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Blood Test May Give Early Warning of Colorectal Cancer


Careful attention to the results of routine blood tests may provide an early warning of potential colorectal cancer. That’s the word from researchers at Tel Aviv University, who say signs of anemia may be a warning signal for this common form of cancer.

Colorectal Cancer

An estimated 102,900 new cases of colon cancer and 39,670 new cases or rectal cancer will be diagnosed in the United States in 2010, according to the American Cancer Society. Excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in men and women when they are considered separately, and the second leading cause when they are combined. More than 51,000 adults are expected to die of the disease in 2010.

People who have colorectal cancer typically have anemia, characterized by low levels of hemoglobin, the oxygen-carrying, iron-containing factor in red blood cells. Rather than be viewed as a symptom of active disease, however, researchers at Tel Aviv University have found that signs of anemia may serve as a screening tool for colorectal cancer.

This would be a significant finding, as current screening methods are allowing polyps to be found earlier when the disease is easier to cure. The addition of another, more effective screening tool could make cancer detection even more efficient and ultimately result in saving more lives.

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Colorectal Cancer Screening Tool
Researchers at Tel Aviv University evaluated blood test data spanning ten years from more than 3,000 individuals with colorectal cancer and compared them with 10,000 controls without the disease. They found that most patients who have colon cancer have a history of consistently declining hemoglobin levels up to four years before they are diagnosed with the disease. Specifically, a declining trend of more than 0.28 grams per deciliter every six months over four years was documented.

This study represents the first time scientists have quantified the correlation between anemia and colorectal cancer and a decline in hemoglobin levels. According to graduate student Inbal Goldshtein, one of the study’s authors, continuous declines in hemoglobin levels in individuals have gone largely unnoticed by clinicians, who typically look for large drops in blood test results.

“But this is not accurate enough,” according to Goldshtein. “It is important to look at the continuing trend of each individual. If a person experiences a consistent decline relative to his own average level, it may be cause for concern.”

In the new study, participants who had colorectal cancer demonstrated a sharp drop in hemoglobin levels. However, because the declines were not outside what is considered to be normal, doctors had not suspected colorectal cancer was on the horizon.

The study’s authors point out that observing a gradual decline in hemoglobin levels is a screening tool that can be part of a typical physical examination. Compared with current testing for colorectal cancer, which is unpleasant and costly, a routine blood test is convenient. The next step is the creation of an algorithm that will automatically identify declining, “red flag” hemoglobin levels.

American Cancer Society
Tel Aviv University