Blood Tests May Spot Colon Cancer
TUESDAY Sept. 22, 2009 -- Simple blood tests may someday become a noninvasive and cost-effective way to detect colon cancer, two new studies suggest.
Researchers were to present studies in Berlin, Germany, on Monday that could offer an alternative to colonoscopy or fecal occult blood tests for diagnosing colorectal cancer, the second leading cause of cancer death in the United States and Europe.
"We have found biomarkers that can be used to screen for colorectal cancer," said Dr. Joost Louwagie, of OncoMethylome Sciences in Liege, Belgium, and lead researcher of one study. "These markers are found in blood, so a regular blood test performed during a regular physical check-up could check for the presence of colorectal cancer."
Louwagie was scheduled to present the finding at the 15th Congress of the European Cancer Organization and 34th Congress of the European Society for Medical Oncology.
For this study, Louwagie's team took blood samples from 193 colon cancer patients and 688 people without colon cancer who were having colonoscopies. The researchers then looked at various genes linked to cancer to find the best ones to distinguish colon cancer.
The researchers found two genes -- SYNE1 and FOXE1 -- were present in abundance in people with colon cancer, but infrequent in those without the disease.
The sensitivity of the test, that is the number cancers it identified, was 58 percent, and the specificity, the proportion of noncancerous patients it identified, was 90 percent. In a second group of patients, specificity was 56 percent and sensitivity was 91 percent.
For patients with early-stage colon cancer, the sensitivity and specificity were lower, at 41 percent and 80 percent respectively, Louwagie noted.
This test will not replace colonoscopy or fecal occult blood tests, the standard tests for colon cancer, but may become another option that many people will find easy and acceptable, Louwagie said. "What we are trying to do is make sure as many people as possible are being screened," he noted.
Coon cancer is striking young patients, so any test that can detect the disease early could be a significant breakthrough, said Dr. Floriano Marchetti, an assistant professor of surgery and director of the Colon and Rectal Surgery Residency Program at the University of Miami Sylvester Comprehensive Cancer Center.
"If such a screening test could reduce deaths from colon cancer it is very significant," Marchetti said. "A noninvasive, inexpensive blood test could get more people to be screened."
More trials are needed to prove the validity of the test, Louwagie said. Currently, the researchers hope to have a trial of some 7,000 people under way by the end of the year.
In a second study, to be presented at the meeting Monday, German researchers developed another blood test to diagnose tumors in patients with colon, rectal or gastric cancers, one they say will also predict the likelihood of metastasis.
The team, led by Ulrike Stein, from the ECRC Charite University of Medicine and the Max-Delbrueck-Centre for Molecular Medicine in Berlin, isolated RNA from the blood of patients with gastrointestinal tumors.
Blood samples were taken from 185 colon cancer patients, 190 rectal cancer patient and 91 gastric cancer patients. Samples were also taken from 51 tumor-free patients. The researchers looked for levels of S100A4 gene, which is known to be a metastasis progressor with diagnostic and prognostic relevance.
"We found that S100A4 mRNA was present at significantly higher levels in the group of cancer patients, no matter whether they had colorectal or gastric cancer, than in the tumor-free control group," Stein said in a statement. "And there were yet higher levels in the patients with metastases than in those where the disease had not yet metastasized."
In addition, patients who developed metastases later had higher S100A4 levels in their initial blood tests than those whose disease did not metastasize, Stein said. "This means that in future we might be able to identify those patients who are likely to develop metastases," she said.
These findings need to be replicated in larger populations, but the test could eventually be used to screen the general population to detect these cancers early, the researchers say.
"We are hoping that, by enabling the identification of those patients whose disease is likely to progress more quickly, we will be able to treat them in the future accordingly by tailoring therapy to their individual needs," Stein said.
Marchetti agreed. "Hopefully, with this screening you will detect a lot more stage I and II cancers than we do now which are likely to become aggressive," he said.
"This study shows, regardless of the stage, if you find an increased level of this gene in patients, even with early cancer, now you will have a reason to treat these patients with chemotherapy and radiation, and potentially cure more patients," Marchetti said.
Colorectal cancer strikes one in 17 people in their lifetime, according to background information provided in the study. Colonoscopy is highly sensitive but invasive, while fecal occult blood tests, which require patients to return stool samples to their doctor, are distasteful to some people. Since blood tests are already part of most physical examinations, a colon cancer blood test might improve screening rates, the researchers said.
Posted: September 2009
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