What is Small Bowel Cancer?
Small bowel cancer refers to a range of harmful growths that can occur throughout the small intestine. The small intestine is the part of the digestive system that connects the stomach and the large intestine. It consists of three parts: the duodenum, jejunum, and ileum. Both non-harmful and harmful growths can appear anywhere in the small intestine, but they are quite rare compared to those found in other parts of the digestive system.
This summary will discuss the main characteristics, how it’s diagnosed, treatment options, and what to expect for harmful growths. Often, these growths can cause various generic symptoms, which may lead to delays in diagnosis and treatment. Regular symptoms include stomach pain, loss of appetite, gastrointestinal bleeding, and weight loss. In more serious cases, symptoms could include a tear in the intestine, blockage of the small intestine, or a blockage causing yellowing of the skin and eyes. The method for diagnosis may vary based on the exact location of the growth and is typically a combination of laboratory tests, imaging scans, and an internal examination of the digestive tract.
The types of dangerous growths usually found in the small intestine are lymphomas, neuroendocrine tumors (also known as carcinoids), adenocarcinomas, and stromal tumors. Meanwhile, adenomas are the most common non-harmful tumors found in the small intestine, but other non-dangerous conditions involving the blood vessels, fat, and lymph tissue can also affect the small intestine. These conditions could include fibromas, lipomas, hemangiomas, lymphangiomas, and neurofibromas.
While harmful small intestine tumors are rare, with only around 10,000 new cases diagnosed recently in the United States, the most common types in order of decreasing occurrence are adenocarcinoma, carcinoid tumor, and lymphoma. Some tumors previously classified as leiomyomas and leiomyosarcoma are now recognized as the most frequent type of mesenchymal tumors seen in the small intestine, called Gastrointestinal stromal tumors (GISTs). It should also be noted that other kinds of cancer, like melanoma, could spread to the small intestine, or there could be an invasion from a nearby organ.
What Causes Small Bowel Cancer?
Tumors in the small intestine may be caused by several factors including diet, particularly red meat and smoked or cured foods. Other risk factors include conditions that cause chronic inflammation in the intestines such as Crohn’s disease, immune disorders that disrupt food absorption like celiac disease, and hereditary conditions that make you more likely to get intestinal cancer, for instance, HNPCC, FAP, or Peutz-Jeghers syndrome.
Research has shown that cancer in certain parts of the small intestine is more common than in others. For example, adenocarcinoma is most often found in the duodenum, a section of the small intestine, whereas neuroendocrine tumors frequently appear in the ileum, another part of the small intestine. Sarcomas and lymphomas, two other types of cancer, seem to occur at equal rates throughout the small intestine.
Whatever the type of small bowel cancer it is, each has its own set of hereditary conditions that could increase the risk. These cancers depend on genetic mutations which lead to the transformation of cells into cancer cells.
Potential types involve sarcomas – which are usually leiomyosarcoma and primarily originate from muscle tissue (common in the ileum); gastrointestinal stromal tumors (or GIST) – which arise from interstitial cells of Cajal and are considered soft tissue sarcomas; adenocarcinoma – which typically starts from the glandular cells of the small intestine; neuroendocrine tumors (or carcinoid tumors) – which come from hormone-producing cells and so are often linked with secretory cells that cause particular clinical features; and lymphoma – which comes from the lymphatic system associated with the small intestine.
Patients with pre-existing conditions may also have a predisposition to certain types of small bowel cancers. Celiac disease increases the risk of high-grade lymphomas of the small bowel, specifically, non-Hodgkin lymphoma subtypes. People with Crohn’s disease can have an up to 60-fold increased risk for developing adenocarcinoma of the small bowel. Furthermore, hereditary cancer syndromes that raise the risk of colon cancer often also increase the risk for small bowel cancer. These include FAP, HNPCC (also known as Lynch syndrome), Peutz-Jeghers syndrome, MUTYH-associated polyposis, and cystic fibrosis.
