The small intestine is part of the gastrointestinal (GI) tract, also known as the digestive tract. The GI tract processes food for energy and nutrients and rids the body of solid waste. It is the longest section of the GI tract (about 6 meters in length) and is called the small intestine because of its smaller caliber. Small intestine cancer is less common than most other types of gastrointestinal cancer (cancers of the colon, rectum, stomach and esophagus).
Most small intestine cancers (especially adenocarcinomas) develop in the duodenum – the first section of the intestine, which is only about 30 centimeters long. Small intestine cancer is a rare disease in which cells in the tissue of the intestine change, grow out of control and form a tumor.
Among its risk factors are age (with a higher incidence in people over 60 years of age), smoking and alcohol use, diets rich in red meat and salty or smoked foods (such as sausages), untreated celiac disease (eating gluten, in these cases, causes the body’s immune system to attack the lining of the intestine), previous history of colon cancer, Crohn’s disease, MUTYH-associated polyposis or cystic fibrosis (CF), and having risk of inherited conditions and syndromes such as familial adenomatous polyposis (FAP), Lynch syndrome and Peutz-Jeghers syndrome (PJS).
Types of cancer in the small intestine
The small intestine is made up of different types of cells and therefore different types of cancer can originate in that area. The following are the four main types of small intestine cancer:
- Adenocarcinomas – starts in the gland cells that line the interior of the intestine and account for 30 to 40% of cases. At first, it may look like a small, non-malignant tumor called a polyp, but over time it develops into cancer;
- Carcinoid tumors – a type of neuroendocrine tumor (NET) that tends to grow slowly. It’s the most common type of small intestine tumor. It usually appears in the lower part of the small intestine and it can also affect the appendix or rectum;
- Lymphoma – this disease starts in cells of the immune system called lymphocytes. Lymphomas can start in almost any part of the body, including the small intestine. People who develop this type of cancer tend to have the body’s natural defense system weakened, unable to fight infections and diseases as it should;
- Sarcomas (GIST) – are cancers that start in connective tissues, such as muscles. The most common sarcoma of the intestine is gastrointestinal stromal tumor (GIST).
Small intestine cancer symptoms
Symptoms of small intestine tumors include:
- Abdominal mass;
- Abdominal pain;
- Weight loss for no apparent reason;
In some cases, the first symptom is pain in the stomach area. The increase in tumor mass can partially block the passage of digested food, which intensifies the pain. Complete blockage of the intestine causes vomiting, distention, and severe pain in the abdomen.
Small intestine cancer diagnosis
Early detection of cancer often allows for more treatment options. As it is a rare cancer, screening tests are not performed to detect the neoplasm in asymptomatic people.
Regular checkups are recommended for people with certain inherited genetic syndromes who have an increased risk of cancer of the small intestine, especially the duodenum.
The most commonly used diagnostic tests for small intestine cancer are:
- Barium contrast X-rays – a barium solution is used to fill the GI tract, allowing the tumors to become more visible. It’s not the best exam; however, it’s cheaper, making it more accessible;
- Upper GI series – this exam is used to assess the esophagus, stomach, and the first part of the small intestine (duodenum). When ingested, barium contrast covers the lining of the esophagus, stomach, and small intestine. As X-rays do not pass through barium, it is possible to delineate abnormalities of larger volume in the lining of these organs;
- Enteroclysis – liquid barium is inserted into the small intestine through a tube that is inserted through the mouth, through the stomach and into the beginning of the small intestine, along with a substance that dilates the intestine. This exam allows doctors to obtain clearer images of the interior portion of the small intestine;
- Capsule endoscopy – allows the assessment of the lining of the middle part of the GI tract, which includes the three portions of the small intestine, a part of the intestine that cannot be reached by endoscopy or colonoscopy. The patient swallows a capsule containing a micro camera, a light source and a microscopic transmitter, which makes high-resolution images of segments of the digestive tract. Images are transmitted electronically to a device worn around the patient’s waist.
The capsule is propelled by peristaltic movements through the digestive tract and naturally eliminated by defecation. This test does not require sedation and the patient returns to normal daily activities as the capsule travels through the GI tract;
- Computed tomography – diagnostic imaging technique that uses X-radiation at a higher dose to visualize body regions. By computerized techniques, the patient’s image is divided into small pieces for better evaluation. The equipment has an examination table that slides into the equipment, which is open, not causing the feeling of claustrophobia. This exam can be performed with or without the use of contrast and can be used to precisely guide the placement of a biopsy needle in an area where cancer is suspected. It is also often used to examine the chest and abdomen to check if the disease has spread to the lymph nodes or other organs such as the liver.
