CXCR4 and colorectal cancer: While these clinical trials are evaluating these agents in patients with advanced cancer, the ideal setting to demonstrate the efficacy of CXCR4 inhibitors will be as metastasis-preventing agents in the adjuvant and neoadjuvant setting with tumors such as colorectal cancer [47] and in the prevention of first recurrence after radiotherapy in glioblastoma [8], [18], [48].