According to an article recently published in the Journal of Clinical Oncology, mitotic activity index (MAI) in cancer cells of women younger than 55 years of age with lymph node-negative early breast cancer may be one of the greatest predictors of a cancer recurrence among standard tests. Women with a high risk of a recurrence according to MAI may wish to pursue more aggressive therapeutic approaches than their counterparts.
Breast cancer claims the lives of approximately 40,000 women annually in the United States alone. Early breast cancer, or cancer that has not spread from the breast, has a high cure rate following standard therapy. One of the greatest predictors of a cancer recurrence is the presence of cancer cells in the axillary (under the arm) lymph nodes. Those with no cancer spread to these lymph nodes (lymp-node-negative) have higher rates of overall survival compared to those with cancer spread to the lymph nodes (lymph-node-positive). Long-term prognosis is also worse among younger, premenopausal women than the elderly, as the cancer tends to be more aggressive in these women.
Optimal therapy for women with early breast cancer, particularly those with lymph-node-negative disease, must be weighed with risks of recurrence against side effects of therapy. Therefore, researchers continue to evaluate patient or disease characteristics or variables that help predict a patient’s prognosis. This information may spare patients with a good prognosis from unnecessary treatment, while those with a poorer prognosis may benefit from additional therapy.
Mitotic activity index is a type of test that measures the time it takes for a cell to replicate. Theoretically, cancer cells that replicate more quickly are more aggressive. According to MAI, a “score” is given to indicate the speed of replication. Previous results from studies have associated MAI with outcomes in breast cancer; however, these findings need further validation before they are accepted into clinical practice.
Researchers associated with the multicenter mammary carcinoma project (MMMCP) conducted a clinical study in the Netherlands to evaluate the effectiveness and feasibility of using MAI as an indicator of prognosis in women with early breast cancer. The study included nearly 3,500 women under the age of 55 years who were diagnosed with early breast cancer. Five hundred and sixteen patients had no cancer spread to lymph nodes (lymph-node-negative). None of the women underwent chemotherapy.
The spread of cancer (metastasis) to distant sites in the body occurred in nearly 25% of patients. In evaluating multiple variables (patient age; size of cancer; hormone-receptor status; and aggressiveness, or grade, of cancer as it looked under the microscope), MAI was the single most accurate predictor of the risk of a recurrence and survival in patients with lymph-node-negative cancer. Patients with MAI scores categorized as less than 10 had significantly greater overall survival and significantly reduced risk of a cancer recurrence compared to patients with MAI scores categorized as 10 or greater.
Eighty-five percent of lymph-node-negative patients with MAI less than 10 had a 10-year recurrence-free survival, compared with only 63% for those with MAI 10 or greater. Women with lymph-node-negative breast cancer and an MAI score of 10 or greater had similar survival and recurrence rates as women with lymph-node-positive breast cancer.
The researchers concluded that MAI is a powerful predictor of the risk of a cancer recurrence and survival in women with lymph-node-negative breast cancer who do not receive chemotherapy. They specifically stated, “The MAI is the strongest, most widely available, easily assessable, inexpensive, well-reproducible prognosticator and is well suited to routinely differentiate between high- and low-risk LN-negative breast cancer patients younger than 55 years.” Patients with lymph-node-negative breast cancer currently considering the risks and benefits of chemotherapy may wish to discuss the possibility of MAI testing or the risks and benefits of participating in a clinical trial further evaluating MAI or other prognostic variables with their physician. Two sources of information regarding ongoing clinical trials include the National Cancer Institute (www.cancer.gov) and www.cancerconsultants.com.
Reference: Baak J, van Diest P, Voorhorst F, et al. Prospective Multicenter Validation of the Independent Prognostic Value of the Mitotic Activity Index in Lymph Node–Negative Breast Cancer Patients Younger Than 55 Years. Journal of Clinical Oncology. 2005;23: 5993-6001.
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