Gastric Carcinoid Tumors - Causes, Symptoms, and Treatment

Introduction

Carcinoid tumors fall under a category of tumors known as neuroendocrine tumors. These tumors develop in the neuroendocrine cells that are in charge of producing hormones in response to various nerve signals. Although these cells are present in various body parts, they are commonly found in the digestive tract. The neuroendocrine cells present in the gastrointestinal tract produce hormones that help in controlling digestive juices and muscles responsible for passing food through the stomach and intestines. Studies suggest that around 60 percent of carcinoid tumors develop in the gastrointestinal tract. The gastrointestinal (GI) tract is an integral part of the digestive system. The GI tract helps in digesting food, taking the nutrients from the food to be distributed to various body parts, and disposing of waste materials from the body.

What Is a Gastric Carcinoid Tumor?

A gastric carcinoid tumor is a cancer that occurs in the gastrointestinal tract. The common sites of occurrence are the small intestine, appendix, and rectum, which is a portion of the large intestine. Neuroendocrine cells present in the gastrointestinal tract typically make hormones that control the breakdown of food in the body. But in gastric carcinoid tumors, these cells produce excess amounts of hormones that are not required for the body. This can cause problems like flushing, heart issues, and diarrhea. However, gastric carcinoid tumors grow very slowly and are not common as other tumors of the GI tract.

What Are the Causes of Gastric Carcinoid Tumors?

The exact cause of gastric carcinoid tumors is unknown. It is believed that gastric carcinoid tumors are caused due to changes in some genes. These genetic changes either deactivate the tumor suppressor genes (genes that control abnormal cell division and protect from cancer) or activate the oncogenes (a group of genes that may promote cell division and cause normal cells to become cancerous). According to studies, some of the factors that increase the risk of gastric carcinoid tumors are as follows:

• Gender: It is more common in women than men.

• Family history of cancer, particularly in a first-degree relative.

• Conditions of the stomach like Zollinger-Ellison syndrome, pernicious anemia, or atrophic gastritis.

• Genetic disorders like neurofibromatosis type 1 or multiple endocrine neoplasia type 1.

• Tobacco smoke.

What Are the Symptoms of Gastric Carcinoid Tumors?

The symptoms of gastric carcinoid tumors may vary from person to person. They are as follows:

• Diarrhea.

• Abdominal pain.

• Difficulty in passing stools.

• Nausea and vomiting.

• Rectal bleeding and pain.

• Skin flushing.

• Bloating.

• Unexplained weight loss.

• Blood in stools.

• Heartburn.

• Change in the color of the stools.

• Jaundice.

• Extreme tiredness.

How to Diagnose Gastric Carcinoid Tumors?

The methods of diagnosing gastric carcinoid tumors are as follows:

• Medical History: The doctor takes a detailed history regarding the lifestyle, health conditions, previous illness, symptoms experienced, and treatments undergone by the patient.

• Physical Examination: The doctor carefully examines the body and looks out for any unusual signs like a lump in the abdomen region or enlarged liver.

• Blood and Urine Tests: These are done to check the hormone or protein levels that could indicate a tumor. Mostly the blood samples of patients with gastric carcinoid tumors contain a hormone produced by the tumor. The urine sample may contain serotonin hormone.

• Tumor Marker Test: A urine, blood, or tissue sample of the patient is checked for tumor marker substances like chromogranin A.

• CT (Computed Tomography) Scan and MRI (Magnetic Resonance Imaging): A CT scan of the abdomen or chest is taken to find out if the tumor has spread to the neighboring lymph nodes or organs like the liver. MRI uses radio waves, a magnet, and a computer to take a detailed image of various organs of the body. MRI often provides a clearer picture than a CT scan.

• PET (Positron Emission Tomography) Scan: This is used to detect the tumor cells in the body by injecting radioactive glucose into the vein. The tumor cells appear brighter in the image as they absorb more glucose than the normal cells.

• MIBG (Meta-Iodobenzylguanidine) Scan: This scan is used to locate carcinoid tumors. A radioactive material, MIBG, is injected into the body through a vein. As the radioactive material travels through the bloodstream, it is absorbed by the tumor cells. The absorbed radioactive material is detected by a device that measures radiation. A high level of material absorption may indicate the presence of the tumor.

• Octreoscan: This procedure is similar to the MIBG scan except that the radioactive substance used is octreotide.

• Upper Endoscopy: This procedure is used to observe organs of the body, like the stomach, small intestine, etc., for abnormalities using a thin instrument called an endoscope that has a camera attached to it.

• Colonoscopy: Colonoscopy is a procedure to view the rectum and colon for any abnormalities, polyps, or cancer using a thin instrument called a colonoscopy.

• Capsule Endoscopy: Capsule endoscopy is a procedure used to view the small intestine. During this procedure, the patient is asked to swallow a capsule containing a small camera that takes pictures while the capsule moves along the gastrointestinal tract. The pictures are sent to a receiver which is placed outside the patient’s body.

• Biopsy: A biopsy involves taking a sample of cells or tissues and viewing them under the microscope to detect cancer signs.

What Are the Treatment Options for Gastric Carcinoid Tumors?

The treatment options vary according to the location and size of the tumor. The various treatment options are as follows:

1. Surgery: It is the most common mode of treatment for carcinoid tumors. The different surgical techniques used are as follows:

   1. Local Excision: It is the removal of the tumor and a small area of tissue around it.

   2. Resection: It is a procedure that removes a part or the entire organ that contains cancer, along with the nearby lymph nodes.

   3. Endoscopic Resection: It is a surgical procedure that removes small tumors of the gastrointestinal tract lining with the help of an endoscope.

   4. Cryosurgery: Also known as cryotherapy, it is a procedure that is used to freeze and destroy the tumor using an instrument.

   5. Radiofrequency Ablation: This technique uses a probe with electrodes that emit high-energy radio waves, which can kill the tumor cells.

   6. Hepatic Artery Embolization: This technique is used if the tumor has spread to the liver. This involves blocking the hepatic artery, which is the main blood vessel supplying the liver. Blocking the blood flow to the liver helps in destroying the cancer cells growing in the liver.

2. Radiation Therapy: Radiation therapy uses high-energy X-rays or other sources of radiation to kill cancer cells. The two types of radiation therapy are as follows:

   1. External Radiation Therapy: In this method, radiation is sent from a machine located outside the body to the area where the tumor is present.

   2. Internal Radiation Therapy: This method involves using radioactive substances sealed in things like wires, catheters, needles, or seeds that are placed in the tumor area.

Radiopharmaceutical therapy involves taking a pill that has radioactive substances like MIBG or Iodine I-131. The tumor absorbs the substance, and the radiation kills the tumor cells.

• Hormone Therapy: This method involves treating gastric carcinoid tumors using man-made hormones octreotide and lanreotide that are injected into the body. These are to be taken every month. This method reduces the hormones produced by the tumor and slows down the tumor growth.

• Chemotherapy: It is a form of treatment that uses drugs to destroy the tumor cells. This therapy is commonly used when the tumor starts to grow while the patient is on hormone therapy.

• Targeted Therapy: This is an advanced mode of treatment that uses drugs and other materials to target and attack specific tumor cells.

Conclusion

Carcinoid tumors are most commonly seen to develop in the gastrointestinal tract. Since it is a slow-growing tumor that does not show many symptoms in patients, it often goes undiagnosed. But when left untreated, these tumors can cause serious complications. Hence any suspicious symptoms should be discussed with a doctor at the earliest. Following a good treatment plan can help the patient get rid of the tumor and lead a normal life.