Second-line treatment options are limited for patients with small-cell lung cancer (SCLC). We conducted a PRISMA-standard systematic literature review to evaluate the treatment landscape for patients with relapsed SCLC (PROSPERO number: CRD42022299759). Systematic searches of MEDLINE, Embase, and Cochrane Library were performed (October 2022) to identify publications (prior 5 years) from prospective studies of therapies for relapsed SCLC. Publications were screened against predetermined eligibility criteria; data were extracted to standardized fields. Publication quality was assessed using GRADE. The data were analyzed descriptively, grouped by drug class. Overall, 77 publications involving 6349 patients were included. Studies of tyrosine kinase inhibitors (TKIs) with established cancer indications accounted for 24 publications; topoisomerase I inhibitors for 15; checkpoint inhibitors (CPIs) for 11, and alkylating agents for 9 publications. The remaining 18 publications featured chemotherapies, small-molecule inhibitors, investigational TKIs and monoclonal antibodies, and a cancer vaccine. According to GRADE assessment, 69% of the publications reported low-/very-low-quality evidence; quality limitations included lack of randomization and small sample sizes. Only 6 publications/6 trials reported phase 3 data; 5 publications/2 trials reported phase 2/3 results. Overall, the clinical potential of alkylating agents and CPIs remained unclear; investigations of combination approaches and biomarker-directed usage are warranted. Phase 2 data from TKI trials were consistently promising; no phase 3 data were available. Phase 2 data for a liposomal formulation of irinotecan were promising. We confirmed an absence of promising investigational drug/regimens in late-stage development; thus, relapsed SCLC remains an area of high unmet need.
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