<s>[INST] my mom was diagnosed thyroid CA in 2001.Radiation therapy was done.she is taking thyrax since then.Last Feb. she went to see a Dr. due to pains in her knee and arms.tumors in both of her lungs has been detected.Dr. diagnosed 4th stage. How long will she survive? [/INST] Thanks for your question on Chat Doctor. I can understand your mother s situation and problem. Your mother is having stage 4 thyroid cancer. Lung metastasis in thyroid cancer is very rare. But when present, suggests poor prognosis. Stage 4 thyroid cancer is having life expectancy of less than 2 years. Five year survival rate is less than 30%. Chemotherapy can increase survival rate in some patients. So better to consult oncologist and start appropriate chemotherapy. </s>