Two New Studies Profile Prognostic Factors for Breast Cancer
Two new studies provide insight into the use of new and standard prognostic factors for women with breast cancer. The first, conducted by Dr. Massimo Cristofanilli and colleagues at several prominent U.S. cancer research centers, confirms the long-held hypothesis that the number of cancer cells in the blood are a direct indicator of disease severity. The results are published in the August 19 New England Journal of Medicine.
This research was performed using a new test - the CellSearch System - which uses antibody-coated magnetic beads followed by fluorescently labeled monoclonal antibodies to distinguish cancerous epithelial cells from leukocytes in a blood sample. The test was developed by the research sponsor, Immunicon Corp.
All 177 women in the study group had metastatic breast cancer and were starting a new course of systemic treatment. The women began the study with standard imaging of metastatic sites and a baseline test for the number of cancer cells in their blood, followed by another blood test approximately 4 weeks later and additional imaging around 10 weeks after baseline. A comparison of these data points, with consideration of various cancer risk factors, showed that circulating tumor cells were a useful predictor of disease progression and survival in these women. Analysis also showed that five cancer cells per 7.5 milliliters of blood was the cutoff for determining a poor prognosis or the likelihood of progression-free survival. Women above the cutoff had a significantly shorter survival period - a median of 10 months - compared with more than 18 months of progression-free survival for women below the cutoff.
The authors note that the CellSearch System is not proven as a reliable screening tool for metastatic breast cancer. They do, however, see its promise as a means of determining treatment efficacy much earlier than was previously possible - within 3 to 4 weeks of initiation - compared with the 8 to 12 weeks that imaging studies require.
"This test has the potential to change clinical management," Dr. Cristofanilli said in an interview with Reuters Health. "One day, we may be able to suggest to a patient, based on personal risk, a more aggressive treatment, a less aggressive treatment, or no treatment at all."
The second study, published in the September 1 Journal of the National Cancer Institute by Dr. Catherine Schairer and colleagues at the National Cancer Institute's (NCI's) Division of Cancer Epidemiology and Genetics, showed that the probability of death from breast cancer varied substantially when taking into consideration standard prognostic factors such as age at diagnosis, tumor size, estrogen receptor (ER) status, and stage of disease. Overall, probability of death from breast cancer relative to death from other causes generally declined with age within stage, but increased with advancing stage of disease, regardless of age, in both white and black patients. Young women who are diagnosed with breast cancer, and women of all ages who are diagnosed with breast cancer in its advanced stages, are more likely to die from it than from any other cause.
To develop better estimates of the risk of death from breast cancer and other causes in breast cancer patients, Dr. Schairer and her team analyzed Surveillance, Epidemiology, and End Results Program data from more than 400,000 breast cancer patients diagnosed between 1973 and 2000. They calculated probabilities over a 28-year follow-up period according to the women's age at diagnosis, stage of disease, and race. More recent data allowed additional analysis according to tumor size and ER status over an 11-year period.
"To our knowledge, this is the first comprehensive competing-risk analysis to quantify the probability of death from breast cancer and other causes after a diagnosis of breast cancer," said Dr. Schairer. "These results can provide important prognostic information to physicians and patients, and may help in weighing the risks and benefits of various treatment options, particularly in older women."
Dr. Schairer also believes that future studies, such as similar analyses for other cancers and more in-depth analyses for breast cancer according to tumor size and hormone receptor status, could generate additional valuable tools for physicians and patients.