Small intestine

The small intestine is part of the gastrointestinal tract (GI), also known as the digestive tract. The GI tract processes food to obtain energy and nutrients and rid the body of solid waste. It is the longest section of the GI tract (about 6 meters long) and is called the small intestine because it has a smaller diameter. Tumors in the small intestine are less common than most other types of gastrointestinal cancer (colon, rectum, stomach, and esophagus cancer).

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 the cells of the intestinal tissue change, grow uncontrollably, and form a tumor.

Among its risk factors are age (it tends to occur more frequently in people over 60), smoking and alcohol use, diets high in red meat and salty or smoked foods (such as processed meats), uncontrolled celiac disease (eating gluten in these cases causes the body’s immune system to attack the lining of the intestine), having had colon cancer, having Crohn’s disease, MUTYH-associated polyposis, or cystic fibrosis, and having a risk of hereditary 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 composed of different types of cells, and therefore, different types of cancer can begin there. The four main types of small intestine cancer are:

• Adenocarcinomas – begin in the glandular cells that line the inside of the intestine and account for 30% to 40% of cases. Initially, it may appear as a small noncancerous tumor called a polyp, but over time, it develops into cancer;

• Carcinoid tumors – are a type of neuroendocrine tumor (NET) and tend to grow slowly. They are the most common type of small intestine tumor. They usually arise in the lower part of the small intestine. They can also affect the appendix or rectum;

• Lymphoma – this disease begins in the immune system cells called lymphocytes. Lymphomas can start in almost any part of the body, including the small intestine. People who develop this type of cancer often have a weakened natural defense system, unable to fight infections and diseases as it should;

• Sarcomas (GIST) – are cancers that begin in connective tissues, such as muscles. The most common sarcoma of the intestine is gastrointestinal stromal tumor (GIST).

Symptoms of small intestine cancer

The symptoms of small intestine tumors include:

• Appearance of an abdominal mass;
• Abdominal pain;
• Unexplained weight loss;
• Fatigue;
• Anemia.

In some cases, the first symptom is pain in the stomach area. The increase in the tumor mass can partially block the passage of digested food, which intensifies the pain. Complete intestinal obstruction causes vomiting, bloating, and severe abdominal pain.

Diagnosis of small intestine cancer

Early detection of cancer often allows for more treatment options. Since it is a rare cancer, screening tests are not performed to detect neoplasia in asymptomatic individuals.

Regular exams are recommended for people with certain hereditary genetic syndromes that have an increased risk of small intestine tumors, especially in 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 tumors to become more visible. It is not the best test, however, it is cheaper, making it more accessible;

• Upper gastrointestinal series – the exam evaluates the esophagus, stomach, and the first part of the small intestine (duodenum). The barium contrast, when ingested, coats the lining of the esophagus, stomach, and small intestine. Since X-rays do not pass through barium, it is possible to outline larger abnormalities in the lining of these organs;

• Enteroclysis – barium is delivered to the small intestine through a tube inserted through the mouth, passing through the stomach until it reaches the beginning of the small intestine, along with a substance that dilates the intestine. It allows for clearer images of the inside of the small intestine;

• Capsule endoscopy – allows for examination of the lining of the middle part of the GI tract, which includes all three portions of the small intestine, a part of the intestine that cannot be reached by upper endoscopy or colonoscopy.

The patient swallows a capsule containing a microscopic camera, a light source, and a tiny transmitter, which takes high-resolution images of segments of the digestive tract. The 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 is naturally eliminated through defecation. This exam does not require sedation, and the patient can return to their normal daily activities while the capsule travels through the GI tract;

• Computed tomography (CT) – an imaging diagnostic technique that uses X-rays in higher doses to visualize regions of the body. Using computerized techniques, the patient’s image is divided into small slices for better evaluation.

The equipment has an examination table that slides into the open equipment, which does not generate a feeling of claustrophobia. It can be with or without contrast and can be used to precisely guide the positioning of a biopsy needle into a suspected cancer area.

Often used to observe the chest and abdomen, to check if the disease has spread to the lymph nodes or other organs, such as the liver.

