Cancer can arise anywhere in the body where living tissue exists. It can also spread to any site away from where it originates. Some organs are more prone to cancers especially when there are certain risk factors present. The lungs, breasts, prostate, colon and rectum are the most commonly affect areas. Small bowel (small intestine) cancer is one of the rare types and for this reason many people do not know much about it. However, it is closely linked to colon cancer in the types of tumors and due to the coiling nature of the bowels, colon cancer could directly spread to the small intestines.
What is small bowel cancer?
Small bowel cancer is a malignant growth in the small intestine. Sometimes the term bowel cancer is used broadly which refer to small intestine or large intestine cancer. Since the latter is far more common, the term bowel cancer usually refers to cancerous tumors in the large intestine and specifically within the colon. However, small bowel cancer clearly indicates a malignancy in the small intestine. Overall it is a rare type of cancer and accounts for about 2% of gastrointestinal cancers.
Research into various aspects of small bowel cancer and its management has been limited by the rarity of this type of tumor. Only about 5,000 cases a year are diagnosed in the United States. Men are at a slightly higher risk of developing small bowel cancer than women. It is more commonly seen around the age of 60 years. Often the disease is diagnosed late due to lack of symptoms in the early stages and the vague nature of these symptoms once it arises.
Causes of Small Intestine Cancer
Tumors are abnormal growths which can be either cancerous (malignant) or non-cancerous (benign). Normally the multiplication of cells and its growth pattern are controlled by a number of different factors like the genetic material (DNA) within cells. When the DNA is damaged or defective, cells can multiply rapidly and may be abnormal in structure. These cancer cells may invade and destroy healthy tissue. It could also detach from the original site where it arose and spread to other sites. This is known as metastatic spread.
There are different types of cancerous tumors that may arise in the small intestine. These types are classified by the type of cell it originates from as well as any substances that may be secreted by the tumor.
Most small bowel malignancies are adenocarcinomas. These adenocarcinomas in the small bowel are similar to adenocarcinomas in the large intestine. It usually starts from a tumor known as an adenoma. Although adenomas are benign tumors, it can become malignant. About half of all small bowel adenocarcinomas occur in the duodenum, which is the first part of the small intestine. Approximately 30% occur in the jejunum and 20% in the ileum, the last of the small intestine which then connects with the large intestine.
Certain risk factor increase the likelihood of small bowel cancer developing. It does not always mean that a person with one or more of these risk factors will definitely develop cancer.
- Genetic factors like familial adenomatous polyposis.
- Diet particularly red meat, smoked and salt-cured meats.
- Crohn’s disease (inflammatory bowel disease)
- Lifestyle factors like excessive alcohol consumption and tobacco use.
- Celiac disease (nontropical sprue)
Signs and Symptoms
As with most cancers, the early stages of small bowel cancer are usually asymptomatic. This means that there is little to no symptoms present. Most patients will experience symptoms in the advanced stages of the disease although the diagnosis is often delayed at this point due to non-specific nature of the symptoms. The more common symptoms are:
- Intestinal obstruction
- Abdominal pain (late symptom)
Unintentional weight loss may even present but this is usually in the advanced stages. Weakness and fatigue are also frequently seen but it is non-specific and sometimes may be a consequence of chemotherapy and due to the tumor itself. Bleeding in the bowels eventually arises as well but its not as common as the symptoms above. Complications may present with a distended abdomen, tenderness and jaundice. In rare instances the intestine may be perforate (torn) and the intestinal contents can spill into the abdominal cavity to cause peritonitis.
The small intestine measure between 25 to 30 feet and it is often difficult to identify the site of a bowel problem without specialized diagnostic investigations. Imaging studies such as a CT scan or endoscopic investigation are helpful for identifying the location of the tumor. A biopsy is then done to verify that the tissue sample is a malignancy as well as the type of tumor. The tumor has to be graded and staging will be done to verify if there is any spread of the cancer cells. Both measures can help to determine the course of treatment.
The 5 year survival rate of small bowel cancer varies among the different types. It may be about 30% to 35% for adenocarcinomas and about 25% for sarcomas. However, it is not just the type that will determine the survival. Various other factors have to be considered as well. Generally the earlier a cancer is detected, the better the prognosis.
The treatment of small bowel cancer may require medication and/or surgery. These measures are not significantly different as the treatment for other cancers. Where possible the section of the bowel where the cancer is present should be surgically removed. The two ends of the bowels can then be joined together. Chemotherapy may be administered to help destroy cancer cells. Surgery is considered to be curative when the entire tumor can be removed without any remaining traces.
Sometimes surgery and medication are utilized for advanced cases where the cancer cannot be cured or put into remission. In these cases the treatment is intended to provide symptomatic relief. Other surgical procedures may also need to be done if there are complications. Bile duct stenting is necessary when the tumor in the duodenal area presses against the bile duct. A blood transfusion may be necessary when there is significant blood loss from a bleeding tumor leading to anemia.