SUNDAY, June 1 (HealthDay News) -- Colon cancer patients who
have the normal version of a particular gene are more likely to
benefit from a combination treatment that includes adding the
targeted therapy Erbitux to chemotherapy.
Some two-thirds of colon cancer patients have the normal, or
"wild-type" form of the gene, according to the new study.
"These findings are very important for patients and also for
clinicians, as we have shown that, using this KRAS test, we can
predict which patients will benefit and which will not benefit from
cetuximab [Erbitux]," said study author Dr. Eric van Cutsem, a
professor at University Hospital Gasthuisberg in Leuven, Belgium.
"We have shown that the activity of cetuximab is confined to the
patients with the KRAS wild-type tumor so, if we know in advance
that a patient has the mutation, we know that we don't have to
treat them with cetuximab."
Van Cutsem spoke at a news conference Sunday at the American
Society of Clinical Oncology in Chicago, where he also presented
his results.
The test is already widely available. Last week, European
authorities approved adding Erbitux to chemotherapy but only in
patients with the normal version of the gene, van Cutsem said.
"We're moving towards tailored or personalized therapy for
patients," said Dr. John Kauh, an assistant professor of hematology
and medical oncology at Emory's Winship Cancer Institute in
Atlanta. "We've always known that tumors are highly heterogeneous.
We are now just beginning to see with the data that we can
basically take a patient's tumor, test it, and see if Patient A
should get cetuximab and whether Patient B should not, and maybe,
for that patient, it may be better."
Earlier results from the same trial presented at last year's
meeting found a 15 percent reduction in risk in patients treated
with the combination therapy as opposed to chemotherapy alone.
Since that time, the biology of KRAS has become better
understood, and other studies have shown the value of the
combination treatment as a third-line treatment. "Those with the
KRAS mutation were resistant to cetuximab in third-line treatment,"
van Cutsem said.
Results were even clearer in the current set of findings, culled
from tumor samples from 587 patients. Those with normal KRAS genes
had a 32 percent reduced risk of developing a recurrence during the
study period, compared with a 15 percent reduction for all
patients.
"At one year, progression-free survival was 25 percent for those
[taking chemotherapy alone] and 43 percent in the combination
group," van Cutsem said. "In KRAS-mutant patients, there was no
difference."
Also, 59.3 percent of normal gene patients responded to the
combination treatment (tumors shrank by more than half), while only
43.2 percent of those on chemo alone responded. There were no
differences in response rates among those with the mutation.
The study looked only at first-line treatment in patients with
colorectal cancer which had already spread to other parts of their
body. Side effects were "manageable," van Cutsem said.
"This is an exciting area of targeted agents," said Dr. Julie
Gralow, moderator of the news conference at which the findings were
presented and director of breast oncology at the University of
Washington and Fred Hutchinson Cancer Center in Seattle. "The
question is, how are we going to able to afford these drugs in
these patients? It's exciting that KRAS seems to predict who will
benefit. The wild-type is two-thirds of patients who will benefit.
We don't need to give this drug to the other third now."
More information
The
American Cancer Society has more on colon and
rectum cancer.
