Not All Colon Cancer Patients Need Chemother...( DNA mismatch in some early stage case...),Health

DNA mismatch in some early stage cases makes therapy of little benefit, shortens survival

FRIDAY, May 16 (HealthDay News) -- Colon cancer patients with a specific subset of the disease don't need to receive chemotherapy. In fact, not only does chemotherapy not benefit this group of patients, it may actually harm them, a new study found.

"If you are found to have [this type of colon cancer], then you should not be treated with chemotherapy. Surgery alone would be standard treatment," said Daniel Sargent, lead author of the study and a professor of biostatistics at the Mayo Clinic in Rochester, Minn.

"In our data, patients who have [this type of cancer] who had surgery alone had a 93 percent survival at five years. In our study, chemotherapy actually lowered survival to 75 percent. So, we have a group of patients who can be spared the toxicity, the expense and the inconvenience of treatment and have a very good outcome even without any [chemotherapy] treatment," Sargent said.

The findings, presented Thursday at the American Society of Clinical Oncology annual meeting, in Chicago, confirm previous research and now give physicians a clearer roadmap for treatment, the study authors said.

About 15 percent of colon cancer tumors are known as deficient DNA mismatch repair (dMMR) tumors, because they have lost the ability to repair DNA damage. This particular type of tumor seems to be less aggressive than other forms of colon cancer, the researchers said.

A study published by the same group of researchers in 2003 in the New England Journal of Medicine also found that this subset of patients did not benefit from standard chemotherapy for colon cancer. Because the finding was so novel, the results needed confirmation before they could be incorporated into clinical practice. This new study offers that confirmation, the researchers said.

"We're talking about patients with early stage colon c
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