Maintenance Strategy With Fluoropyrimidines (Fp) Plus Bevacizumab (Bev), Bev Alone, Or No Treatment, Following A Standard Combination Of Fp, Oxaliplatin (Ox), And Bev As First-Line Treatment For Patients With Metastatic Colorectal Cancer (Mcrc): A Phase Iii Non-Inferiority Trial (Aio Krk 0207).