BACKGROUND: Capecitabine plus oxaliplatin (CAPOX) is an established treatment option in colorectal cancer, but can be associated with severe toxicities. METHODS: Following reporting of severe diarrhoea and dehydration with capecitabine 2000 mg m(-2) per day plus oxaliplatin every 3 weeks (CAPOX 2000) in 2006, we instituted a policy change to reduce capecitabine dose to 1700 mg m(-2) per day (CAPOX 1700). We undertook a retrospective analysis comparing toxicities encountered before and after this dose change. RESULTS: Of the 400 patients treated, no significant differences were seen between the CAPOX 2000 and CAPOX 1700 in grades 3 and 4 diarrhoea (21% vs 19%; P=0.80), stomatitis (0% vs 1%; P=0.50) or grades 2-4 hand foot syndrome (16% vs 11%; P=0.18). Grades 3 and 4 neutropenia (9.5% vs 3.5%; P=0.03) and all grades hyperbilirubinaemia (60% vs 40%; P<0.0001) were significantly reduced with CAPOX 1700. Rates of hospitalisation due to toxicities were not different between two groups (13% vs 11%; P=0.53). CONCLUSIONS: No clinically or statistically significant differences in gastrointestinal toxicities or hospitalisation rate were seen after reducing our routine capecitabine dose from CAPOX 2000 to CAPOX 1700.We acknowledge National Health Service funding to the National Institute for Health Research Biomedical Research Centre
