To examine whether the following protocol and regimen is appropriate for the phase III clinical trial on extensive-stage disease (ED) small cell lung cancer: set test groups of cisplatin + irinotecan + Krestin therapy as first-line treatment and chemotherapy (radiotherapy or radiotherapy + chemotherapy also allowed) combined with Krestin as second-line treatment after exacerbation, evaluate the efficacy and safety of treatment in a small number of cases, and compare with historical control or community control.