Efficacy and Safety of Amrubicin Monotherapy After Atezolizumab Plus Carboplatin and Etoposide in Patients with Relapsed Small-cell Lung Cancer

This study examined the activity and safety of amrubicin monotherapy among relapsed small-cell lung cancer (SCLC) patients who had previously been treated with atezolizumab plus carboplatin and etoposide (AteCE). This retrospective study evaluated patients with relapsed SCLC who were treated with previously AteCE combination therapy followed by amrubicin monotherapy between August 2019 and May 2021. Clinical efficacy and toxicity were analyzed. Overall, 40 patients were included: 12 and 28 patients had sensitive and refractory relapse, respectively. The response rate was 32.5% (25.0% in the sensitive group and 35.7% in the refractory group). The median progression-free survival (PFS) and overall survival (OS) from the first amrubicin treatment was 3.4 months (95% CI: 1.9-4.9 months) and 9.9 months (95% CI: 4.5-11.5 months), respectively. There was no significant between-group difference in median PFS (3.6 months vs. 3.2 months, p = 0.42) or median OS (11.2 months vs. 7.3 months, p = 0.78). Grade ≥ 3 hematological adverse events occurred as follows: decreased white blood cells in 52.5% of patients; decreased neutrophil count in 57.5%; and febrile neutropenia in 10.0%. Grade 3 pneumonitis was observed in one patient. There were no treatment-related deaths. Amrubicin is feasible and effective for relapsed SCLC patients previously treated with AteCE therapy. Although immune checkpoint inhibitor treatment (ICI) does not improve the effect of amrubicin, the toxicity is not increased, suggesting that amrubicin remains effective even after ICI administration. Thus, amrubicin after AteCE could be the preferred standard chemotherapeutic choice in patients with relapsed SCLC.