Comparison of survival benefits between simultaneous integrated boost intensity-modulated radiotherapy and conventional fractionated radiotherapy for esophageal squamous cell carcinoma

Objective To investigate the survival benefits of simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) in the treatment of esophageal squamous cell carcinoma (ESCC). Methods From July 2003 to March 2014, 1 748 patients with ESCC received 3DCRT or IMRT in a single institution were enrolled in this retrospective study. Among them, 809 patients received conventional fractionated radiotherapy with the standard prescription dose and 110 patients received SIB-IMRT (SIB-IMRT group). Survival analysis was performed and propensity score matching (PSM 1vs1) was conducted to evaluate and compare the survival benefits between SIB-IMRT and conventional fractionated radiotherapy. Results The baseline characteristics significantly differed between two groups. In the SIB group, the age was significantly younger (64 years vs. 66 years, P=0.001), the percentage of patients with cervical/upper thoracic tumors was considerably higher (53.6% vs. 31.0%, P=0.000) and the proportion of N2 patients was significantly higher (21.8% vs. 13.7%, P=0.027) compared with those in the other group. According to the PSM of 1: 1, 218 patients were successfully matched. After matching, the clinical data did not significantly differ between two groups. Prior to matching, the median survival time in the standard dose and SIB-IMRT groups were 23 and 21 months (P=0.638). After matching, the median survival time in the SIB-IMRT group was 22 months, significantly longer than 18 months in the standard dose group (P=0.000). Subgroup analysis demonstrated that patients with large tumors (GTV volume>40 cm3) and middle/lower thoracic tumors obtained more survival benefits from SIB-IMRT.The median survival time of patients in the standard dose group was 14 months, significantly shorter than 21 months in the SIB-IMRT group (P=0.001). The median survival time of patients with middle/lower thoracic tumors in the SIB-IMRT group was 17 months, significantly longer than 9 months in the standard dose group (P=0.000). Multivariate analysis using Cox regression model indicated that age, tumor site and radiotherapy modality were the independent prognostic factors. The HR of SIB-IMRT was 0.551(P=0.000), which was a factor for survival benefits. Conclusions SIB-IMRT possesses potential survival benefits for ESCC compared with conventional fractionated radiotherapy. Patients with large tumors and middle/lower thoracic tumors are more prone to obtaining benefits from SIB-IMRT than their counterparts. Key words: Esophageal neoplasm/radiotherapy; Prognosis