Metastatic colorectal cancer

Abstract

Despite advances in screening procedures and the use of adjuvant therapy, approximately 50% of patients with colorectal cancer eventually will develop metastatic disease. Long-term disease-free survival can be achieved in 25% to 40% of selected patients who undergo resection of liver or lung metastases. For all other patients, treatment is palliative. For decades, 5-fluorouracil was the only available drug for colorectal cancer; hence, numerous trials were performed that used various administration schedules and modulating agents to improve therapeutic efficacy. The addition of leucovorin to 5-FU improves response but not survival. Infusion schedules alter the toxicity profile but have a negligible impact on survival. Irinotecan was the first new drug to demonstrate activity in colorectal cancer. It was used initially in the second-line setting, where it was shown to improve quality of life and survival over best supportive care or infusional 5-FU. Recently, irinotecan has been incorporated into the front-line treatment of metastatic colorectal cancer in combination with 5-FU and leucovorin; this combination improves survival by approximately 3 months. Careful patient selection and adherence to strict dose adjustments are essential to prevent significant toxicity when patients are treated on this regimen. The oral fluoropyrimidine capecitabine recently has been approved for the front-line treatment of patients with colorectal cancer who are not appropriate candidates for combination therapy. Oxaliplatin, a novel DACH (diaminocyclohexane) platinum with definite activity in colorectal cancer, is approved for this disease in Europe and is undergoing phase III clinical trials in the United States. Other drugs with potential activity in colorectal cancer include raltitrexed, pemetrexed disodium, and the epothilone analog BMS-247550 (Bristol-Myers Squibb, New York, NY). Novel cytostatics with promising activity in colorectal cancer are being evaluated in clinical trials, including epidermal growth factor receptor inhibitors, such as IMC-C225 (Imclone Systems, New York, NY) and ZD1839 (AstraZeneca, London, UK), angiogenesis inhibitors such as bevacizumab and SU5416 (Sugen, San Francisco, CA), and vaccines such as CEAVac (Titan Pharmaceuticals, San Francisco, CA). For those patients whose disease is localized to the liver, there also is an emerging role for local therapies, including cryosurgery, radiofrequency ablation, and hepatic artery infusional chemotherapy, and resection. The emergence of these new drugs and new interventional modalities has allowed physicians who treat colorectal cancer to move beyond 5-FU.