• Nuclear medicine scans – PET-CT is a nuclear medicine technique that combines a CT scan with the infusion of a radiotracer, a substance marked with a low radiation component. This allows for a functional evaluation in addition to the image, showing where the radiotracer is most concentrated. There are different types of markers.

In PET with FDG, glucose is labeled to indicate sites with higher metabolism, as neoplasms have intense glucose consumption. This exam is mainly requested in the case of lymphomas. In the case of carcinoid tumors, in addition to PET with FDG, PET with gallium and Octreoscan may also be requested, which are done with radiotracers that bind to somatostatin receptors and help define the treatment of the disease.

• Upper gastrointestinal endoscopy – allows the doctor to examine the inner lining of the esophagus, stomach, and the first part of the small intestine (duodenum). During the exam, tissue samples can be taken from suspicious areas, which will be later sent to a laboratory for analysis. Polyp removal during the exam is also important to prevent later transformation into a malignant disease.
• Colonoscopy – uses a special endoscope inserted through the anus into the colon. The doctor can view the lining of the rectum and the entire colon, as well as the very end of the small intestine. It is also possible to remove polyps and take samples for pathology examination.
• Double-balloon enteroscopy – is an endoscopic examination of the deeper parts of the small intestine. This examination uses sophisticated technology: in addition to using a video-endoscopic system designed specifically to examine the small intestine, a balloon is attached to one end of the device and inserted into the endoscope, while another balloon is attached to the other end, and both are used together.

The balloons are inflated and deflated safely and effectively using an air pump that allows precise control of the pressure inside them through touch. The examination can be performed orally or anally.

• Laboratory tests – a complete blood count investigates the red blood cell count, indicating if the patient has anemia. In the blood biochemical test, changes in liver enzymes can be evaluated, which may indicate the presence of metastases in this organ.
• Biopsy – the only way to confirm the presence of cancer is by performing a biopsy. In this procedure, a sample of tissue from the suspicious area is removed and sent for analysis by a pathologist. One way 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, surgical biopsy is necessary.
• Laboratory tests on biopsy samples – in the immunohistochemistry test, a portion of the sample is treated with synthetic antibodies that bind only to a specific protein in the cells. The antibodies cause color changes if the protein is present, and these changes can be seen under the microscope. This test is important for determining the histological type of the patient’s cancer. If there is suspicion of GIST, for example, KIT (also known as CD117) and DOG1 are tested. Most GIST cells have these proteins, but cells from most other types of cancer do not – therefore, this type of test is important for defining the type of tumor. Other proteins can also be tested, assisting the pathologist in defining the type of disease.

Treatment for intestinal cancer

The treatment for small intestine cancer depends on the type of cancer, whether the tumor can be completely removed with surgery, and whether the disease is localized or has spread to other organs.

Treatment for adenocarcinoma in the small intestine

• Surgery – when the cancer is only in or near the place where it began, without spreading, surgery is usually done to try to remove the entire tumor. If the cancer has spread too much to be completely removed, surgery may be done to help prevent or relieve problems caused by the tumor, which often grows large enough to block the intestine. The type of operation will depend on several 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 the intestine that contains the tumor, as well as some normal tissue around the tumor. Some nearby tissue containing lymph nodes is also removed. It can be done through an abdominal incision – open surgery – or, for some smaller tumors, laparoscopically, in which the operation is performed through several small incisions 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 more commonly 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 then connected to the small intestine so that bile from the liver can enter the small intestine.

• Palliative surgery – if the cancer cannot be completely removed, surgery can still be a good option to prevent or relieve some symptoms. This is called palliative surgery, which can be done to relieve a blocked intestine, reduce pain, nausea, and vomiting, and allow the patient to eat normally, for example.

• Chemotherapy – chemotherapy drugs attack cells during cell division, primarily affecting those that are rapidly replicating, such as cancer cells. They enter the bloodstream and can reach cancer cells anywhere in the body. They can be used when cancer has spread to other parts of the body or after the tumor is removed with surgery to decrease the chance of cancer coming back. In the case of lymphomas, this is the main treatment. 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, mouth sores, and diarrhea.

• Radiation therapy – uses high-energy radiation to kill cancer cells. It can be an option when cancer cannot be completely removed 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, radiation beams 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 at the site where the radiation beams passed, such as mild redness, blistering, and peeling.

