Glucagon is a hormone produced by the pancreas. Glucagon works in balance with insulin to control the amount of sugar in your blood. One form of pancreatic cancer is glucagonoma. Glucagonoma tumor cells produce large amounts of glucagon. The high levels of glucagon create severe symptoms that are painful and life threatening. About five to 10 percent of tumors that develop in the pancreas are glucagonomas.
There are no known direct causes of glucagonoma. There are some risk factors, including genetic ones. If you have a family history of a syndrome called Multiple Endocrine Neoplasia Type I (MEN I), you have a greater risk of developing glucagonoma. But people develop these tumors who have no other risk factors.
Tumors that produce excess glucagon are cancerous (malignant) about 60 percent of the time. Malignant glucagonomas spread into other tissues—usually the liver—and start interfering with the function of other organs.
Having a tumor that produces large quantities of glucagon affects many aspects of your health. Glucagon balances the effects of insulin on the amount of sugar in your blood. If you have too much glucagon, your cells do not store sugar. Instead, sugar stays in the bloodstream.
This leads to diabetes symptoms and other painful and dangerous symptoms, including:
- high blood sugar
- excessive thirst and hunger (due to high blood sugar)
- inflamed mouth and tongue, cracking at the corners of the mouth
- waking up to urinate frequently at night
- skin rash (dermatitis) on the face, belly, buttocks, and feet (often crusty or filled with pus)
- unintentional weight loss
- blood clots in the legs (deep vein thrombosis)
Often, the symptoms appear to be caused by another condition. It may be years before the correct diagnosis is made.
Diagnosis is initially made with several blood tests. High glucagon levels are the hallmark of this condition. Other anomalies include high blood sugar, high levels of chromogranin A (a protein often found in carcinoid tumors), and anemia (low levels of red blood cells).
These tests are followed up with a computed tomography (CT) scan of the abdomen to look for the presence of tumors.
Often, tumors are large (4 to 6 centimeters wide) when they are discovered. Unfortunately, the cancer is often not discovered until it has spread to the liver.
There are two parts to treatment for glucagonoma: removing the tumor cells and treating the effects of too much glucagon.
It is best to begin treatment by removing the effects of the excess glucagon. This is often done by taking a somatostatin analogue drug, such as an injection of octreotide (Sandostatin). Octreotide helps to counteract the skin effects of glucagon and improve the intense skin rash.
Intravenous or tube feeding to improve your nutrition may also be done if you have lost a great deal of weight. Your high blood sugar will be treated with insulin and close monitoring of your blood glucose levels.
You may also be given an anticoagulant medication, or blood thinner. This prevents the formation of blood clots in the legs (deep vein thrombosis). For patients at risk of deep vein thrombosis, a filter can be placed in one of the large veins (the inferior vena cava) to prevent clots from reaching the lungs.
Once you are healthy enough for surgery, the tumor is usually surgically removed. Unfortunately this type of tumor rarely responds well to chemotherapy. Surgery is most successful if the tumor is caught while it is still confined to the pancreas.
Exploratory surgery of the abdomen may be done with an open incision (a large cut to the belly to examine the organs in the abdomen) or laparoscopically (with smaller cuts to allow cameras, lights, and tools). As much of the tumor as possible is removed. This may include part of the pancreas, local lymph nodes, and even part of the liver.
Most glucagonomas occur in the left side or tail of the pancreas. Removal of this section is called a distal pancreatectomy. In some patients, the spleen is also removed. When the tumor tissue is examined under a microscope, it is difficult to tell whether it is cancerous. If it is, your surgeon will remove as much of the tumor and surrounding healthy area as possible to try to prevent the tumor from spreading further.
Once the tumor is removed, the effect of the excess glucagon decreases immediately. However, two-thirds of all glucagonomas are malignant. These tumors can spread throughout the body and invade other organs. Unfortunately, by the time glucagonoma is diagnosed, the cancer has usually spread to other organs, such as the liver. Only 20 percent of patients can be completely cured with surgery.
If the tumor is limited to only the pancreas, the five-year survival rate is 85 percent (that is, 85 percent of patients live for five years after surgery). If the tumor has spread to other organs, but more than 90 percent of the tumor is successfully removed, there is a 60 to 80 percent rate of five-year survival, and most patients no longer have significant symptoms of excess glucagon.
Excess glucagon leads to symptoms of diabetes. High blood sugar can cause nerve damage, blindness, metabolic problems, and brain damage. Deep vein thrombosis can cause blood clots to travel to the lungs and cause death.
If the tumor invades the liver, it can eventually cause liver failure.