Multiple Factors for Determination of Who Should Receive Rechallenge Treatment in Metastatic Colorectal Cancer

Colorectal cancer (CRC) is the third most common neoplasm in the world and in Turkey and the fourth most common cause of death (Haggar et al., 2009; Karaca et al., 2011). Further their incidence has increased in recent years (Jemal et al., 2010). Approximately 50% of patients with CRC present, at diagnosis, distant metastases. Since the introduction of drugs like oxaliplatin and irinotecan, the combination of these drugs with 5-Fluorouracil (5-FU) and leucovorine (LV) is considered standard chemotherapy for advanced colorectal cancers (Fuchs et al., 2007). The combination of chemotherapy with targeted biological agents such as antiepidermal growth factor receptor (anti-EGFR) and antivascular endothelial growth factor (anti-VEGF) monoclonal antibodies has increased the median OS (Hurwitz et al., 2004; Van Cutsem et al., 2009;