TUESDAY, Oct. 26 (HealthDay News) -- New research challenges
previous assumptions about how to treat metastatic colon cancer in
patients with a certain genetic mutation.
While guidelines have recommended that people with this type of
cancer and mutations in their KRAS gene should
not receive the targeted therapy cetuximab (Erbitux), a new
study finds that a subset of these patients might actually benefit
from taking the drug.
"Those drugs [cetuximab and its sister medication, panitumumab (Vectibix)] have been shown in a number of other studies to be less effective in patients who have mutations of the KRAS gene," explained Dr. Durado Brooks, director of colorectal cancer at the American Cancer Society. "Those studies have been so convincing that the National Comprehensive Cancer Network [which produces treatment guidelines] added KRAS testing as an element of decision-making for using these drugs to determine whether or not these drugs are likely to be useful."
This new study, appearing in the Oct. 27 issue of the
Journal of the American Medical Association, suggests that researchers and clinicians both may need to drill down further in attempting to decipher which patients will benefit most from different targeted therapies.
"Before, we have been lumping [different] KRAS mutations together," Brooks said. "This current article is saying we may have been overly simplistic in our approach."
"It's a provocative report," added Dr. Steven Cohen, a medical oncologist with Fox Chase Cancer Center in Philadelphia. "The mantra has been to lump [the two KRAS] mutations together. This gives us reason to second-guess ourselves that we should not be excluding patients [with this one mutation] from this type of treatment."
Here, a group of European researchers looked at 579 patients for
whom chemotherapy had not worked and who had taken cetuximab in
previous clinical trials.
For the analysis, patients were separated out, depending on
whether they had the KRAS codon 12 mutation or the KRAS codon 13
Patients with the KRAS codon 13 mutation who were treated with
cetuximab lived an average of 7.6 months, versus 5.7 months in
those with the other mutation. Also, an average of four months
transpired before disease progression, versus about two months in
the control group, the investigators found.
Those with the KRAS codon 13 mutation didn't respond as well to
the drug as people with a normal version of the gene, but they
While some experts may quibble with the study's methodology --
pooling data from several already-completed trials -- this may be
the only way that enough patients with this relatively rare (codon
13) mutation could be collected for a legitimate analysis, Cohen
Maybe 5 percent of patients with metastatic colorectal cancer,
which is cancer that has spread, have this particular KRAS
mutation, Cohen said.
Not only will more research need to be done before giving
cetuximab to people with the codon 13 mutation becomes common
practice, but doctors, the cancer network and insurance companies
will have to get on board, Cohen noted.
The cost of cetuximab can be $3,000 a week or higher (the
treatment is delivered weekly).
"It's a major cost issue," Cohen said.
U.S. National Cancer Institute has more on
treatments for colorectal cancer.