What is the average survival rate for small cell lung cancer after chemo and radiation therapy?

Depends: Localized or extensive. Localized has a 5 year survival of around 30-40%. Extensive has much worse odds.

Depends on stage : Treated limited stage has a median survival over a year and have about 5% survivors at 5 years extensive stage has about 9 months of median survival.

>25 %: In a large randomized study testing radiotherapy and chemotherapy for non-metastatic small cell lung cancer, ~ 25% of patients were alive after 5 years. Since then, advances in imaging, treatment techniques, and supportive care may have increased this rate slightly.