Effect of locoregional risk factors on long-term prognosis of patients with N0 stage esophageal cancer receiving intensity-modulated radiotherapy

Objective To evaluate the effect of locoregional risk factors of esophageal cancer on the recurrence of gross tumor volume (GTV) in patients with N0 esophageal squamous cell carcinoma after radical intensity-modulated radiotherapy (IMRT) and to evaluate its effect on the 10-year survival of patients. Methods Clinical data of 374 patients with clinical N0 esophageal squamous cell carcinoma who underwent radical IMRT in the Fourth Hospital of Hebei Medical University from 2005 to 2010 were retrospectively analyzed. Involved-field irradiation was performed in 284 patients and selective lymph node irradiation was given in 90 patients. Concurrent radiochemotherapy was conducted in 69l patients and sequential radiochemotherapy was performed in 38 patients. The survival analysis was carried out by Kaplan-Meier method. The prognosis analysis was performed by multivariate Cox’s regression model. Results A total of 143 patients (38.2%) had recurrence in GTV. The maximum transverse diameter (GTV-D), GTV volume (GTV-V) and GTV volume/length (GTV-V/L) of GTV patients were significantly longer than those without recurrence in GTV (P=0.008, 0.043, 0.001). ROC curve analysis showed that the optimal diagnostic thresholds for GTV-D, GTV-L, GTV-V and GTV-V/L for GTV recurrence were 3.5 cm, 5.5 cm, 24.0 cm3 and 4.6 cm2, respectively (P=0.000, 0.003, 0.000 and 0.000), and the ratio of recurrence within GTV in the patient group was significantly greater than that in the smaller group (P=0.000, 0.002, 0.001 and 0.000). GTV-L and GTV-V/L were the independent risk factors of recurrence in GTV (P=0.021 and 0.009). The 3-, 5-and 10-year survival rates of all patients in the whole group were 42.9%, 23.2% and 7.9%, respectively. Multivariate analysis demonstrated that age, T stage, concurrent radiochemotherapy, GTV-D and GTV-V/L were the independent risk factors of survival (P=0.027, 0.000, 0.018, 0.009 and 0.034). The main cause of death in patients with a survival time of more than 5 years was still associated with cancer. Conclusions The locoregional risk factors of esophageal cancer exert significant effect on the recurrence of GTV in patients with N0 esophageal squamous cell carcinoma undergoing radical radiochemotherapy, which can be utilized as the predicting markers. Both GTV-D and GTV-V/L are significantly correlated the 10-year survival of patients. Key words: Esophageal neoplasm/radiochemotherapy; Recurrence of primary tumor bed; Prognosis