- Nuclear medicine exams – PET-CT is a nuclear medicine technique that combines the tomography exam with the infusion of a radiotracer, a substance labeled with a low-radiation component. This allows, in addition to the image produced, to carry out a functional assessment, showing where the radiotracer is most concentrated. There are different types of bookmarks. On FDG PET, glucose is labeled to indicate the areas with the highest metabolism, since neoplasms have intense glucose consumption. This exam is requested mainly in the case of lymphomas. In the case of carcinoid tumors, in addition to PET with FDG, PET scans with gallium and Octreoscan may also be requested, which is performed with radiotracers that bind to somatostatin receptors and help establish the treatment protocol for the disease;
- Upper digestive endoscopy – allows the doctor to examine the inner lining of the esophagus, stomach, and the first part of the small intestine (duodenum). During the examination, tissue samples may be obtained from the suspicious areas, which will later be sent to an analysis laboratory. Resection of polyps by examination is also important to prevent further transformation into a malignant disease;
- Colonoscopy – uses a special endoscope inserted through the anus into the colon. The doctor will be able to see the lining of the entire rectum and colon, as well as the final end of the small intestine. It is also possible to remove polyps and material for pathology examination;
- Double-balloon enteroscopy – is an endoscopic examination of the deep parts of the small intestine. This exam uses a sophisticated technology: in addition to using a video-endoscopic system specifically designed to examine the small intestine, a balloon is attached to one end of the device and introduced into the endoscope and another balloon is attached to the other end, and both are used together. The balloons are inflated and deflated safely and effectively, by means of an air pump that, by tapping, allows a strict control of the pressure inside them. The examination can be performed orally or through the rectum;
- Laboratory tests – in the complete blood count test, the rate of red blood cells is investigated, that is, if the patient has anemia. In the biochemical examination of the blood, changes in liver enzymes may be evaluated, which may indicate the presence of metastases in this organ;
- Biopsy – the only way to confirm the presence of cancer is to have a biopsy. In this procedure, a tissue sample from the suspected area is removed and sent for analysis by a pathologist. One of the ways to obtain a sample of an intestinal tumor is through an endoscope. At the end of the equipment, in addition to the lens and a light, there is a tool to remove the tissue. In some patients whose tumors cannot be reached with the endoscope, a surgical biopsy is required;
- Laboratory testing of biopsy specimens – in immunohistochemistry testing, a part of the specimen is treated with synthetic antibodies that bind only to a certain protein on the cells. Antibodies cause color changes if the protein is present, and they can be seen under a microscope. This test is important to determine the histological type of the patient’s cancer. If GIST is suspected, for example, KIT (also known as CD117) and DOG1 are tested. Most GIST cells have these proteins, but cells from most other cancers do not – so this type of test is important in defining the type of tumor. Other proteins may also be tested, helping the pathologist to define the type of disease.
Treatment for small intestine cancer depends on the type of cancer, whether or not the tumor can be removed completely with surgery, and whether the disease is still localized or has spread to other organs.
Treatment for adenocarcinoma in the small intestine
- Surgery – when the cancer is just at or close to where it started and has not spread, surgery is usually done to try to remove the entire tumor. If the cancer has spread too far to be removed completely, surgery may be done to help prevent or alleviate issues caused by the tumor, which often grows large enough to block the bowel. The type of operation will depend on a number of factors, including the size and location of the tumor and whether the person has any health problems;
- Segmental resection – this operation removes the segment of bowel that contains the tumor, as well as some of the normal tissue around the tumor. Some nearby tissue containing lymph nodes is also removed. This procedure can be done by a cut in the abdomen – open surgery – or, for some smaller tumors, by laparoscopic surgery, in which an operation is done through several small cuts with long, thin surgical instruments, including a camera for video assistance;
- Pancreaticoduodenectomy – can be used to treat cancer of the duodenum (the first part of the small intestine), although it is most often used to treat pancreatic cancer. This surgery removes the duodenum, part of the pancreas, part of the stomach, and nearby lymph nodes. The gallbladder and part of the common bile duct are also removed. The remaining bile duct is connected to the small intestine so that bile from the liver enters the small intestine;
- Palliative surgery – if the cancer cannot be removed completely, surgery may still be a good option to prevent or alleviate some symptoms. In this case, a palliative surgery can be performed to relieve a blocked intestine, reduce pain, nausea and vomiting and allow the patient to eat normally, for example;
- Chemotherapy – chemotherapeutics attack cells during cell division, mainly affecting rapidly replicating cells such as cancer cells. They enter the bloodstream and can reach cancer cells anywhere in the body. They can be used when the cancer has spread to other parts of the body or after the tumor is surgically removed to lessen the chance that the cancer will return. This is the main treatment in the case of lymphomas. Chemotherapy drugs kill cancer cells, but they also damage some normal cells, which can cause side effects. The main ones are nausea and vomiting, loss of appetite, hair loss, canker sores and diarrhea;
- Radiotherapy – uses high-energy radiation to kill cancer cells. It may be an option when the cancer cannot be removed completely with surgery and is causing problems such as pain or bleeding in the intestines. External beam radiation therapy is the most commonly used type of radiation for cancer of the small intestine. For this treatment, beams of radiation are directed at the tumor from a machine outside the body. The main side effects of radiation therapy on the intestines include fatigue, nausea and vomiting, diarrhea, and changes in the skin where the radiation beams have passed, such as mild redness, blistering, and peeling.
