Aggressive Treatment May Save Female Smokers' Lives
Most Americans think that smoking causes lung cancer and that lung cancer can kill. No one at HSPH would argue this, although they might add that this is a simplification.
Heather Nelson, research associate in the Department of Cancer Cell Biology, has spent much of the last several years probing beyond the simplified explanation of the smoking/lung cancer connection. She has been looking at one form of lung canceradenocarcinomathat accounts for 40% of lung cancers, and one mutation of this form--K-ras--that occurs in 30% of adenocarcinomas.
Every HSPH student hopes his or her thesis will be an important contribution
to the public health endeavor. Heather Nelson took a year to expand upon
her thesis for these important findings.
What she and her colleagues have found is that this particular type of cancer, making up 10% of all cases, is particularly harmful, is only present in current or former smokers, and is three times more likely to affect women than men.
These findings have profound implications for the treatment of lung cancer. Surgery is the therapy of choice for patients who have been diagnosed early in their cancer; radiation therapy and/or chemotherapy are reserved for those in later stages of the disease.
Nelson found that patients with the K-ras mutation who received surgery and who had no clinical evidence of metastasis were four times more likely to die than were lung cancer patients without the mutation. She suggests that patients undergoing surgery could be screened for the mutation. "If K-ras is found," she said, "the patients may benefit from receiving the more aggressive radiation therapy or chemotherapy immediately."
The K-ras mutation was found exclusively in smokers, including patients who had quit smoking earlier in their lives.
At this point, the researchers can only hypothesize why women are at such greater risk. "The mutation seems to be a two step process," said Nelson. "The first step is exposure to tobacco smoke, which causes the mutation itself. Because of the differences we found between women and men, we suspect that effects of estrogen may be a second step that enhances the growth of cells with the mutation."
This research is published in the December issue of the Journal of the National Cancer Institute as "Implications and Prognostic Value of K-ras Mutation for Early Stage Lung Cancer in Women." An earlier version of the research served as Nelson's thesis at the school. She received her PhD in 1998 through the Biology in Public Health program.
Nelson is now turning her attention to non-melanoma skin cancers. She
recently received a million-dollar, four-year grant to look into genetic
traits that might affect the risk of skin cancer and to look at specific
mutations, similar to what she's done with lung cancer. One big difference,
she said, is that she doesn't have to look at survival rates because most
people don't die from non-melanoma skin cancer.
See Also: Cancer-Causing
Mutation Strikes Women Smokers at Three Times the Rate of Men --
press release of November 30, 1999.
