Clinical impact of amrubicin monotherapy in patients with relapsed small cell lung cancer: a multicenter retrospective study

Background: Topoisomerase is an essential enzyme for deoxyribonucleic acid replication, and its inhibitors suppress tumor progression. Amrubicin, a topoisomerase II inhibitor, is mainly used in the second-line treatment of patients with extensive-stage small cell lung cancer (ES-SCLC). However, the impact of different types of topoisomerase inhibitors for first-line chemotherapy on the efficacy of amrubicin remains unclear. In the present study, we aimed to evaluate the efficacy of second-line amrubicin in patients with relapsed SCLC who were previously treated with platinum-based chemotherapy, including topoisomerase I and II inhibitors. Methods: This study retrospectively analyzed patients with ES-SCLC who experienced recurrence and were treated with amrubicin at 22 institutions in Japan between April 2015 and November 2020. The progression-free survival of amrubicin monotherapy was investigated using the Kaplan-Meier method. Results: A total of 320 patients were enrolled in this study, with 59 (18%) receiving platinum plus topoisomerase I inhibitor irinotecan and 261 (82%) receiving platinum plus topoisomerase II inhibitor etoposide as first-line treatment. The progression-free survival of amrubicin was significantly longer in the irinotecan group than in the etoposide group (3.2 vs. 2.5 months; P=0.034). Conclusions: These results showed that different types of topoisomerase inhibitors could affect the efficacy of amrubicin monotherapy in the second-line treatment of patients with relapsed ES-SCLC.