Each year, over 45,000 people in the United States are diagnosed with pancreatic cancer, representing approximately 3% of all newly diagnosed cancers.1 Pancreatic cancer is also the fourth leading cause of cancer death.1 The diagnosis and treatment of pancreatic cancer can be challenging to both patients and health care professionals. To confirm a diagnosis and assess treatment response, one of the most commonly used tumor markers to is serum CA 19-9. Although it is frequently used, it should only be ordered when clinically indicated.
When ordering a serum CA 19-9 level, it is important to keep in mind its sensitivity and specificity. According to an extensive review of the literature, the sensitivity of CA 19-9 was between 79% and 81%, and its specificity was 82% to 90% in patients who are symptomatic on presentation.2 Patients with newly diagnosed pancreatic cancer may present with weight loss, painless jaundice, and epigastric abdominal pain that radiates to the back, among other symptoms. CA 19-9 has a low positive predictive value (between 0.5% and 0.9%), therefore, it has limited utility as a screening test.2 Furthermore, a patient must have the Lewis blood group antigen—present in approximately 90% to 95% of the population—in order to express CA 19-9, therefore, it would not be useful in the remaining 5% to 10% of the population.2
Once formally diagnosed with pancreatic cancer, the absolute value of CA 19-9 prior to surgical intervention can provide information on the patient’s prognosis. Levels greater than 100 IU/mL are typically not resectable and may be indicative of metastatic disease; on the other hand, levels lower than 100 IU/mL are usually consistent with resectability.2 Patients with pancreatic cancer who have normal levels (< 37 IU/mL) have a longer median survival (32-36 months) when compared with patients with CA-19-9 levels above 37 IU/mL (12-15 months).2
After chemotherapy and/or surgery, it is important to trend the CA 19-9 levels in order to monitor response to therapy. Prolonged survival is associated with CA 19-9 levels that decrease by 20% to 50% from their baseline level within 6 to 8 weeks of treatment.2
There are additional clinical scenarios that may complicate the interpretation of an elevated CA 19-9, including obstructive jaundice, cirrhosis, cholangitis, and other gastrointestinal (GI) cancers.2 GI cancers that can also have elevated CA 19-9 levels include cholangiocarcinoma, as well as gallbladder, hepatocellular, gastric, and colorectal cancer.
Based on the aforementioned issues with using CA 19-9 in certain clinical situations, there is accumulating data on additional laboratory tests that may aid in the diagnosis and treatment of pancreatic cancer. Samples from a patient’s stool, salivary glands, and pancreatic enzymes have provided some data that may prove useful in the future.3 Although some of the preliminary data is promising, the collection of such samples may provide a challenge and barrier to their routine use, as opposed to a simpler blood test, such as CA 19-9.
Biomarkers represent an increasingly popular area of research, particularly in the area of oncology. In addition to monitoring CA 19-9 levels, other biomarkers such as macrophage inhibitory cytokine-1 (MIC-1), carcinoembryonic antigen cellular adhesion molecule-1 (CEACAM-1), mucins, matrix metalloproteinase (MMP), tissue polypeptide-specific antigen (TPS), and regenerating gene family member 4 (REG-4) may one day prove to be clinically relevant and useful.3 Before these tests become routine orders, more research is needed in order to further define how these biomarkers can help guide the management of the patient’s cancer.
When performing a work-up for pancreatic cancer, clinical judgment should be used when deciding on blood tests and imaging. CA 19-9 is an important tumor marker that can help guide the diagnosis and treatment of pancreatic cancer; however, it is always important to consider how a specific test will be used to change medical management for a patient prior to ordering it.
- Siegel R, Naishadham D, Jemal A. Cancer Statistics, 2013. CA Cancer J Clin. 2013;63(1):11-30.
- Ballehaninna UK, Chamberlain RS. Biomarkers for pancreatic cancer: promising new markers and options beyond CA 19-9. Tumour Biol. 2013;34(6):3279-3292.92.
- Ballehaninna UK, Chamberlain RS. The clinical utility of serum CA 19-9 in the diagnosis, prognosis and management of pancreatic adenocarcinoma: An evidence based appraisal. J Gastrointest Oncol. 2012;3(2):105-119.