Twenty pack-years is a significant exposure, enough to increase your risk of lung cancer. The risk diminishes over time, following smoking cessation, but will always remain higher than the risk of someone who has never smoked. There are a number of genes that can occur in a variety of forms. Some forms are associated with an increased risk of lung cancer, one example of which is called tumor suppressor gene TP53. When present, this gene variant increases the risk of lung cancer, especially the risk for small cell lung cancer. Your mother may or may not have this gene variant but that doesn’t mean that you have it. And, if you do have it, the increased risk, in no way, means that you will get lung cancer, small cell or other, especially now that you have quit smoking.
The role of lung cancer screening tests is still not clear. Some studies have led to earlier detection of lung cancer but shown little or no effect on overall cancer survival. Still, I favor attempts at early detection, especially during the first ten years following smoking cessation, especially the technique of sputum cytology. That is the examination of coughed-up sputum, for cancer cells. I suggest that you contact your local American Lung Association (ALA) for information about where such testing is available in your community. And, you might want to combine this testing with regular chest x-rays, every 1 to 2 years. Once again, the evidence for value of this testing is not strong but these are easy, non-invasive, inexpensive tests that could offer you the advantage of earlier detection than otherwise would be the case, without screening.