Breast tumor markers � are they useful?
by: Mai Brooks
Breast cancer
is the most common form of cancer in women and the second leading
cause of cancer deaths in American women. In 2009, approximately
194,280 patients are estimated to be diagnosed with invasive breast
cancer, and 62,280 with carcinoma in situ. An estimated 40,610 will
die of this disease. For a woman of average risk, the lifetime
incidence of breast cancer is one in eight.
Serum tumor markers for breast cancer used in the clinic include CA
15-3, CEA (carcinoembyonic antigen), and CA 27-29. All have low
sensitivity and specificity, and thus not helpful in detecting early
breast cancer. CA 15-3 levels are increased in approximately 5-30%
of patients with stage 1 disease, 15-50% with stage 2, 60-70% with
stage 3, and 65-90% with stage 4. CA 15-3 measurements are also
elevated in 15-20% of women with benign breast conditions, 50-60%
with liver disease, 20-70% pulmonary malignancies, 15-60% of
gastrointestinal/colonic malignancies, and 40-60% of ovarian cancer
cases. CEA is more prevalent in colorectal cancer, whereas CA 27-29
is more specific for breast cancer. These three tumor markers have,
however, been validated for monitoring treatment in patients with
advanced disease, particularly if the cancer cannot be evaluated
with conventional imaging. The American Society of Clinical Oncology
recommends the use of CEA, CA 15-3 and CA 27-29 only in metastatic
settings, whereas the European Group on Tumor Markers recommends
their use in disease surveillance in general.
With the current technology, circulating tumor cells have been found
in very few cases of early stage breast cancer. Circulating tumor
cells detected in both localized and metastatic breast cancer
patients have been associated with worse outcome. Circulating tumor
cells may also predict response to therapy.
There is much ongoing research to investigate new biomarkers for
early detection of breast cancer. Blood-based markers include cells,
DNA, RNA, peptides, sugars, and autoantibodies. Breast-based markers
such as nipple/ductal fluid and breast fine needle aspiration (FNA)
also include cells, DNA, RNA, proteins, sugars, and autoantibodies.
In the future, it is likely that a combination approach to measure
simultaneously multiple markers would be most successful in
detecting early breast cancer. Ideally, such a biomarker panel
should be able to detect breast cancer in asymptomatic patients, and
improve the accuracy of screening mammograms. A reliable biomarker
signature may also signify new breast cancer, even in the setting of
normal mammogram and physical examination, and would indicate
further more intensive diagnostic workup and/or preventive
treatment.
Dr. Mai Brooks is a surgical oncologist/general surgeon, with expertise in early detection and prevention of cancer. More at http://www.drbrooksmd.com, http://thecancerexperience.wordpress.com and http://progressreportoncancer.wordpress.com.
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