CHICAGO--The Truquant BR RIA blood test (manufactured by Biomira Diagnostics, Inc.) has been shown to be a highly specific predictor of recurrent breast cancer. In clinical trials, positive test results predicted relapse 83% of the time, providing as much as a 12-month (average, 5 month) warning over clinical symptoms and/or other diagnostic methods for breast cancer recurrence.
The test, which costs about $50, works by detecting the CA27.29 antigen, a tumor marker present in breast cancer cells, said Herbert Fritsche, PhD, a biochemist and associate professor of laboratory medicine at M.D. Anderson Cancer Center. He spoke at the the American Association for Clinical Chemistry meeting.
While the normal gene product is heavily glycosylated and does not allow for antibody recognition, the tumor mucin gene product lacks glycosylation and opens at sites that then act as the basis for monoclonal antibody detection. As breast cancer metastasizes, glycoprotein is shed into the bloodstream in high levels, alerting clinicians to a recurrence.
The Truquant BR test was evaluated in a 3-year multicenter, double-blind prospective study of 166 previously treated patients with stage II or III breast cancer; all were clinically free of disease at the time of enrollment. Over the course of 2 years, cancer recurred in 26 women. Sensitivity of the blood test in predicting recurrence was 58%, specificity was 98%, positive predictive value was 83%, and negative predictive value was 93%.
Approved Last April
"This was very striking data," Dr. Fritsche said. "In fact, it convinced the FDA to approve the test last April despite the small number of patients." The test was approved for use in previously treated patients with stage II or III breast cancer in conjunction with other clinical detection methods.
Further research is now being conducted to confirm these preliminary data, he said. In addition, it has yet to be shown that use of the antibody test has an impact on breast cancer outcome.