Treatment for carcinoid tumors in the small intestine

Many gastrointestinal (GI) carcinoid tumors can also be cured with 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.

Several types of operations can be used to treat GI carcinoid tumors, and in some cases, they are similar to those used for adenocarcinoma. There are also specific procedures:

• Surgery for 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 tolerate surgery), other techniques may be used.

• Hepatic resection – in this operation, one or more parts of the liver containing cancerous areas are removed. If it is not possible to remove all areas of cancer, surgery can be done to remove as much tumor as possible to help reduce symptoms of carcinoid syndrome. This 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 performed using interventional radiology techniques.

• Chemotherapy – it is usually used only for tumors that have spread to other organs, that are causing severe symptoms, have not responded to other medications, or are high-grade. Other medications that can be used are small molecules, capable of interfering with intracellular metabolism.

• Nuclear medicine treatments – are treatments done with radioactive compounds coupled to specific molecules and that are injected into the patient.

• Radiation therapy – may be an option for those who cannot undergo surgery for some reason. It can also be administered after surgery in some cases, if there is a chance that part of the tumor may not have been removed. Radiation therapy can also be used to help relieve symptoms such as pain if the cancer spreads to the bones or other areas.

Treatment for small intestine 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 lymph nodes, which do not need to be removed.

If the tumor is large or has grown into other organs, the surgeon may still be able to remove it completely, often requiring the removal of parts of organs (such as a section of the intestines). Another option for large tumors or those that have grown into nearby areas may be to first take targeted medication. This is called neoadjuvant treatment, and it can often shrink the tumor, making it easier to remove with surgery.

• Targeted Therapy – some medications can target certain proteins in gastrointestinal stromal tumor (GIST) cells that help them divide and grow. These targeted drugs – also called targeted or precision therapy – are often very useful in treating GISTs. They work differently from conventional chemotherapy drugs, which are usually not helpful in these cases.

• Radiation Therapy – Radiation therapy is the use of high-energy X-rays (or particles) to kill cancer cells. Radiation is not very useful in treating GIST, so it is not used frequently. But sometimes it can relieve symptoms such as bone pain.

Treatment for Small Intestine Cancer (Lymphoma Type)

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 therapy. Surgery is often used to obtain a biopsy sample to diagnose and classify a lymphoma, but it is rarely used as a form of treatment.

• Immunotherapy – Immunotherapy is the treatment that stimulates the patient’s own immune system to kill lymphoma cells or slow their growth. Immunotherapeutic drugs prevent cancer from being camouflaged and undetected 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 target a specific target, such as a substance on the surface of lymphocytes (the cells where lymphomas begin). Several monoclonal antibodies are now used to treat non-Hodgkin lymphoma (NHL).
• High-dose chemotherapy and stem cell transplant – A stem cell transplant (also known as a bone marrow transplant) allows doctors to administer higher doses of chemotherapy, sometimes along with radiation therapy.

The doses of chemotherapy are typically limited by the side effects these drugs can cause. Higher doses cannot be used, even if 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 transplant of blood-forming stem cells to restore the bone marrow afterward.

Stem cell transplants are sometimes used to treat patients with lymphoma who are in remission or who have had a relapse during or after treatment.

There are two main types of stem cell transplants (SCTs):

• Autologous stem cell transplant – the patient’s own stem cells are used, collected several times in the weeks before treatment. The cells are frozen and stored while the person receives treatment (high-dose chemotherapy and/or radiation) and then returned to the patient’s bloodstream through an IV (intravenous catheter).

• Allogeneic stem cell transplant – the stem cells come from another person (a donor). It is usually a brother or sister, although the source can be an unrelated donor or umbilical cord blood.

Prevention for small intestine cancer

The exact reasons why people develop small intestine cancer are not known, but several factors can increase the risk of the disease, as mentioned earlier in the text. Avoiding them, when they are controllable (such as diet and smoking, for example), is a way to prevent the disease.

When unavoidable, such as with hereditary conditions and syndromes, keeping them monitored through regular exams can be a way to detect cancer in its early stages and increase the chance of a cure.