ERCC2 and esophageal squamous cell carcinoma: The importance of XPD to the NER pathway has prompted several case-control studies to assess the effect of XPD polymorphisms on the risk of such cancers as nasopharyngeal carcinoma [31], renal cell carcinoma [32], prostate cancer [33], esophageal squamous cell carcinoma [34], and breast cancer [35].