Genetic Key to Lung Cancer Drug Success Found
Genetic Screening May Allow Targeted, Effective Lung Cancer Treatment
April 30, 2004 -- A new discovery may soon allow doctors to
target lung cancer therapy based on a person's genetic profile.
Lung cancer is the leading cause of cancer death in the U.S.,
and until now no effective treatments have been available for the disease. A
recently approved drug, Iressa, is thought to be the first drug to work well
against lung cancer, but the problem is that it works only in a small number of
However, two new studies show that genetic screening may help
doctors identify which lung cancer patients will respond well to the drug as a
first line of treatment. Researchers found people with non-small-cell lung
cancer that had an abnormal gene for the epidermal growth factor receptor
(EGFR) benefited dramatically from treatment with Iressa.
Non-small-cell lung cancer accounts for the majority of lung
cancer cases and deaths. In people with this type of cancer, EGF (epidermal
growth factor) causes cells to grow and form a solid tumor.
"We know that many lung cancers have elevated EGFR
expressions, but only a few thus far have been shown to respond to Iressa,"
says Harmon Eyre, MD, chief medical officer of the American Cancer Society, in
a news release. "This study indicates potentially better outcomes for 10 to
15 percent of those diagnosed with non-small cell lung cancer, primarily
non-smoking women, and while it may not have a huge impact in terms of sheer
numbers, it is a major step."
The findings appear in this week's issue of the journal
Science and in an upcoming issue of The New England Journal of
Targeted Lung Cancer Therapies Now a Possibility
In the studies, researchers compared the genetic makeup of lung
cancer tumors extracted from people who were treated with Iressa, including
those who had responded well to the drug and those that didn't.
They found those that had responded well to the drug were much
more likely to share the same genetic mutation of the EGFR gene. For example,
Thomas Lynch, MD, and colleagues at Harvard Medical School, reported in
NEJM that eight of nine patients who were successfully treated with the
drug had the mutation while none of the seven that didn't respond to the drug
In an editorial that accompanies Lynch's study, Mark R. Green,
MD, of the Medical University of South Carolina, says that even if less than
10% of lung cancer patients are eligible for treatment with Iressa the impact
will be significant because more than 1 million people are diagnosed with this
deadly form of cancer each year.
If confirmed by further studies, Green says this research
"will fundamentally change targeted therapy for solid tumors."
Although more studies are needed to confirm these results, J.
Guillermo Paez, PhD, of the Dana-Farber Cancer Institute in Boston, and
colleagues report in Science that identification of EGFR mutations in
other types of tumors may also lead to more effective, targeted treatments for
a variety of cancers.