Serum immunoglobulin G fraction 4 levels in pancreatic cancer: elevations not associated with autoimmune pancreatitis.

CONTEXT: Autoimmune pancreatitis is an uncommon, inflammatory disease of the pancreas that presents with clinical features, such as painless jaundice and a pancreatic mass, similar to those caused by pancreatic cancer. Patients with autoimmune pancreatitis frequently have elevated serum immunoglobulin G fraction 4 (IgG4) levels, and their pancreatic tissue may show IgG4-positive plasma cell infiltration. It is imperative to differentiate autoimmune pancreatitis from pancreatic cancer because autoimmune pancreatitis typically responds to corticosteroid treatment. A previous Japanese study reported that serum IgG4 greater than 135 mg/dL was 97% specific and 95% sensitive in predicting autoimmune pancreatitis. OBJECTIVE: To prospectively measure serum IgG4 levels in pancreatic cancer patients to ascertain whether increased levels might be present in this North American population. DESIGN: We collected blood samples and phenotypic information on 71 consecutive pancreatic cancer patients and 103 healthy controls who visited our clinics between October 2004 and April 2006. IgG4 levels were determined using a single radial immunodiffusion assay. A serum IgG4 level greater than 135 mg/dL was considered elevated. RESULTS: Five cancer patients had IgG4 elevation, with a mean serum IgG4 level of 160.8 mg/dL. None of our cancer patients with plasma IgG4 elevation demonstrated evidence of autoimmune pancreatitis. One control subject demonstrated elevated serum IgG4 unrelated to identified etiology. CONCLUSIONS: As many as 7% of patients with pancreatic cancer have serum IgG4 levels above 135 mg/dL. In patients with pancreatic mass lesions and suspicion of cancer, an IgG4 level measuring between 135 and 200 mg/dL should be interpreted cautiously and not accepted as diagnostic of autoimmune pancreatitis without further evaluation.