According to WebMD.com:
"To qualify as remission, your tumor either doesn't grow back or stays the same size for a month after you finish treatments. A complete remission means no signs of the disease show up on any tests. That doesn't mean your cancer is gone forever. You can still have cancer cells somewhere in your body."

We all know, most oncologists wait 2-3 months after completion before doing scans to determine the effectiveness of a treatment plan. Also, there has to be some positive change in the size or appearance of the tumor(s) on the PET scan, such as lack of FDG uptake/reflectivity.

Some oncologists will say the patient is cured if they stay in complete remission for 5 years. This does not mean a different cancer won't show up later.

Cancer can come back after 5 years. The hospital you go to has the have the ability to do many tests, every 3-4 months for 5 years, then annually thereafter. People who have had lung cancer are at higher risk of developing a second cancer, so testing is important for the rest of your life. Early diagnosis is very important. I personally think everyone should get a chest scan around age 60. We did routine scans for breast cancer, and colon cancer, why not lung cancer as the fatality is so high? Our medical system it not uniform in preventing cancer. Smokers are at higher risk, as is family history.

Cancer is not random at all. You just listed 7 risk factors for lung cancer. Plus there is family history and concurrent diseases. I am surprised people are living so long!

I agree that there are are many reasons for cancer, toxins, smoking, DNA, other unknown things. Given that lung cancer is so serious I think everyone should get a CT scan about age 60. It only takes 10 minutes; it is the machine costs that hold things back. Plus our wacko insurance costs.

A lot of cancers are caused by air pollution, other toxic carcinogens found in water, industrial food, lifestyle, hormonal imbalance, etc ...
The stigma that smokers get lung cancer need to be put aside. At that point, early detection tests will be able done automatically.