ALK and non-small cell lung carcinoma: At present, there is no meta-analysis of the efficacy comparison between Alectinib and Crizotinib, we combined three studies to evaluate the systemic efficacy and safety of Alectinib versus Crizotinib to provide the further reliable basis for Alectinib as the most recommended first-line medication for ALK-positive stage III or IV NSCLC.