New RIA Blood Test Predicts Breast Cancer Recurrence

CHICAGO--The Truquant BR RIA blood test (manufactured by BiomiraDiagnostics, Inc.) has been shown to be a highly specific predictorof recurrent breast cancer. In clinical trials, positive testresults predicted relapse 83% of the time, providing as much asa 12-month (average, 5 month) warning over clinical symptoms and/orother diagnostic methods for breast cancer recurrence.

The test, which costs about $50, works by detecting the CA27.29antigen, a tumor marker present in breast cancer cells, said HerbertFritsche, PhD, a biochemist and associate professor of laboratorymedicine at M.D. Anderson Cancer Center. He spoke at the the AmericanAssociation for Clinical Chemistry meeting.

While the normal gene product is heavily glycosylated and doesnot allow for antibody recognition, the tumor mucin gene productlacks glycosylation and opens at sites that then act as the basisfor monoclonal antibody detection. As breast cancer metastasizes,glycoprotein is shed into the bloodstream in high levels, alertingclinicians to a recurrence.

The Truquant BR test was evaluated in a 3-year multicenter, double-blindprospective study of 166 previously treated patients with stageII or III breast cancer; all were clinically free of disease atthe time of enrollment. Over the course of 2 years, cancer recurredin 26 women. Sensitivity of the blood test in predicting recurrencewas 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. "Infact, it convinced the FDA to approve the test last April despitethe small number of patients." The test was approved foruse in previously treated patients with stage II or III breastcancer in conjunction with other clinical detection methods.

Further research is now being conducted to confirm these preliminarydata, he said. In addition, it has yet to be shown that use ofthe antibody test has an impact on breast cancer outcome.

Dr. Fritsche noted that bone scans and other commonly used diagnostictests do little to improve survival and should not be used inasymptomatic patients. Symptoms are still the best indicator ofdisease recurrence in breast cancer. The researchers, therefore,decided to see how the Truquant BR test related to symptoms asan indicator of recurrence.

"The numbers are meager but interesting," he said. Only3 of 32 patients who had bone pain during monitoring had recurrentdisease to bone, and the test showed that these three had elevatedantigen levels. Twenty-nine patients had bone pain that was notrelated to recurrence, and all had normal antigen levels. Datalike these might be used to determine which patients should haveadditional expensive, invasive testing.

"The whole idea is to do something immediately once we knowthe disease has recurred," Dr. Fritsche said. "For patientswith local or regional disease, there is the hope that they canbe treated again locally with radiation or surgery, which wouldsignificantly extend their lives. For metastatic patients, thebest we can hope for is that early detection and aggressive treatmentcan lengthen their survival."

Dr. Fritsche said that planning is underway to monitor all stageII and III patients at M. D. Anderson with the antigen test. Thosewho test positive will be retested at 1-month intervals. If theirrise in antigen level is confirmed but no metastasis is found,patients will be given the choice of chemotherapy or continuedmonitoring. If metastasis is detected, they will go on to theappropriate protocol.