Life expectancy for lung cancer gone to brain. pet scan shows no other cancer now, only 1 tumor on brain. surgery and whole brsin radiation will be?

Factors: Many factors are involved: age, immune system, type of tumor, gender in certain cases, type of chemotherapy , compliance among many others. Your oncologist is the best guide.

Difficult to say.: This is considered an advanced cancer, stage IV or distant metastases stage. As you said, surgery and radiation is the treatment for this. However, as to the outcome, it is difficult to say. The 5 year survival of patients with this stage is <5%, but with just one lesion, and all the advances you never know, so see your doctor/oncologist. Best of luck.

"oligometastatic": Patients with a single brain tumor as the only site of metastatic disease are called "oligometastatic." the chance of cure, though small, is real. Every cancer specialist has a few such patients. I would strongly recommend aggressive treatment, including either radiosurgery (cyberknife, gammaknife, etc.) to the brain or surgical resection, and again stereotactic or chemoradiation to the lung.