Prior Cancer and Survival in Patients With Esophageal Squamous Cell Carcinoma.

Importance: Esophageal squamous cell carcinoma (ESCC) is highly prevalent in Asian populations and carries a poor prognosis. With growing numbers of cancer survivors, the prognostic impact of prior cancer in ESCC remains unclear. Most existing data are derived from Western cohorts dominated by adenocarcinoma, limiting generalizability to Asian populations. Objective: To evaluate whether prior cancer is associated with overall survival (OS) and esophageal cancer-specific mortality (ECSM) in a nationwide Korean ESCC cohort. Design, Setting, and Participants: A retrospective cohort study of patients with newly diagnosed ESCC across 19 tertiary hospitals in Korea from 2005 to 2017 was conducted. Follow-up was completed in 2017. Data were reanalyzed in August 2025. Exclusion criteria were nonsquamous histology (including adenocarcinoma), diagnosis of esophageal cancer within 6 months of a prior cancer, multiple prior cancers, and hematologic cancers. Exposures: History of cancer before the diagnosis of ESCC, classified by cancer type and latency (≤5 years vs >5 years). Main Outcomes and Measures: The primary outcome was OS, and the secondary outcome was esophageal cancer-specific mortality (ECSM). Hazard ratios (HRs) and cause-specific hazard ratios (CSHRs) were estimated after adjustment for clinicopathologic and treatment variables. Propensity score-adjusted Cox regression and competing risk regression models were used. Subgroup analyses were conducted by prior cancer type and latency period. Results: Of the 5557 patients (mean [SD] age, 64.7 [8.9] years; 5168 [93.0%] male), 368 (6.6%) had a prior cancer and were older and more often diagnosed at an earlier stage than those without prior cancer. Patients with a prior cancer had significantly poorer outcomes, with a median OS of 3.58 (95% CI, 2.50-4.92) vs 4.25 (95% CI, 3.83-4.58) years and a 3-year ECSM of 8.35% (95% CI, 4.42%-12.29%) vs 4.98% (95% CI, 4.17%-5.78%) compared with those without a prior cancer. Prior cancer was independently associated with worse OS (HR, 1.25; 95% CI, 1.07-1.47) and ECSM (CSHR, 1.89; 95% CI, 1.09-3.29). Among prior cancer types, patients with a history of stomach, head and neck, or lung cancer demonstrated poorer OS (HR, 1.63; 95% CI, 1.24-2.15; P < .001). A latency of 5 or more years was also associated with reduced OS (HR, 1.27; 95% CI, 1.03-1.57; P = .02). Conclusions and Relevance: In this nationwide Korean cohort study, prior cancer was an independent adverse prognostic factor in ESCC, with stomach, head and neck, and lung cancers associated with the poorest outcomes.