There is no fixed timeline for lung cancer to progress to Stage 4. The pace depends on tumor biology, subtype, genetic drivers, immune response, and a patient’s overall health. NSCLC can be indolent in some individuals and more aggressive in others. Another major factor is diagnostic delay: tumors may be present for a long time without symptoms and only become apparent once they are already advanced. Therefore, the practical focus is less about a universal “how many months” and more about rapid evaluation and timely treatment when warning signs appear. Completing imaging, biopsy, and molecular profiling quickly helps determine stage accurately and enables the most effective therapy to control disease and improve outcomes.