When people spoke of stage 4 lung cancer survival rates, it is impossible to predict how long someone will live with their cancer. The statistics apply only to averages, which consists of more living and less time living.
Some have stage 4 inoperable lung cancer. Less than 5 in 100 people (less than 5%) diagnosed with stage 4 non-small cell lung cancer live for at least 5 years. My guess was perhaps only a year with palliative chemotherapy.