Clinical efficacy of amrubicin in patients with small cell lung cancer relapse after first-line treatment including immune checkpoint inhibitors: A retrospective multicenter study (TOPGAN 2021-01)

Background: The therapeutic efficacy of cytotoxic anticancer drugs has been reported to be enhanced after immune checkpoint inhibitors (ICI) in non–small cell lung cancer; however, it is unclear whether the same is applicable for small cell lung cancer (SCLC). We evaluated the efficacy of second-line amrubicin (AMR) following first-line platinum-based chemotherapy and ICI combination therapy (chemo-ICI) in SCLC. Patients and Methods: We retrospectively enrolled consecutive patients with SCLC treated with AMR as a second-line following chemo-ICI as first-line between July 2019 and April 2021 from 16 institutions throughout Japan. We investigated the therapeutic effectiveness, safety, and efficacy-enhancing variables of AMR. Results: Overall, 89 patients treated with AMR after first-line chemo-ICI were analyzed. The overall response rate (ORR) was 29.2% (95% confidence intervals [CI], 20.1–39.8) and median PFS (m PFS) was 2.99 months (95% CI, 2.27–3.65). Patients who relapsed more than 90 days after receiving first-line platinum combination therapy (sensitive relapse) exhibited greater ORR (58.3% vs. 24.7%, p = 0.035) and m PFS (5.03 vs. 2.56 months, p = 0.019) than patients who relapsed in <90 days (refractory relapse). Grade 3 or higher adverse events were mainly hematological toxicity. Conclusions: Our study suggested that the therapeutic effect of AMR was not enhanced after ICI on SCLC. However, AMR may be effective in cases of sensitive relapse after chemo-ICI. There was no increase in severe toxicity associated with AMR after ICI.