The understanding of how adenocarcinomas and GISTs develop is ongoing research. Yet, much less is known about the development of other small-intestinal tumors. Adenocarcinoma of the small intestine seems to develop in a similar way to colorectal adenocarcinoma, with sequential genetic abnormalities. It’s also important to note that people with hereditary polyposis disorders are at an increased risk of developing these types of cancer. Moreover, a certain type of cancerous tumor (GIST tumors) have been seen to contain mutations with a gain of function tendency of a gene called KIT, which is key in unopposed cellular growth. The interstitial cells of Cajal play a vital role in the development of GISTs, and the KIT receptor is present in most GIST tumors.
Risk Factors and Frequency for Small Bowel Cancer
Small-intestinal cancers, also known as malignancies, are most frequently diagnosed in people in their 50s or 60s. This condition is typically more advanced when first identified, especially compared to colorectal cancer. In the United States, it isn’t very common, making up just 3 to 5% of all gastrointestinal cancers. That’s pretty low, especially considering the small intestine makes up about 90% of your gastrointestinal tract’s surface area. However, colon cancer is the third most common cancer-related cause of death in the US. Small-intestinal cancer can appear in several forms, and the exact patterns and frequency can vary for each type.
- Sarcoma, most commonly GIST tumors, are found frequently in people around 65, with more men having it than women. Overall, however, sarcomas are most commonly found in children.
- Adenocarcinomas usually appear in men aged 50 to 70. Certain conditions, like Inflammatory Bowel Disease (especially Crohn’s Disease) and specific inherited cancer syndromes like FAP and HNPCC, increase the risk and may lead to diagnosis at a younger age.
- Neuroendocrine Tumors generally occur in patients aged 50 to 70, and most commonly found in those over age 65. These tumors affect both males and females evenly in the small intestine and rectum. However, when found in the stomach, appendix, or colon, women are affected more commonly than men.
- Lymphoma makes up about 9 to 10% of all cancers in the gastrointestinal tract and typically appears in individuals between the ages of 60 and 70, with a stronger prevalence in men (60% vs. 40%).
Signs and Symptoms of Small Bowel Cancer
Small bowel cancers, for the most part, show similar symptoms. However, neuroendocrine tumors, a particular type of small bowel cancer, can produce unique symptoms based on what the cancer cells are secreting. The most common symptoms of small bowel cancer include occasional stomach pain, unexplained weight loss, and gastrointestinal bleeding. The stomach pain usually comes and goes and can be associated with nausea and vomiting. Bigger cancerous growths can lead to serious issues like blockage or a hole (perforation) in the small bowel. Blockage is more common than perforation. These symptoms often lead to delayed diagnosis because they’re not specific to this type of cancer, and the physical examination findings can vary depending on the stage of the disease and the symptoms displayed.
When neuroendocrine tumors have spread to the liver, they can cause a variety of symptoms due to the substances the tumor secretes. This is why testing for certain biomarkers is included in the diagnosis process to confirm what’s causing the symptoms. The most common symptoms of carcinoid syndrome, associated with neuroendocrine tumors, are skin flushing, diarrhea, enlargement of small blood vessels on the skin (venous telangiectasias), and recurring breathing problems due to constricted airways (bronchospasms).
- Occasional stomach pain
- Unexplained weight loss
- Gastrointestinal bleeding
- Nausea and vomiting (in some cases)
- Bowel obstruction or perforation (in extreme cases of larger growths)
- For neuroendocrine tumors that spread to the liver: skin flushing, diarrhea, venous telangiectasias, and recurring bronchospasms.
Testing for Small Bowel Cancer
If doctors suspect small bowel cancer, they use several methods to diagnose it, such as lab tests, imaging scans, and endoscopy. The symptoms of this cancer can often be nonspecific, meaning they may resemble those of other conditions or diseases. Sometimes, this makes it quite challenging and time-consuming to diagnose small bowel cancer precisely.
At the start, doctors usually conduct blood tests to check for abnormal cell counts, any unusual chemical reactions, and to assess how well the liver is functioning. In some cases, patients may have anemia due to bleeding that’s not visible to the naked eye. For neuroendocrine tumors, which are a type of small bowel cancer, doctors would further run tests to check certain chemical markers in the body.
Imaging tests are usually performed to get a clearer picture of what’s happening inside the body. The commonly used imaging scans include the CT scan which is useful for finding abnormalities in about 70-80% of patients. However, the effectiveness of the CT scan can vary based on the exact location of the cancer. Other imaging techniques like an upper GI series and enteroclysis involve using barium to outline the esophagus, stomach, and small intestines. These techniques, however, can’t detect smaller cancers or understand the stage of the cancer.
