Addition of Induction or Consolidation Chemotherapy in Definitive Concurrent Chemoradiotherapy Versus Concurrent Chemoradiotherapy Alone for Patients With Unresectable Esophageal Cancer: A Systematic Review and Meta-Analysis

BACKGROUND: Concurrent chemoradiotherapy (CCRT) has become the standard of care in esophageal carcinoma patients who are not surgical candidates. The efficacy of induction chemotherapy (IC) or consolidation chemotherapy (CCT) for unresectable esophageal cancer (EC) treated with CCRT is unclear. We performed a systematic review and meta-analysis of published papers to evaluate the potential benefit of IC or CCT for patients with EC. METHODS: Eligible studies of IC followed by CCRT (IC-CCRT) vs. CCRT alone or CCRT followed by CCT (CCRT-CCT) vs. CCRT alone were retrieved through extensive searches of the PubMed, Science Direct, Embase, and Cochrane Library databases from the establishment of the database to July 31, 2021. Data such as 1-, 2-, 3-, and 5-year overall survival (OS), local recurrence rate (LRR), and distant metastasis rate (DMR) were collected for meta-analysis to evaluate the efficacy of IC/CCT. RESULTS: Four studies of IC-CCRT vs. CCRT including 836 EC patients and six studies of CCRT-CCT vs. CCRT including 1,339 patients with esophageal squamous cell carcinoma (ESCC) were finally identified in our analysis. Both IC-CCRT group [hazard ratio (HR) 0.446, 95% CI 0.286–0.693; p < 0.001] and CCRT-CCT group (HR 0.542, 95% CI 0.410–0.716; p < 0.001) exhibited statistically significant improvement in 1-year OS rate compared to that of CCRT, while the 2-year OS rate of IC-CCRT (HR 0.803, 95% CI 0.589–1.095; p = 0.166) or CCRT-CCT (HR 0.783, 95% CI 0.600–1.022; p = 0.072) was similar with that of CCRT. And the 3-year OS rate between IC-CCRT and CCRT was similar (HR 1.065, 95% CI 0.789–1.439; p = 0.680). However, comparing with CCRT alone, the CCRT-CCT group had lower DMR [odds ratio (OR) 1.562, 95% CI 1.090–2.240; p = 0.015] and higher 3-year OS rate (HR 0.786, 95% CI 0.625–0.987; p = 0.039). Besides, no differences were observed between the CCRT-CCT and CCRT groups in 5-year OS rate (HR 0.923, 95% CI 0.706–1.205; p = 0.555) and LRR (OR 0.899, 95% CI 0.686–1.179; p = 0.441). CONCLUSION: The study revealed the short-time survival benefit of additional IC or CCT compared to CCRT alone for patients with unresectable EC, and CCRT followed by CCT could significantly reduce the risk of distant metastases.