The benefits and risks of pembrolizumab in combination with chemotherapy as first-line therapy in small-cell lung cancer: a single-arm meta-analysis of noncomparative clinical studies and randomized control trials

BACKGROUND: Although pembrolizumab has shown clinical benefit in patients with small-cell lung cancer (SCLC), its actual efficacy in combination with a conventional chemotherapy drug has not been determined. We performed this study to discern the efficacy and risk of pembrolizumab in combination with chemotherapy as first-line therapy in SCLC patients. METHODS: We systematically searched the PubMed, ScienceDirect, Cochrane Library, Scopus, Ovid MEDLINE, Embase, Web of Science, and Google Scholar databases for relevant studies. The main outcomes were overall survival (OS) and progression-free survival (PFS). RESULTS: We identified 2980 articles and included 6 studies (5 were noncomparative open-label studies and 1 was a randomized controlled trial [RCT]) involving 396 patients in our meta-analysis. The pooled median OS (mOS) was 9.6 months (95% CI, 8.0-11.2), and the pooled median PFS (mPFS) was 4.2 months (95% CI, 2.2-6.1). The 1-year overall survival rate (OSR-1y) and 6-month progression-free survival rate (PFSR-6m) were 45.1% (95% CI, 33-57.2%) and 41.6% (95% CI, 24.3-59%), respectively. The objective response rate (ORR) was 38.8% (95% CI, 11.9-65.67%), disease control rate (DCR) was 69.30% (95% CI, 51.6-87.0%), complete response (CR) was 2.20% (95% CI, 0.8-3.7%), partial response (PR) was 34.70% (95% CI, 7.8-61.5%), and stable disease (SD) was 20.90% (95% CI, 9.1-32.6%). The grade 3-4 adverse effect (AE) rate was 20.88% (95% CI, 1.22-54.85%). The most common AEs were neutropenia (90.16%), anemia (53.21%), dysphagia (41.96%), platelet count decrease (34.87%), and esophagitis (32.89%); severe AEs included neutropenia, respiratory failure, pneumonitis, acute coronary syndrome, and colitis/intestinal ischemia. CONCLUSIONS: The combination of pembrolizumab with conventional chemotherapy is an effective therapeutic schedule with acceptable and manageable efficacy and toxicity in patients with SCLC. More high-quality and well-designed RCTs with large sample sizes are warranted to further validate our findings. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12957-021-02410-3.