Most individuals diagnosed with relatively early, stage II colon cancer (representing 25 to 30 percent of all cases) can be cured with surgery alone. A small minority benefit from added chemo.
But, Kerr said, "there's no clear consensus on how to select patients" who might gain from this additional chemotherapy, and weed out those who would not.
The research team started out by analyzing almost 800 genes from almost 1,900 colon cancer patients. They then tested an initial, promising gene signature in about 1,500 patients. Half of these individuals received chemo and half did not.
The presence of certain genes was able to predict those with a higher risk of recurrence and those with a lower risk, the team found.
"A seven-gene signature for the first time ever gives a significant prognostic recurrence score," Kerr said. "This allows us to define a population of patients at low risk of recurrence -- about a 10 percent chance of the cancer coming back [in three years] -- in whom I would counsel that chemotherapy would be of very little value indeed."
For the other group, recurrence rates closer to 20 or 25 percent at three years may indicate a benefit to getting chemo, he said.
Doctors already look at "T-stage" of a tumor (is it locally advanced?, etc.) as well as "mismatch repair," which refers to a gene repair mechanism, to predict recurrence. However, according to Kerr, a large group of patients would benefit from this new tool that would not benefit from the two older screens.
"The new tool is an independent important variable," Kerr said. "There would be 70 percent of patients in whom T-stage and mismatch will not be informative and we think that, in this group, the new tool will provide a useful addendum to the clinical decision-making process."
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