How long it takes for small cell lung cancer to recur after chemotherapy is different for everyone. Some patients will have tumor recurrence and progression 2-3 months after the end of chemotherapy, and recurrence and progression within 6 months will need to change the chemotherapy regimen or combine with local radiotherapy, and at present, targeting drugs such as oral apatinib or amiloride hydrochloride can also be considered for treatment. In some cases, PD-1/PD-L1 immunosuppressant therapy can also be considered. In some cases, small cell lung cancer may recur and progress after 6 months of chemotherapy, the original chemotherapy regimen can be considered to continue to be used, and if there is no effect after two cycles of review, it can be considered to change to the above treatment regimen.