Treatment for small intestine carcinoid tumors
Many gastrointestinal (GI) carcinoid tumors can also be cured by surgery alone. The type of operation will depend on several factors, including the size and location of the tumor, whether the person has other serious illnesses, and whether the tumor is causing carcinoid syndrome.
Various types of operations can be used to treat GI carcinoid tumors and, in some cases, are similar to those used in adenocarcinoma. The following are the specific procedures to treat this condition:
- Surgery on carcinoid tumors that have affected the liver – when there are only one or two tumors in the liver, they can be removed with surgery. If there are more than a few liver tumors (or if the patient is too sick to withstand surgery), other techniques may be used;
- Liver resection – in this operation, one or more parts of the liver that contain cancerous areas are removed. If it is not possible to remove all areas of cancer, surgery may be done to remove as much of the tumor as possible to help reduce the symptoms of carcinoid syndrome. This procedure is called cytoreductive surgery;
- Ablation – Ablation techniques destroy tumors without removing them. They are usually best for tumors no more than 2 cm in diameter and are made using interventional radiology techniques;
- Chemotherapy – is usually only used for tumors that have spread to other organs, are causing severe symptoms, have not responded to other medications, or are high-grade tumors. Other medications that can be used are small molecules capable of interfering with intracellular metabolism;
- Nuclear medicine treatments – treatments made with radioactive compounds coupled to specific molecules and injected into the patient;
- Radiotherapy – may be an option for those who cannot have surgery for some reason. It can also be given after the surgical procedure is done in some cases, if there is a chance that part of the tumor has not been removed. Radiation therapy can also be used to help relieve symptoms such as pain if the cancer has spread to the bones or other areas.
Treatment for sarcoma-like small bowel cancer (GISTs)
- Surgery – if the tumor is small, it can usually be removed along with a small area of normal tissue around it. This is done through a cut (incision) in the skin. Unlike many other types of cancer, GISTs almost never spread to the lymph nodes, which do not need to be removed. If the tumor is large or develops in other organs, the surgeon may still be able to remove it completely, and it is often necessary to remove parts of organs (such as a section of the intestines). Another option for tumors that are large or that have grown in nearby areas may be to take the target drug first. This is called neoadjuvant treatment, and it can often shrink the tumor, making it easier to remove with surgery.
- Targeted therapy – some drugs can target certain proteins on gastrointestinal stromal tumor (GIST) cells that help them divide and grow. These targeted drugs – also called targeted or precision therapy – are often very helpful in treating GISTs. They work differently from conventional chemotherapy drugs, which are generally not helpful in these cases;
- Radiotherapy – Radiotherapy is the use of high-energy X-rays (or particles) to kill cancer cells. Radiation is not very helpful in treating GIST, so it is not used often. But it can sometimes relieve symptoms like bone pain.
Treatment for small intestine lymphoma
Depending on the type and stage (extent) of the lymphoma and other factors, treatment options for people with the disease also include procedures common to other types of small intestine cancer, such as targeted therapy, chemotherapy, and radiation. Surgery is often used to obtain a biopsy sample to diagnose and classify lymphoma, but it is rarely used as a form of treatment.
- Immunotherapy – Immunotherapy is treatment that stimulates the patient’s own immune system to kill lymphoma cells or slow their growth. Immunotherapy drugs prevent the cancer from becoming camouflaged and not being detected by the immune system;
- Antibodies – Antibodies are proteins produced by the immune system to help fight infections. Laboratory-produced versions, called monoclonal antibodies, can be designed to attack a specific target, such as a substance on the surface of lymphocytes (the cells in which lymphomas begin). Several monoclonal antibodies are now used to treat non-Hodgkin’s lymphoma (NHL);
- High-dose chemotherapy and stem cell transplant – a stem cell transplant (also known as a bone marrow transplant) allows doctors to give higher doses of chemotherapy, sometimes along with radiation therapy. Doses of chemotherapy drugs are usually limited by the side effects caused by these drugs. Higher doses cannot be used, even though they might kill more cancer cells, because they would severely damage the bone marrow, where new blood cells are made. But with a stem cell transplant, doctors can give high doses of chemotherapy because the patient will receive a blood-forming stem cell transplant to restore the bone marrow later. Stem cell transplants are sometimes used to treat lymphoma patients who are in remission or who have relapsed during or after treatment.
The following are the two main types of stem cell transplants (SCTs):
- Autologous stem cell transplantation – the patient’s own stem cells are used, which are collected several times in the weeks prior to treatment. The cells are frozen and stored while the person receives treatment (chemotherapy and/or high-dose radiation) and then returned to the patient’s blood through an IV (catheter in a vein);
- Allogeneic stem cell transplantation – the stem cells come from someone else (a donor). The donor is usually a brother or sister, although the source could be an unrelated donor or cord blood unit.
It is not known for sure why people develop cancer of the small intestine, but several factors can increase the risk of the disease developing, as mentioned at the beginning of this article. Avoiding them, when they are controllable (bad eating habits and smoking, for example), is a way to prevent the disease. When they are not preventable, such as hereditary conditions and syndromes, keeping them monitored by periodic exams can be a way to detect cancer in its early stages and increase the chance of cure.