Lung cancer with no chemo and no radiation at 79 how long to live?

Need more info: Need to know more about the type of cancer (small cell vs. Non-small cell), tumor size and location. Small cell, larger, closer to the center of the chest and metastases all carry a worse prognosis. Consider radiation - it is generally easier to tolerate than chemo and will prolong lifespan, if appropriate to the type and location of the cancer.

Nobody knows: It could be few minutes or a few years depending on type and stage. Your doctor can give you a better estimate.

Depends: type/stage: There are different types of cancer (small cell, non-small cell, thymoma, etc.) and stage (tiny lesion, all over). Generally the smaller it is at first, the more time you have without any therapy. The more widely it has spread, the less time you have. A tiny lesion may leave you with over a year, disease all over the place may only give you weeks. This is impossible to exactly know/answer.