Prediction of the response of colorectal cancer to systemic therapy.

Adjuvant chemotherapy with fluorouracil and folinic acid improves overall survival for resected carcinoma of the colon of Dukes' stage C by 10-12%. In metastatic disease, response rates with fluorouracil-based regimens are about 25%. Combination with newer agents such as irinotecan and oxaliplatin can improve response rates to more than 50% in selected patients. New treatments with novel molecular targets will soon be entering clinical use. Despite these improvements, many patients undergo chemotherapy for resistant cancer, thus incurring side-effects without benefit. Expression of particular genes can be tested at the protein or RNA level and can be correlated with response or resistance to particular systemic therapies. Thus, predictive-factor testing of tumour biopsy samples may allow us to select chemotherapy or immunotherapy treatments with a high likelihood of benefit for the individual patient.