Short answers, pulled from the story.
Lung cancer is caused by genetic damage to the DNA of lung cells, most often from cigarette smoking, which causes 80% to 90% of cases. The remainder come from exposure to hazardous substances like asbestos and radon gas, or from genetic mutations that arise by chance.
Lung cancer is the most diagnosed and deadliest cancer worldwide. In 2020 there were 2.2 million new cases and 1.8 million deaths, representing 18% of all cancer deaths.
Small-cell lung cancer makes up around 15% of cases and its cells appear small with ill-defined boundaries. Non-small-cell lung cancer makes up the remaining 85% and includes adenocarcinomas, squamous-cell carcinomas, and large-cell carcinomas, which progress and respond to treatment differently.
Around 19% of people diagnosed with lung cancer survive five years from diagnosis. Survival is much higher at the earliest stage, IA1, at 92% over five years, and drops to 0% at the most advanced stage, IVB. Five-year survival is higher in women, at 22%, than in men, at 16%.
A definitive diagnosis of lung cancer requires a biopsy of the suspected tissue examined under a microscope by a pathologist for cancer cells. Imaging tests such as a chest X-ray, CT, PET, and MRI are used to find tumors and assess how far the cancer has spread.
In 1962 the United Kingdom's Royal College of Physicians concluded that cigarette smoking causes lung cancer. The United States Surgeon General's advisory committee report, published in January 1964, found that cigarette smoking far outweighs all other factors in causing lung cancer.
The United States Preventive Services Task Force recommends yearly low-dose CT screening for people between 55 and 80 with a smoking history of at least 30 pack-years. Regular low-dose CT scans in high-risk people reduce total lung cancer deaths by as much as 20%.