Circulating Cell-Free Tumor DNA Testing in Guiding Treatment for Patients With Advanced or Metastatic Colorectal Cancer

Inclusion Criteria: * Patients must have histologically or cytologically confirmed colorectal cancer. * Patients must have advanced or metastatic disease with no curative options. * Patients must have radiographically evaluable disease. * Patients must have had at least 2 prior therapies for mCRC (including fluorouracil \[5-FU\], oxaliplatin, irinotecan, bevacizumab; cetuximab/panitumumab \[for RAS wild type (WT) patients\]) and have either progressed on or intolerant to these agents or use of these agents is contraindicated. * Patients must be clinically eligible for either regorafenib or TAS-102 as per their treating physician. * Patients must have a negative serum pregnancy test done less than are equal to 14 days prior to randomization for women of childbearing potential only. Women of child bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry for the duration of study participation. * Patients must have ability to complete questionnaire(s) by themselves or with assistance. * Patients must have ability to provide informed written consent. * Patients must be willing to return to enrolling institution for follow-up as per study schedule. * Patients must be willing to provide blood samples for correlative studies. * Any of the following: Pregnant or nursing women, men or women of childbearing potential who are unwilling to employ adequate contraception. * Co-morbid systemic illnesse…