CANCER ANTIGEN (CA) 27.29

This test is used to monitor metastatic carcinoma of the breast. CA 27.29 is a highly polymorphic glycoprotein belonging to the mucin family and is the product of the muc-1 gene. It is a useful measurement in the monitoring of both the course of disease and the response to therapy because there is a direct correlation between the changing levels of CA 27.29 and clinical status. In woman with known metastases, a reduction in levels of this marker indicates a good response to treatment while increasing levels indicate resistance to therapy and progressive disease and justify further clinical evaluation and regular monitoring. It has also recently been shown that an elevation of CA 27.29 levels above the upper limit of normal in woman with no clinical evidence of disease is an early indicator of recurrence. Elevated serum CA 27.29 levels found in woman in remission of stage II or III breast cancer provided a positive predictive value of 83.3% for recurrent disease, with an average lead time of 5.3 months before recurrence was clinically established.