Current commonly used second-line approaches for SCLC include re-induction with first-line therapy for chemosensitive disease, or single-agent topotecan. Although the efficacy of topotecan as second-line chemotherapy for SCLC has been consistently demonstrated in a number of clinical studies, the choice of irinotecan as first-line therapy prevented use of the evidence-based option such as topotecan. Topotecan and irinotecan are cytotoxic agents that inhibit same intracellular pathway, namely topoisomerase I, which is an enzyme involved in DNA replication and RNA transcription.