What is Intestinal Carcinoid Cancer?
A carcinoid tumor is a specific type of tumor that develops mostly from the cells of the gastrointestinal tract – the parts of your body involved in digestion, like stomach and intestines (in about 55% of the cases). These tumors can also form in other areas such as the lungs, kidneys, or ovaries. However, similar tumors that grow in the pancreas are separate and are known as PNETs. The term “carcinoid” is an old name for these tumors that start in the intestines, and while many doctors are still using the term, it’s worth noting that our understanding of these tumors has improved. Initially, these tumors were named “carcinoid”, a term derived from “Karzinoide”, because they looked similar to carcinomas (a type of cancer) but were considered non-cancerous. Over time, our knowledge and treatment approaches for these necessarily changed as we learned more about them.
What Causes Intestinal Carcinoid Cancer?
The exact cause of NET tumors, a type of growth that occurs in the cells that interact with the nervous system, is unknown. However, there are certain risk factors that could increase the chances of developing such tumors, like having relatives who had these types of tumors or endocrine neoplasia, which is a group of disorders that affect the endocrine system.
These types of tumors have been found in various places in the body, such as the lungs, breathing tubes (bronchi), and parts of the digestive system. They can originate from different parts of the digestive tract. If they start in the foregut (respiratory tract, thymus gland), midgut (parts of the stomach and intestine), or hindgut (lower part of the intestine and rectum), they are called gastrointestinal NETs.
It’s worth mentioning that NETs that originate in the midgut – the middle part of the digestive tract which includes parts of the small intestine, appendix, and the beginning of the large intestine (cecum) – may result in carcinoid syndrome. This is a condition that causes flushing (skin turns red), diarrhea, and difficulty breathing.
Risk Factors and Frequency for Intestinal Carcinoid Cancer
NETs, or neuroendocrine tumors, are not very common. However, there has been an increase in cases of intestinal NETs due to incidental detection during routine imaging tests for other health issues. Typically, small intestinal NETs are mostly found in the ileal region, about 60 cm from the ileocecal valve. Colonic NETs are more typical in older patients and are often found on the right side of the colon, particularly the cecum. Rectal NETs are usually discovered by chance during imaging tests.
There are slight differences in the frequency of these tumors depending on location. Colorectal NETs are seen more often in the Asia/Pacific region, while small intestinal and stomach NETs are more common in Europe. A higher occurrence of intestinal NETs is observed among African Americans compared to Caucasian individuals.
- NETs, though rare, are mainly detected during routine tests for other health issues.
- Small intestinal NETs usually occur 60 cm from the ileocecal valve.
- Colon-based NETs are generally found in older patients and on the right side, specifically the cecum.
- Rectal NETs are usually discovered by chance during imaging tests.
- Colorectal NETs are more common in the Asia/Pacific region, while Europe sees more small intestinal and stomach NETs.
- African-Americans have a higher prevalence of intestinal NETs compared to whites.
- The most common age for gastrointestinal NETs to present is around the 7th decade of life, with a median age of 63 years.
Signs and Symptoms of Intestinal Carcinoid Cancer
Carcinoid syndrome is a condition caused by a tumor, usually in the digestive tract. In some cases, these tumors produce excess hormones, leading to certain symptoms of the syndrome. Sometimes, the signs may be linked to the tumor’s mechanical effect, much like any other gut tumor. This can often lead to occasional or chronic abdominal pain and might even result in a small bowel obstruction.
Most of the time, people with carcinoid tumors don’t exhibit symptoms until the disease has progressed significantly. Often, symptoms appear when the cancer has spread to the liver. Surprisingly, carcinoid syndrome can even be observed in patients with ovarian or kidney tumors, without any spread of the disease.
Patients usually report a range of symptoms including gastrointestinal issues like diarrhea and abdominal cramping. Skin-related symptoms are also common – one of which is flushing caused by the release of histamine from the tumor; occasionally, visible tiny blood vessels or ‘telangiectasias’ are also noted. Other general symptoms may include wheezing due to the constriction of airways triggered by histamine release from the tumor. In some cases, the tumor secretes other hormones like insulin, glucagon, VIP, secretin, or gastrin, which may lead to additional clinical symptoms.
- Occasional or chronic abdominal pain
- Potential small bowel obstruction
- Diarrhea
- Abdominal cramping
- Skin flushing
- Presence of telangiectasias (tiny blood vessels)
- Wheezing
Testing for Intestinal Carcinoid Cancer
Intestinal NETs, or neuroendocrine tumors, are rare and grow slowly. They sometimes make it tricky for doctors to diagnose since they don’t always present obvious symptoms. If a patient experiences unexplained intestinal symptoms, doctors might suspect an intestinal NET. Sometimes, these tumors are found by accident during procedures for other conditions. Once doctors consider the possibility of an intestinal NET, they will conduct further tests to confirm and understand the tumor.
