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Tumor Markers
Tumor markers are an oncological method of diagnosing cancer. These markers are most commonly found in body fluids such as blood and urine. Far from being a definitive diagnosis for cancer, tumor markers are typically only helpful in assisting in diagnosis. Many common tumor markers can be caused by non-cancerous tumors, or various other causes, thus making tumor markers not a certain diagnosis method.
While a biopsy is usually the best method to determine the presence of cancer, the possible presence of tumor markers in both malignant and benign tumors can enhance the effectiveness of a biopsy. It is still unknown whether tumor markers can be used for early detection of cancer, as most doctors feel that the markers are not specific enough to be utilized in early detection situations. Some tumor markers can be indicative of the aggressiveness of some cancers.
In addition to being used for diagnosis, tumor markers can be helpful in evaluating patient response to treatment. When marker levels decrease, it can be a sign of positive response to treatment. Conversely, if marker levels increase, not only can it be a sign of non-responsiveness to treatment, it can also be a sign of recurrence in patients who are in treatment. However, there are occasions where markers increase when a tumor is quickly destroyed by treatment, so an increase in markers could possibly signify a positive response to treatment.
The use of tumor markers began in 1965, with a study of patients suffering from colon cancer. Throughout the 1970’s, researchers began to look for various tumor markers. The research has proven to be difficult at times, as identifying certain proteins as tumor markers is not an easy task because many alternate health issues can raise various protein levels. It was hoped that tumor markers would be useful for early diagnosis; however, research soon showed that most tumor markers occured only after significant presence of cancer.
Tumor markers are most often identified as proteins in the blood, urine or tissue. To identify them, antibodies to various proteins are introduced to the blood, urine or tissue, and any reaction is noted. Abnormal levels of particular proteins can be linked to certain kinds of cancers. There are over a dozen specific markers known to doctors, and continuing research is going into discovering new markers. Using DNA analysis, doctors are learning new gene patterns that can be found in tumor markers.
Some of the more common markers used by doctors include a prostate-specific antigen. Although the presence of the antigen can vary dramatically from patient to patient, recent developments in the science of testing has made diagnosis using the antigen more accurate. Another common marker used by doctors is a marker present in former breast cancer patients. However, the marker usually does not rise significantly until the cancer has already shown other major signs.
Since tests for tumor markers are not specific, nor sensitive enough
for early diagnosis, scientists are continuing work on developing ways
to identify gene expressions in certain markers. The ability to find certain
gene patterns that manifest themselves in various markers could make the
tests more accurate and useful. See also section
on immunohistochemical markers for mesothelioma.
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