The researchers found that about 4 percent of the patients had tumors that didn’t produce CDX2.
In an initial study of 466 patients with any stage of colon cancer, only about 41 percent of those with CDX2-negative tumors lived disease-free for five years after treatment, compared to 74 percent of those with CDX2 in their cancer cells.
Further, patients whose tumor cells didn’t express CDX2 were more likely to benefit from chemotherapy in addition to surgery than were people with CDX2-positive tumors.
About 91 percent of patients with CDX2-negative cancers treated with surgery plus chemotherapy lived disease-free for five years, versus about 56 percent of those who did not receive chemotherapy, the study found.
Because this study did not involve a test on new patients, doctors can’t be certain that this association is valid, Clarke warned.
“The data is extremely strong, but you need a prospective analysis to be 100 percent sure,” he said. “It should be validated in a prospective trial.”
The test could be put into practice right away, given that many laboratories can run this sort of antibody check on colon tumor cells, Clarke and Brawley said.
Brawley agreed that the study does not prove that chemotherapy will improve the outcome of patients with stage 2 colon cancer. “That is still a stretch,” he said.
However, he expects cancer doctors will go ahead and give chemotherapy anyway to patients who are CDX2-negative.
The test likely will be applied only to stage 2 patients, however. That’s because stage 3 colon cancer patients already get chemotherapy alongside surgery, Brawley said.
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