iiiseases of the Pancreas
There are two main types of pancreatic cancer. Those that arise from the ductal cells of the exocrine pancreas are termed pancreatic ductal adenocarcinoma. This is the most common and most lethal type. Those that arise from the endocrine cells in the pancreas are termed pancreatic neuroendocrine tumors or islet cell tumors. This form has a wide spectrum of biologic activity ranging from benign and indolent to more aggressive endocrine carcinomas.
Pancreatic Cancer (Ductal Adenocarcinoma)
Pancreatic cancer is a lethal malignancy in which the anticipated mortality approaches the incidence of the disease. Patients with pancreatic cancer suffer the lowest survival rate with less than 5% surviving past 5 years. Pancreatic cancer is the fourth leading cause of cancer related death in the United States among men and women, with 45,200 new cases and 38,460 deaths expected this year. The average life expectancy is less than 6 months after a diagnosis of metastatic pancreatic cancer. Currently 52% of pancreatic cancer patients are initially diagnosed at this stage of disease. Pancreatic cancer currently receives 1% of available NCI research spending versus 20% spent on breast, colon and prostate combined. Each of these other malignancies has 15-20 times higher 5 year survival rates than pancreatic cancer.
Although pancreatic cancer only represents 3% of new cancer cases each year among men and women, the disease is responsible for 6% (men) or 7% (women) of all cancer related deaths in the United States.
Despite steady improvements is cancer related outcomes for many malignancies over the past several decades, the survival for patients with pancreatic cancer remains limited.
Pancreatic cancer has the ability to invade beyond the pancreas to surrounding structures (locally advanced) and to spread from the pancreas to distance sites (metastasis). The outcomes for patients are related to the extent of disease at presentation and the effectiveness of therapy which may include surgery, chemotherapy and radiation therapy.
Neuroendocrine (islet cell) tumors of the pancreas
Neuroendocrine tumors of the pancreas are rare, comprising less than 5% of all pancreatic tumors. Although some of these tumors over produce hormones that can be measured in the blood producing a clinical syndrome (such as insulinomas, glucagonomas, or gastrinomas), most of these tumors are nonfunctional.
Nonfunctional Neuroendocrine Tumors
Nonfunctional neuroendocrine tumors do not produce excess hormones. They have a wide spectrum of biologic activity, but many are slow growing and asymptomatic. If not found incidentally on an imaging study ordered for some other purpose, these tumors can be very large at presentation. While many of these tumors behave in a benign fashion, they do have the ability to metastasize.
Although often asymptomatic, these tumors can cause abdominal discomfort and jaundice. Neuroendocrine tumors often require a fairly extensive work up to secure the diagnosis. The blood level of chromagranin A will often be elevated. This tumor marker is good for observing response to therapy and for surveillance for possible recurrence in patients who have a known diagnosis of pancreatic neuroendocrine tumor, but it is not a good screening test and it is artificially elevated in patients who are taking anti-acid medication.
An MRI or CT scan of the abdomen will identify tumors that are at least 5 mm in dimension. An octreotide scan is a nuclear medicine exam that is specific for somatostatin receptor expressing tumors (like pnet’s) and will be positive in a majority of cases. It can be a useful test to rule screen for tumor recurrence. These tumors are typically visible on endoscopic ultrasound and can be biopsied to confirm the diagnosis.
Treatment is individualized based on the size, location, distribution of disease and the overall health of each patient. In general, however, patients with tumors localized to the pancreas will be offered surgical removal. Many small tumors can be enucleated (scooped out) of the pancreas, while others will require formal removal of a portion of the pancreas (whipple, distal pancreatectomy, central pancreatectomy). Those with disease that has spread to the liver, will have the options of surgery, ablation therapy and chemoembolization, depending on the extent of disease.
Insulinomas are islet cell tumors of the pancreas that over produce insulin. This causes a decrease in the blood sugar of these patients giving rise to symptoms of dizziness, fatigue, weakness, uncontrolled shaking, hunger, and at times psychiatric disturbances. Most of these tumors are small and benign (90%).
The diagnosis of insulinoma is based on Whipple’s triad which is a combination of three clinical features that indicate the presence of an insulinoma: (1) attacks of fainting, dizziness, and sweating on fasting; (2) severe hypoglycaemia present during the attacks; (3) relief from the attacks achieved by administering glucose. The formal diagnosis of an insulinoma often requires admission to the hospital for an observed 72 hour fast. Blood is drawn to measure the glucose and insulin levels when the patient develops symptoms of low blood sugar.
Once the diagnosis is made, the tumor needs to be localized in anticipation of surgical removal. These tumors can be visualized on CT, MRI, octreotide scan and endoscopid ultrasound. Once the tumor is identified, it is removed surgically. This can often be accomplished by an enucleation, but sometimes it will require removal of a portion of the pancreas.