequence for neuroendocrine tumors. There are literally hundreds of possibilities. The patient and the care team guide the specific treatment sequence based on their particular clinical situation as it evolves over time.
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 it’s important to stress that whatever diagnosis you may have, it’s not rare or weird to us at MD Anderson. This will not be our first time treating it. 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.
Are there any clinical trials currently available for patients with neuroendocrine tumors?
Yes. One set is looking to build on the success of peptide receptor radionuclide therapy. Another is building on targeted therapies, and a third is focusing on immunotherapy.
Like our patients, we are extremely interested in the promise of immunotherapy to one day help our patients live longer and better lives. We are hard at work in the clinic and the laboratory to figure out the best way forward. The data we have right now suggests it’s not easy to use immunotherapy against neuroendocrine tumors, but we are starting to look 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. Because we believe that the right treatment at the right time by doctors who specialize in treating this complex disease offers patients the most benefit.