Prevalence and clinical significance of enormously increased CA 19.9 concentrations in hospitalised patients

Background: Markedly elevated CA 19.9 concentrations in serum are regarded as specific enough to reliably identify pancreatic cancer, even if a consistent body of literature shows CA 19.9 concentrations >1000 kU/L in a variety of benign conditions. Scarce data are, however, available on the prevalence and clinical significance of CA 19.9 values >10,000 kU/L. Here we present a case series of consecutive patients admitted to our hospital with CA 19.9 concentrations >10,000 kU/L, with the aim to assess the association of such concentrations with the presence of pancreatic cancer and, more in general, with tumours of the gastrointestinal system. We also tried to define whether the exact measurement of CA 19.9 concentrations in this range, which needs serial sample dilutions, is cost-effective. Methods: CA 19.9 measurements, including a 1:10 sample dilution in accordance to manufacturer’s instructions allowing the determination of concentrations up to 10,000 kU/L, were performed on Roche Modular EVO system. Samples with higher CA 19.9 values were diluted according to a defined laboratory protocol to obtain estimates up to 100,000 kU/L. Results: During 14 months, 18 patients showing an enormous elevation of CA 19.9 concentrations (11,568 to >100,000 kU/L) were identified (55% males; median age 73.5 years, range: 58- 85). Accordingly, the yearly prevalence of hospitalized patients tested for CA 19.9 and with marker concentrations >10,000 kU/L was 2.9%. All recruited patients were diagnosed as malignancies: 15 had primary or secondary pancreatic cancer, two had gastric cancer and one a cholangiocarcinoma. CA 19.9 concentrations ranged between >10,000-30,000 kU/L in 9 cases, >30,000-60,000 kU/L in two, >60,000-100,000 kU/L in three and >100,000 kU/L in four cases, respectively. A surgical resection of the tumour was performed in 5 patients, independently of CA 19.9 concentrations. The median patient’s survival was <6 months. Conclusions: CA 19.9 concentrations >10,000 kU/L unequivocally identify a gastrointestinal malignancy, more frequently (~83%) a primary or secondary pancreatic cancer. Exactly measuring CA 19.9 concentrations >10,000 kU/L after multiple sample dilutions does not add relevant information for patients’ prognosis and treatment.