Prevalence of lung tumors in patients with esophageal squamous cell carcinoma and vice versa: a systematic review and meta-analysis

Purpose Recent reports suggest an increased prevalence of lung second primary tumors (LSPTs) in esophageal squamous cell carcinoma (ESCC) patients and vice versa. However, the exact prevalence of SPTs remains unclear and screening for these SPTs is currently not routinely performed in western countries. We aimed to report on the prevalence of LSPTs in patients with ESCC and esophageal second primary tumors (ESPTs) in patients with lung cancer (LC). Methods Databases were searched until 25 March 2021 for studies reporting the prevalence of LSPTs in ESCC or vice versa. Pooled prevalences with 95% confidence intervals (CI) of SPTs were calculated with inverse variance, random-effects models and Clopper-Pearson. Results Nineteen studies in ESCC patients and 20 studies in LC patients were included. The pooled prevalence of LSPTs in patients with ESCC was 1.8% (95% CI 1.4-2.3%). For ESPTs in LC patients, the pooled prevalence was 0.2% (95% CI 0.1-0.4%). The prevalence of LSPTs in ESCC patients was significantly higher in patients treated curatively compared to studies also including palliative patients (median 2.5% versus 1.3%). This difference was consistent for the ESPT prevalence in LC patients (treated curatively median 1.3% versus 0.1% for all treatments). Over 50% of the detected SPTs were squamous cell carcinomas and were diagnosed metachronously. Conclusion Patients with ESCC and LC have an increased risk of developing SPTs in the lungs and esophagus. However, the relatively low SPT prevalence rates do not justify screening in these patients. Further research should focus on risk stratification to identify subgroups of patients at highest risk of SPT development.