Tests in the Lab
One initial test that could be done if carcinoid syndrome is suspected involves measuring the amount of 5-hydroxy indole acetic acid (5-HIAA) in your urine over a 24 hour period. This test is pretty reliable, with a 90% chance of correctly identifying intestinal carcinoids. However, certain foods or medications that contain serotonin can give a false-positive result. There are also other tests that are used less frequently, such as chromogranin A concentration and measuring the amount of serotonin in your urine.
Imaging
After checking your biochemical markers, your doctor may use imaging to locate the tumor more precisely. This could involve multiple techniques such as CT, MRI, and radio-labelled scans like an octreotide scan and a gallium 68 DOTATE scan.
A triple-phase contrast-enhanced CT scan is the most commonly used technique and is widely available, but it only detects these tumors about 50% of the time. CT scans can struggle to detect smaller tumors (less than 1 cm) and might confuse colorectal adenocarcinomas with colorectal carcinoid tumors due to similarities in appearance. As the tumor grows or advances, the CT scan becomes more helpful, particularly for identifying liver metastases. MRI, in comparison, is the best technique for detecting liver metastasis and can be used instead of a CT scan.
An octreotide scan can detect metastasis (spread of cancer) beyond the abdominal region and is often combined with positron emission tomography (PET) scanning for better detail in the abdominal region. This scan reportedly detects these tumors in a substantial 80% to 90% of patients who don’t have symptoms. However, the use of this scan for regularly checking up on patients with a carcinoid tumor is questionable since the highly sensitive CT scans are readily available.
Treatment Options for Intestinal Carcinoid Cancer
The goal of treating intestinal NETs, which are tumors that form in the cells that interact with the nervous system in the gut, is to manage symptoms, control growth of the tumor, and balance the chemicals in your body. The best way to achieve this is through a combination of various treatment methods, and the choice of treatment depends on how far the disease has progressed.
If the tumor has not spread (metastasized) to other parts of the body, the recommended treatment is surgery to remove the tumor, ensuring that all the diseased tissue is removed. Surgery can potentially cure the condition. However, because these tumors can grow slowly, many patients are already in a more advanced stage of the disease with metastases, particularly in the liver, at the time of their diagnosis.
How much tissue needs to be surgically removed depends on the size, location, and local spread of the tumor. For example, a small tumor can be directly removed, especially if it’s located in the duodenum (initial part of the small intestine) to avoid more extensive surgery. Carcinoids (slow-growing tumors) of the small intestine tend to spread, regardless of their size. Hence, in patients with no evidence of metastases, surgeons remove the section of the small bowel and surrounding tissue where the tumor is located. If the carcinoid tumors are in the large bowel (colon and rectum), they are usually larger and more invasive. Thus, a section of the large bowel and surrounding lymph nodes will need to be removed.
These surgeries can also be performed for symptoms relief when there are complications such as a blocked bowel.
When the disease has spread (metastatic intestinal carcinoid), the first line of defense is a group of drugs called somatostatin analogs. These drugs, which include octreotide and lanreotide, have been shown to be effective in managing symptoms of intestinal carcinoids. However, if the metastatic disease can be removed through surgery and there’s no spread outside the liver, surgery is preferred over medications. The surgical management of tumor-related complications is performed to control these complications.
If patients have worsening symptoms while on somatostatin analogs or cannot tolerate them, Interferon is another treatment option albeit less common due to possible side effects. In addition, therapies targeting specific molecular processes in the cells, for instance mTor inhibitors like everolimus, could be considered.
If the liver is affected by metastasis, surgical removal of the liver tumors can provide symptom relief and improve survival rates. Hence, if a liver metastasis can be removed, this should be incorporated into the surgical treatment plan.
What else can Intestinal Carcinoid Cancer be?
The following are some conditions that could also potentially be diagnosed:
- Crohn’s disease
- Ileus, a condition causing digestive tract disruption
- Small intestinal diverticulosis, where tiny pockets develop in the intestine
- Ulcerative colitis, a long-term inflammation of the colon
What to expect with Intestinal Carcinoid Cancer
Neuroendocrine tumors (NETs) are a type of tumor that grows very slowly. However, like other tumors, they can still cause problems if they grow without control, impacting the working of the digestive system. Complications of advanced intestinal NETs can include blockage of the bowel, rupture of the gut wall, bleeding, and changed gut function.
The outlook for a patient with NETs primarily depends on factors like how advanced the tumor is, where it is in the body, whether it has spread to other parts of the body, if there are other tumors at the same time or that develop later, and the grade or differentiation of the tumor (which refers to how much the cells resemble healthy cells).
However, the overall outlook for intestinal carcinoid tumors, a type of NET, is generally positive. High survival rates have been reported for patients with intestinal NETs, including those with tumors that have spread to distant parts of the body. The survival rate over 5 years can range between 40% to 85%.
