CA-50 and CA-19.9 as tumour markers: which is preferable?

CA-50 (Kit IRMA Stena Diagnostic, cut-off value: 16 U/ml) and CA-19.9 (Kit SPAC Mallinckrodt were compared in a prospective study including 323 cancer patients (56% metastatic) and 120 patients with non neoplastic disease. The CA-50 and CA-19.9 sensitivities were 41.8% and 39% respectively; the CA-50 sensitivity was greater in the cancers of the gastro-intestinal (GI) tract (61.3% versus 51.6% alpha less than 0.00001) and did not differ in the other cases. The CA-19.9 specificity was greater (77.5% versus 64.2% alpha less than 0.0001), due to a greater specificity in the case of respiratory diseases (86.7% versus 66.7% alpha less than 0.0001). A good correlation was found between the serum levels of the two markers in each group of patients (cancer r = 0.78, alpha less than 0.001; benign diseases r = 0.69, alpha less than 0.001). This study has shown a close correlation between these two markers; the reliabilities of CA-50 and CA-19.9 were similar, particularly in the gastro-intestinal diseases (58.3% versus 51.3%). In conclusion, CA-50 and CA-19.9 are both good markers of cancers of the GI tract. Their simultaneous assay would be useless.