May 18 2010
New research shows genes that make smokers more likely to develop chronic obstructive pulmonary disease (COPD), or emphysema, are also closely linked to an increased likelihood of developing lung cancer, according to studies presented today at the American Thoracic Society's annual meeting.
“In our clinical trials we have learned two things about Respiragene”
Research on seven genes critical to determining the lung's response to cigarette smoke in both COPD and lung cancer confirm a strong genetic overlap for susceptibility to both diseases, Dr Robert Young, Associate Professor of Medicine and Molecular Genetics at the University of Auckland, told the meeting. The genes, implicated in inflammation and repair pathways, were studied in current and former smokers.
Together, COPD and lung cancer account for close to half of all smoking-related deaths each year. Past research has suggested that susceptibility to lung cancer is closely tied to COPD, but until now specific genes linking the two diseases have not been well understood, and the clinical utility of this information has been overlooked, Dr Young said.
"Gaining a better understanding of which patients are at greatest risk of premature death or disability, based on their smoking habit and genetic make-up, can help us identify those in urgent need of help while there is still time to prevent lung cancer or diagnose it earlier," said Dr Young.
Lung cancer diagnosis and treatment often comes too late for the approximately 1 in 10 smokers who develop it. By the time symptoms are evident, cancer has often progressed to a point where it becomes very difficult to treat successfully. Survival rates are poor: 80% of those diagnosed with lung cancer die within two years of diagnosis and half are dead within a year. Lung cancer remains the leading cancer killer in the United States and most other developed countries.
Dr Young's research has led to the development of a genetic test for lung cancer risk assessment in current and former smokers called Respiragene ™, which is based on a cheek swab. Respiragene combines a test for 20 specific genetic variants called SNPs (or single nucleotide polymorphisms) linked with lung cancer risk and an assessment of patient clinical factors including age, family history and prior lung disease to derive a score that places current or former smokers into Moderate, High and Very High risk categories.
The utility of the Respiragene score (to be presented on Wednesday in the ATS Seminar "Beyond Pack Years: Who's really at risk of developing lung cancer") has been validated in four separate studies among lung cancer patients in three different countries.
"By including the genetic factors in the lung cancer risk assessment, we are now able to personalize the risk for people who smoke with much more precision than ever before," said Dr Young. "Astonishingly, many smokers still believe that their risk of lung cancer is no greater than that of non-smokers."
Preliminary data from a study of smokers in New Zealand randomly selected to take the Respiragene test suggests it encourages people to stop smoking. The quit rate among participants six months after testing was over 30%. This compares with the 4-5% of smokers overall who manage to give up smoking each year.
"In our clinical trials we have learned two things about Respiragene," said Dr Young. "First of all, it is a popular test - people want to find out their individual risk of lung cancer. It is also proving to be highly motivating in getting people to quit smoking, which is, of course, among the best things anyone can do for their health."
Genetic-based improvements to risk prediction should also prompt closer monitoring of higher risk individuals by their doctors and prioritization for potential screening and earlier lung cancer detection efforts. Such an approach to preventing coronary heart disease has been used by doctors for over 20 years to identify people most at risk and help promote healthier lifestyle choices and target drug therapies, said Dr Young.
"Currently, there are over 400 people a day dying of lung cancer in the US and over 1000 a day in Europe. Nearly 90% of them are current or former smokers," said Dr Young. "Lung cancer is preventable and accounts for 1 in 3 cancer deaths. COPD is soon to be the 3rd leading cause of death in developed countries and worsening - but we can identify the people most at risk from these diseases now."
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