Endoscopies are another diagnostic option that allows doctors to see the inside of your body. They can be useful in identifying more hidden or distal lesions which are not detectable by other imaging methods. However, the downside is that the endoscopies don’t allow doctors to take a tissue sample for further examination.
If a patient is believed to have small bowel adenocarcinoma, a specific type of small bowel cancer, the National Comprehensive Cancer Network (NCCN) suggests a detailed evaluation. It may involve further lab and imaging tests, as well as checking for specific tumor markers. Doctors may also conduct Esophagogastroduodenoscopy (EGD) and endoscopic ultrasound (EUS) to stage the cancer, distinguish it from other nearby tumors, and collect tissue samples. In certain complicated cases, additional endoscopic methods are used, and surgical intervention may be considered.
The last step involves examining the size and spread of the tumor using either a CT scan or MRI. In some specific instances, doctors may perform a PET-CT scan to check for the spread of cancer.
Treatment Options for Small Bowel Cancer
Small bowel sarcomas include types of tumors known as GIST and non-GIST. The treatment for these depends on the exact type found. In the case of GIST tumors, they often show active mutations in a gene known as the KIT proto-oncogene, so treatments are developed to target this. KIT inhibitors, in particular a drug called Imatinib, are usually the first choice. Unlike other types of cancer, GIST and non-GIST tumors rarely spread to the lymph nodes, so it is not necessary to remove these nodes during surgery. Instead, the focus is on removing the main tumor and making sure none of the tumorous tissue gets accidentally spread during the operation.
Small bowel adenocarcinoma is a type of cancer that is typically treated by taking out a large segment of the small bowel during surgery. The surrounding tissue, or the mesentery, is also removed when taking out the tumor. Lymph nodes around the tumor are also usually taken out during surgery, as this can help determine if further treatment with chemotherapy is necessary. If the tumor is larger and involves the first two parts of the small bowel, a complex surgical procedure known as a Whipple procedure may be considered.
Neuroendocrine tumors often appear in the jejunum and ileum sections of the small bowel. These tumors grow slowly and are usually well differentiable from normal tissue. However, they can spread to other parts of the body. Surgery to remove the tumor, the nearby mesentery, and lymph nodes is usually recommended for patients where the disease is localized. For patients with advanced disease and symptoms consistent with a condition called carcinoid syndrome, surgery is unlikely to be a cure and is generally reserved for reducing symptoms. Chemotherapy is usually suggested after surgery. However, if a patient has not started chemotherapy and begins to show symptoms of bowel obstruction, treating the obstruction becomes the priority.
Finally, most lymphomas in the gastrointestinal tract are a type called non-Hodgkin lymphoma. Although these tumors are usually managed with surgery and potentially chemotherapy depending on the specific type of lymphoma, radiation therapy is not typically used due to the risk of complications associated with radiation in the abdominal cavity. Research has not proven that the benefit of such radiation therapy outweighs the long-term risks.
What else can Small Bowel Cancer be?
The symptoms of small bowel cancers can often be unclear and may include long-term or reoccurring stomach pain, feeling sick, vomiting, weight loss, or signs related to further complications from the cancer such as bleeding in the gastrointestinal system or blocked bowel symptoms. Patients with a type of tumor known as NETs might display more distinct symptoms, which could help healthcare professionals identify the condition earlier. This is mainly because some NET tumors are linked with a condition called carcinoid syndrome, causing a range of symptoms that are typically not associated with small bowel cancers. So, it’s very important for doctors to consider other conditions that can show similar symptoms. These can include conditions like irritable bowel syndrome, peptic ulcer disease, esophagitis, inflammatory bowel disease, lipomas, hemangiomas, functional abdominal pain, and adenomas.
Surgical Treatment of Small Bowel Cancer
Surgical treatment is the recommended approach for addressing adenocarcinoma of the small bowel that is either localized or locoregional. This involves surgically removing the tumor and the nearby lymph nodes. During this procedure, it’s vital to carefully determine the extent of the disease, especially in the mesentery (the tissues that attach our intestines to the abdominal wall), omentum (a large fatty structure that covers the abdominal organs), and peritoneum (the lining of the abdomen). The specifics of the surgery depend on the exact location of the tumor in the intestine.
