The TTP data from this research demonstrate a probable role of DNA repair in resistance to treatment, thus highlighting the importance of further investigating specific DNA repair gene activity as potential biomarkers, although the largest biomarker study in metastatic CRC conducted to date did not show any predictive value of the two DNA repair genes studied (XRCC1 and MLH1) with irinotecan outcome 31. The gene discussed is XRCC1; the disease is colorectal carcinoma.