One of the principles of screening is that the likelihood of detecting a cancer depends greatly on the risk that a person being screen has for developing that cancer. Low risk means that it is very likely that any abnormality that is detected is more likely to be unrelated to cancer. And because of that, nearly all of the screening efforts thus far have focused on patients with a significant smoking history.
Though the topic of never-smokers with lung cancer is a particular focus of my interest and research, and there has been a greater focus on this topic in the last few years, most lung cancer is still related to smoking. However, we have clearly reached a point where the majority of people diagnosed with lung cancer are not current smokers at the time of their diagnosis, and about 60% have quit at some point. Many of these patients, and their families and friends, express surprise that they developed lung cancer, especially if someone had quit 20 or 30 years prior.
My name is Robert Resta, and I'm a certified genetic counselor working at the Hereditary Cancer Clinic at Swedish Cancer Institute in Seattle. Dr. West asked me if I might provide a few general comments about the genetic contribution of lung cancer.
Radon is a product of the decay of naturally occuring uranium in the earth, and it's estimated to be responsible for perhaps 2-3% of lung cancers overall. In one reference (here) doesn't offer any details of where the numbers come from, an estimated 26% of lung cancer in never-smokers is caused by radon:
It has been noted for many years that Asian women appear to be particularly predisposed to lung cancer despite a low frequency of smoking. Many of the series from resected NSCLC series have never-smoker rates of 30-50%, with the majority of these never-smokers as women. As we've struggled to understand and explain risks, hormonal differences between men and women have emerged as a possibility, as has genetic differences.
Among the key issues in following patients with a history of treated lung cancer is the pattern of recurrence. We need to have a sense of when the risk is highest and where people are more likely to demonstrate new evidence of disease. Fortunately, there are several studies that can help us with these questions.
Many members have asked questions about increased risk of lung cancer among family members of people who have developed lung cancer. Overall, I have not highlighted this, partly because we don't tend to highlight genetics as a major contributor of lung cancer risk. But the fact is that 10-15% of people who develop lung cancer never smoked, and the vast majority of smokers never develop lung cancer.
In light of a growing focus on the issue of lung cancer in never-smokers, it makes sense to try to identify potential causes in this population. Among the leading candidates as a cause of lung cancer in never-smokers is secondhand, or environmental tobacco smoke (ETS) exposure.
In addition to risk for having a recurrence of a lung cancer that has been surgically removed, patients with a history of early NSCLC are also at risk for a second primary (unrelated to the first) lung cancer. In other words, having had a lung cancer, even if it was cured, means that a person remains at higher risk for a new lung cancer than people who never had a lung cancer.