Abstract
INTRODUCTION: Extensive-stage small-cell lung cancer (ED-SCLC) has a poor prognosis. There are few case reports on the therapeutic effect of pembrolizumab in advanced SCLC with high tumor mutation burden (TMB-high). CASE PRESENTATION: A 65-year-old woman was diagnosed with ED-SCLC. The initial treatment regimen included carboplatin, etoposide, and durvalumab. Following the administration of durvalumab, etoposide was discontinued due to an anaphylactic reaction immediately after its initiation. The patient was unable to continue the same regimen and was switched to cisplatin and irinotecan therapy. A FoundationOne panel test was submitted at the same time, and TMB-high was detected. After four courses of cisplatin and irinotecan therapy, pembrolizumab was introduced, and a complete response (CR) was maintained for 18 months. CONCLUSION: We report a rare case of a long-term response to pembrolizumab in ED-SCLC with TMB-high, highlighting the potential for targeted immunotherapy in such cases.