Three groups of scientists have independently identified two genetic variations in chromosome 15 as a major reason for developing lung cancer. They however hold differing opinion as to whether the variation causes the disease directly or by increasing addiction to cigarettes.

Their study is in sharp contrast to the popular notion that smoking is the major, if not the only reason behind lung cancer.

The M.D. Anderson Cancer Center team lead by Dr. Christopher Amos, Ph.D. (studied 5,778 persons with lung cancer and 4,831 controls, who were matched by smoking status) and the team at International Agency for Research on Cancer in Lyons, France, lead by Paul Brennan, Ph.D. (4,502 cases and 7,377 controls) found at best a modest association with smoking behavior.

On the other hand Dr. Kari Stefansson, M.D., of Iceland’s DeCODE Genetics, said he and his colleagues found a clear link with increased smoking and difficulty quitting, which in turn contributed to smoking-related diseases like lung cancer and peripheral artery disease.

“The association is very solid, the P-values are vanishingly small, and the sample size that we are looking at was very large,” Dr. Stefansson said. The associations with lung cancer and peripheral artery disease were significant at P=1.5×10-8 and P=1.4×10-7, respectively. They had a large sample size of 13, 945 smokers.

What all researchers agree on is that a region on chromosome 15 contains genetic variants that are relatively common in the population and they are linked, directly or indirectly, to lung cancer.

Having one copy of the variant increases the risk of disease by about 30% and having two copies increases the risk by about 80%, the researchers said.
Source: Nature [www.nature.com/nature/journal/v452/n7187/abs/nature06846.html]