Combined assessment of clinical and pathological prognostic factors for deciding treatment strategies for esophageal squamous cell carcinoma invading into the muscularis mucosa or submucosa after endoscopic submucosal dissection

Objectives: We aimed to clarify the prognostic factors for patients with esophageal squamous cell carcinoma (ESCC) invading into the muscularis mucosa (pT1a-MM) or submucosa (pT1b-SM) after endoscopic submucosal dissection (ESD). Methods: This retrospective study enrolled such patients at 21 institutions in Japan between 2006 and 2017. We evaluated 15 factors, including pathological risk categories for ESCC-specific mortality, six non-cancer-related indices, and treatment strategies. Results: In the analysis of 593 patients, the 5-year overall and disease-specific survival rates were 83.0% and 97.6%, respectively. In a multivariate Cox analysis, male sex (hazard ratio [HR] 3.56), Charlson comorbidity index (CCI) ≥3 (HR 2.53), ages of 75–79 (HR 1.61) and ≥80 years (HR 2.04), prognostic nutrition index (PNI) <45 (HR 1.69), and pathological intermediate-risk (HR 1.63) and high-risk (HR 1.89) were prognostic factors. Subsequently, we developed a clinical risk classification for non-ESCC-related mortality based on the number of prognostic factors (age ≥75 years, male sex, CCI ≥3, PNI <45): low-risk, 0; intermediate-risk, 1–2; and high-risk, 3–4. The 5-year non-ESCC-related mortality rates for patients without additional treatment were 0.0%, 10.2%, and 45.8% in the low-, intermediate-, and high-risk groups, respectively. Meanwhile, the 5-year ESCC-specific mortality rates for the pathological low-, intermediate-, and high-risk groups were 0.3%, 5.3%, and 18.2%, respectively. Conclusions: We clarified prognostic factors for patients with pT1a-MM/pT1b-SM ESCC after ESD. The combined assessment of non-ESCC- and ESCC-related mortalities by the two risk classifications might help clinicians in deciding treatment strategies for such patients.