At a symposium sponsored by Schering-Oncology/Biotech, 16 researchers involved in studies of the investigational antiestrogen agent toremifene(Drug information on toremifene) (Fareston) discussed its potential role in the treatment of patients with advanced breast cancer and as adjuvant therapy, as well as other breast cancer issues. Previous articles in this series appeared in January 1997 , February 1997 , and March 1997
PALM SPRINGS, Calif--Although most of the mucin markers used to detect breast cancer recurrence were developed by different laboratories at different times, all recognize the products of the MUC 1 gene, Roy Beveridge, MD, of Fairfax Oncology/Hematology Associates, Annandale, Va, said at the symposium.
CA 15-3 is not specific for breast cancer, he said. Half of patients with prostate, ovarian, or pancreatic cancer, for example, have an elevated CA 15-3. Roughly half of patients with stage IV breast cancer have an elevated CA 15-3, and between 10% and 20% of stage II patients have elevations of this marker.
Although newer versions of CA 15-3 are being developed, its value is currently limited because of assay variability and the wide range of levels considered normal. "Unless the level doubles, it doesn't mean very much," he said.
CA 27-29 (Truquant BR RIA) is similar to CA 15-3 but may be more specific. The intra-assay variability is perceived to be less with CA 27-29 than with CA 15-3 tests, he said, and many labs have switched to the FDA-approved CA 27-29 marker.
CA 27-29 was evaluated in a prospective double-blind multicenter clinical trial of about 200 patients with stage II or III breast cancer who were clinically free of disease at the time of enrollment.
Of the 26 patients who had recurred at four years, 15 had an elevated CA 27-29, yielding a specificity of 98% and sensitivity of about 60%. The lead time (from tumor diagnosis to elevated CA 27-29) in patients who had distant metastasis was six to seven months. In patients who had local regional disease, it was two months, presumably because the volume of disease is significantly less in these patients.
Of 29 patients with bone pain who had negative repeat bone scans, every one also had a negative CA 27-29. Of the three bone pain patients who had an elevated CA 27-29, all three had documented cancer recurrence. "So this mucin marker may have a particular value in bony disease," Dr. Beveridge said, since patients with elevated marker levels are good candidates for further testing.
The test probably has less value in patients with local regional disease, he said. However, in these patients, two consecutive elevations suggest continued disease growth, and, in that situation, "re-starting treatment or changing to a different regimen might be reasonable."
Within the medical community, Dr. Beveridge said, "many people say, well, you've identified metastatic breast cancer seven months before you would have found it by physical exam, but so what? You have no data to show that early treatment of metastatic disease improves survival." He answers that the information may be particularly useful in certain subpopulations such as patients with bone pain and younger patients who might want aggressive therapy when they are first diagnosed with metastatic disease.
When a member of the audience asked if an elevated CA 27-29 is an indication to treat the patient empirically, Dr. Beveridge said that in general it is not, "but there is a trial that is being organized right now to answer that question." When patients in the study group have an elevated CA 27-29, they will be given the choice of receiving empirical treatment or continued monitoring.