For example, if the cancer is located in the jejunum (the middle section of the small intestine) or the ileum (the last section of the small intestine), a surgical procedure called a ‘segmentectomy’ may be performed, which involves removing the diseased portion of the intestine. If the adenocarcinoma is near the start of the small intestine or involves the pancreatic duct, a more involved procedure, called a ‘pancreaticoduodenectomy’ or ‘Whipple procedure’, may be required. ‘Laparoscopic Whipple procedure’ can be performed on selected patients but should be done in specialized centers due to its technical complexity.
When the tumor is less than 2 cm in size, surgeons may opt for a simple segmentectomy, even if it’s difficult to determine the condition of the nearby lymph nodes. To understand how advanced the cancer is, at least eight lymph nodes should be evaluated.
About one-third of individuals with small bowel adenocarcinoma have disease spread beyond the bowel, with many having it in their peritoneal cavity or liver. Survival rates for this group are startlingly low, with only about half surviving for five years. For stage IV patients with resectable disease, surgery can still play a role in managing the tumors present in these locations. It’s important to note, however, that survival rate is significantly lower among patients with duodenal adenocarcinoma, as compared to other types of small bowel adenocarcinoma.
Up to half of the diagnosed individuals will have a condition called ‘peritoneal carcinomatosis’, which is a spread of the cancer to the peritoneum. In such cases, if the spread is unresectable, chemotherapy may be used to help manage symptoms. However, if it is resectable, surgery can be an option. Currently, a procedure called ‘hyperthermic intraperitoneal chemotherapy’ for managing small bowel adenocarcinoma with peritoneal carcinomatosis is not commonly recommended due to a lack of strong supportive evidence.
What to expect with Small Bowel Cancer
The outlook for sarcoma, a type of cancer, depends heavily on factors such as where the tumor is located, its size, and whether it can be removed through surgery. If the tumor can be removed, the average five-year survival rate is around 80%.
Adenocarcinoma, another type of cancer, has a prognosis that largely depends on its stage at diagnosis. Generally, adenocarcinoma found in the small intestine tends to be more deadly than similar staged colon cancers. The involvement of lymph nodes greatly affects prognosis, with the presence of disease in the nodes reducing the five-year survival rate by about 40%. If the cancer has spread to distant parts of the body, the prognosis worsens significantly. Other crucial factors influencing prognosis include the specific site of the cancer within the small intestine, certain features of the tumor, the number of lymph nodes examined, and underlying conditions like inflammatory bowel disease and celiac disease.
Small bowel adenocarcinoma often brings complications such as obstruction of the duodenum or abdominal cramps, while some patients may face hidden gastrointestinal bleeding.
Neuroendocrine tumors are a bit more complicated when it comes to predicting outcomes, as prognosis depends on elements like the size of the tumor, what it secretes, if there are symptoms of carcinoid syndrome, and the extent of lymph node involvement and metastasis. Generally, tumors with no signs of carcinoid syndrome have high survival rates, sometimes up to 90%.
For lymphoma, the surgical removal of the tumor generally leads to high survival rates. However, the overall prognosis can vary due to high recurrence rates. The prognosis and follow-up plans are typically guided by the Ann Arbor staging scale, which assesses the extent of lymphoma in one’s body.
Possible Complications When Diagnosed with Small Bowel Cancer
If the diagnosis of small bowel cancer is delayed, patients frequently show up with complications at the later stages of the disease. These complications may comprise:
- Bleeding in the upper and lower parts of the digestive tract
- Obstruction in the small bowel
- Perforation, or tear, in the small bowel
- Peritonitis, which is an inflammation of the thin tissue that lines the inside of the abdominal wall and covers most of the abdominal organs
Preventing Small Bowel Cancer
Small bowel cancer is a group of uncommon malignant diseases that can be found anywhere in the small bowel. Medical practitioners should keep it in mind when investigating unexplained gastrointestinal symptoms, as it can lead to earlier detection and diagnosis. Patients should also be informed about significant warning signs or complications that may occur once the disease has been diagnosed. Depending on the seriousness of the disease, support services like palliative care teams and support groups should be involved for comforting the patient.
