What tests do doctors use to diagnose pancreatic cancer?
Most people do not need to be screened for pancreatic cancer, and the tests available for screening frequently are complex, risky, expensive, or insensitive in the early phases of the cancer. Those who may qualify usually have a set of factors that increase the risk for pancreatic cancer, such as pancreatic cysts, first-degree relatives with pancreatic cancer, or a history of genetic syndromes associated with pancreatic cancer. Most screening tests consist of CT scans, ultrasounds, magnetic resonance cholangiopancreatography (MRCP), endoscopic retrograde cholangiopancreatography (ERCP), or endoscopic ultrasounds.
Most people with pancreatic cancer first go to their primary-care doctor complaining of nonspecific symptoms (see symptoms section above). Some warning signs include pain, gastrointestinal symptoms, weight loss, fatigue, and increased abdominal fluid. These complaints trigger an evaluation often including a physical examination (usually normal), blood tests, X-rays, and an ultrasound. If pancreatic cancer is present, the likelihood of an ultrasound revealing an abnormality in the pancreas is about 75%. If a problem is identified or suspected, frequently a computed tomography (CT) scan is performed as the next step in the evaluation; some clinicians prefer an MRI. If a pancreatic mass is seen, that raises the suspicion of pancreatic cancer and a doctor then performs a biopsy to yield a diagnosis.
Different strategies can be used to perform a biopsy of the suspected cancer. Often, a needle biopsy of the liver through the belly wall (percutaneous liver biopsy) will be used if it appears that there has been spread of the cancer to the liver. If the tumor remains localized to the pancreas, biopsy of the pancreas directly usually is performed with the aid of a CT. A direct biopsy also can be made via an endoscope put down the throat and into the intestines. A camera on the tip of the endoscope allows the endoscopist to advance the endoscope within the intestine. An ultrasound device at the tip of the endoscope locates the area of the pancreas to be biopsied, and a biopsy needle is passed through a working channel in the endoscope to obtain tissue from the suspected cancer. Ultimately, a tissue diagnosis is the only way to make the diagnosis with certainty, and the team of doctors works to obtain a tissue diagnosis in the easiest way possible.
In addition to radiologic tests, suspicion of a pancreatic cancer can arise from the elevation of a "tumor marker," a blood test which can be abnormally high in people with pancreatic cancer. The tumor marker most commonly associated with pancreatic cancer is called the CA19-9. It often is released into the bloodstream by pancreatic cancer cells and may be elevated in patients newly found to have pancreatic cancer. Unfortunately, although the CA19-9 test is cancer-related, it is not specific for pancreatic cancer. Other cancers as well as some benign conditions can cause the CA 19-9 to be elevated. Sometimes (about 20% of the time) the CA19-9 will be at normal levels in the blood despite a confirmed diagnosis of pancreatic cancer, so the tumor marker is not perfect. It can be helpful, however, to follow during the course of illness since its rise and fall may correlate with the cancer's growth and help guide appropriate therapy.