Risk factors for esophageal fistula in thoracic esophageal squamous cell carcinoma invading adjacent organs treated with definitive chemoradiotherapy: a monocentric case-control study

Background Standard treatment for unresectable esophageal squamous cell carcinoma (ESCC) without distant metastasis is definitive chemoradiotherapy (dCRT), in which the incidence of esophageal fistula (EF) is reported to be 10–12%. An ad hoc analysis of JCOG0303, a phase II/III trial of dCRT for patients with unresectable ESCC (including non-T4b), suggested that esophageal stenosis is a risk factor for EF. However, risk factors for EF in patients limited to T4b ESCC treated with dCRT have yet to be clarified. The aim of this study was to investigate risk factors for EF in T4b thoracic ESCC treated with dCRT. Methods We retrospectively analyzed the data of consecutive T4b thoracic ESCC patients who were treated with dCRT (cisplatin and fluorouracil) at Shizuoka Cancer Center between April 2004 and September 2015. Results Excluding 8 patients with esophageal fistula clearly attributable to other iatrogenic interventions, the data of 116 patients who met the inclusion criteria were analyzed. Esophageal fistula was observed in 28 patients (24%). Although the fistula was closed in 5 patients, overall survival was significantly shorter in patients who experienced esophageal fistula (8.0 vs. 26.8 months; p < 0.0001). Among four potential variables extracted in univariate analysis, namely, total circumferential lesion, elevated CRP level, elevated white blood cell count, and anemia, the first two were revealed as risk factors for esophageal fistula in multivariate analysis. Conclusions This study demonstrated that total circumferential lesion and CRP ≥1.00 mg/dL are risk factors for esophageal fistula in T4b thoracic ESCC treated with dCRT. Trial registration This study was retrospectively registered.