RecruitingPhase 4Drug trialClinical Study of Fruquintinib Combined With Raltitrexed in the Treatment of Metastatic Colorectal CancerTo evaluate the efficacy and safety of Fruquintinib combined with Raltitrexed in the treatment of metastatic colorectal cancer that progressed or could not be tolerated after previous fluorouracil, oxaliplatin, and irinotecan based therapy