NEW YORK (Reuters Health) - Researchers have confirmed yet another ill effect of smoking cigarettes: it increases the risk of breast cancer in women with a common genetic variation.
The gene involved, N-acetyltransferase 2 (NAT2), is believed to help clear the body of aromatic amines, a major carcinogen in tobacco smoke. The researchers found that women with the slower-acting form of this gene -- who represent 50 percent to 60 percent of the white population and 35 percent to 40 percent of African-Americans -- are more likely to get breast cancer if they smoke.
But the study's lead author said the finding shouldn't motivate people to undergo; instead, she said, it should spur them to quit smoking. "We still know very little about what these genes do and how they might affect risk-we think the most important thing for people to do is to live a healthy lifestyle," Dr. Christine B. Ambrosone of the Roswell Park Cancer Institute in Buffalo, New York, told Reuters Health.
It has been known for years, Ambrosone noted, that the risk of bladder cancer is higher in people with the slow-acting gene version, known as the slow acetylator NAT2 genotype. However, research to date has not found any link between cigarette smoking and overall breast cancer risk. Scientists had theorized that smoking might actually reduce breast cancer risk because it can lower estrogen levels.
To investigate whether the presence of genetic mutations may influence the smoking-breast cancer relationship, Ambrosone and her colleagues analyzed data from 13 studies including a total of 11,922 women.
For women with the slow-acting gene, the researchers found, breast cancer risk increased with the number of pack years smoked, but smoking had no effect on breast cancer risk in women with the fast-acting genotype.
However, women with the slow-acting gene who smoked for at least 20 pack years -- the equivalent of a pack a day for 20 years --were 44 percent more likely to develop breast cancer than non-smokers. Theis iIncreased risk was seen for both premenopausal and postmenopausal women with the slow acetylator NAT2 gene.
"Because of the frequency of slow acetylator genotypes among non-Asian populations...smoking cessation programs need to be further targeted to women as a means for preventing breast cancer," Ambrosone and her colleagues conclude.
"What we believe is important is the public health message," the researcher said. "Here's one more adverse health outcome that smoking is likely related to."
SOURCE: Cancer Epidemiology, Biomarkers and Prevention, January 2008.
Much research has shown an association between smoking and higher breast cancer risk. The study reviewed here found that breast cancer risk is higher in women who smoke AND who have a slow-acting form of a particular gene, NAT2.
Slow-acting NAT2 is found in 50% to 60% of white women and 35% to 40% of African American women. The slow-acting form of NAT2 slows the body's ability to get rid of aromatic amines, the cancer-causing substances in cigarette smoke. In this study, women who smoked but DIDN'T have the slow-acting NAT2 gene had the same breast cancer risk as women who didn't smoke.
This study suggests that smoking may not increase breast cancer risk in women who don't have the slow-acting NAT2 gene. But there isn't a routine test for the slow-acting NAT2 gene. Even if you have the fast-acting version of NAT2, smoking is a bad idea. Smoking can harm your heart and lungs and put your overall health at risk.
If you don't smoke, don't start. If you do smoke, get help and find a way to quit. It's tough, but definitely worth it. The American Lung Association offers a free online smoking cessation program. Local chapters of the American Cancer Society offer their Fresh Start program to help people quit smoking. You can also call their "quitline" at 1-800-ACS-2345, to get support and free advice on how to stop smoking from trained counselors.
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