@acguidon, The question of what caused our cancer can consume us, and unfortunately, most of us will likely never know what caused our lung cancers. I'm not an expert, but I believe the pathology of the cancer can point to asbestos exposure in the form of mesothelioma. There are many types of lung cancer, and some have no known causes. We are exposed to all sorts of toxins throughout our lives. We also know that each day as cells are replicated within our bodies, mistakes are made in that replication process, usually our immune systems account for those mistakes and kill off the mutated cells. Sometimes that doesn't happen as it should.
Someone told me, "biology makes mistakes". It may not be anything that you did or were exposed too, sometimes the biology of our bodies makes mistakes. That's hard to accept when we want answers.
You were diagnosed about 2 years ago, how are you doing now?