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For some African Americans, light smokers may not have lower lung cancer risk than heavy ones

CigaretteAlthough the relationship between smoking and lung cancer has been established beyond any doubt, it's still difficult to know how a patient's ethnicity might play into risk assessment. But it's clear that it has a role. Lung cancer is the leading cause of cancer death in this country, and it disproportionately affects African Americans. Doctors are struggling to understand the interactions between genes and environment that contribute to lung cancer risk in all populations.

Physician scientist Sean David, MD, DPhil, and a multidisciplinary team of colleagues recently published in EBioMedicine the results of a study suggesting that African Americans who carry a panel of risky genetic sequences may be at higher risk for the disease, even if they are light smokers.

The study involved analyses of more than 7,000 Women’s Health Initiative participants and nearly 2,000 participants in a lung cancer case-control study with collaborators from multiple institutions in the United States.

As David explained to me in an email:

All smokers are at heightened risk for lung cancer, particularly those possessing high-risk genotypes. Our study suggests that African American light smokers are not at lower risk than heavy smokers if they possess certain genotypes, but that smoking more cigarettes does markedly increase lung cancer risk in individuals without these high-risk genotypes. These conclusions reinforce the message that light or heavy smoking is a risky proposition for African Americans, who can benefit from smoking cessation and evidence-based lung cancer screening services.

The researchers identified six nucleotide changes that appeared to affect the relationship between cigarettes smoked per day and lung cancer risk in African American smokers - all on chromosome 15. Although the nucleotide changes, called single nucleotide polymorphisms, or SNPs, had been associated with lung cancer risk in previous studies, this is the first time the risk has been tied to daily cigarette exposure in African Americans.

Although more research needs to be done to learn how ethnicity and genotype affect a person's lifetime risk for lung cancer, David hopes that the study may help clinicians in their efforts to help all their patients reduce or cease smoking. Stopping cancer before it starts is an important component of Stanford's focus on precision health, the goal of which is to anticipate and prevent disease in the healthy and precisely diagnose and treat it in the ill.

As David explained:

A long term goal is to enable enhanced screening and smoking cessation tools for precision medicine in order to reduce tobacco-related disease and death in African-Americans. We previously reported relationships between one SNP and the average number of cigarettes per day and smoking cessation in two recent papers. The present work translates those investigations into an important health outcome. Future work will employ a combination of basic science and bioinformatics to better understand mechanisms and to pursue validated genetic risk tools and more precise smoking cessation treatments.

David conducted the study with prevention research specialist Marcia Stefanick, PhD, in the Stanford Prevention Research Center.

Previously: Is a proposed ban on smoking in public housing fair?Obesity and smoking together may decrease taste of fat and sweet but increase consumption and Teens these days: smoking less, but engaging in other risky behaviors
Photo by Raul Lieberwirth

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