Effectiveness of image‐guided radiotherapy for locally advanced esophageal squamous cell carcinoma patients treated with definitive concurrent chemoradiotherapy

BACKGROUND: Image‐guided radiotherapy (IGRT) is an advanced radiotherapy technique to improve the accuracy of treatment delivery. However, a recent randomized controlled trial (RCT) for prostate cancer patients treated with radiotherapy either via IGRT or routine care (no daily IGRT) reported a statistically significant worse overall survival for those treated with IGRT. This raised the concern regarding the effectiveness of IGRT for definitive concurrent chemoradiotherapy (dCCRT) for locally advanced esophageal squamous cell carcinoma (LA‐ESqCC). METHODS: Eligible LA‐ESqCC patients diagnosed between 2011 and 2015 were identified via the Taiwan Cancer Registry. We estimated propensity scores to construct a 1:1 propensity‐score‐matched groups and balance observable potential confounders. The hazard ratio (HR) of death as well as other outcomes was compared between IGRT and non‐IGRT matched groups during the entire follow‐up period. The impact of additional covariables was considered in the sensitivity analysis. RESULTS: Our study population included 590 patients in the primary analysis. The HR for death when IGRT was compared with non‐IGRT was 0.92 (95% confidence interval 0.77–1.10, P = 0.35). There were also no significant differences for other outcomes or sensitivity analyses. CONCLUSIONS: In this updated nonrandomized study using real world data, we found that the overall survival of LA‐ESqCC patients treated with dCCRT was not statistically different between those treated with IGRT versus those without IGRT, although the hazard ratio was less than unity, ie, in favor of IGRT. The results should be interpreted with caution given the nonrandomized design and RCTs are needed to clarify our findings. KEY POINTS: Significant findings of the study: The OS of LA‐ESqCC patients treated with dCCRT was not statistically different between those treated with IGRT versus those without IGRT, although the hazard ratio was less than unity, ie, in favor of IGRT. What this study adds: In this updated nonrandomized study using real world data with additional potential confounders, our study provided a reasonable tentative evidence of lack of RCT as suggested in the literature.