Oxaliplatin is a cytotoxic agent which, like other platinum compounds, acts primarily by causing inter- and intra-strand cross-links in DNA, thereby inhibiting DNA synthesis. Oxaliplatin has a bulky carrier ligand which is thought to enhance cytotoxicity and abolish cross-resistance between oxaliplatin and other platinum compounds. Phase II and III clinical trials have found oxaliplatin combined with fluorouracil/calcium folinate (leucovorin/folinic acid) to be an effective first- and second-line treatment for patients with metastatic colorectal cancer. First-line triple therapy with oxaliplatin and fluorouracil/calcium folinate achieved significantly higher response rates than fluorouracil/calcium folinate alone in 2 phase III studies (objective response rates 59 vs 23% and 50.7 vs 22.3%). In addition, median progression-free survival was longer with triple therapy in both studies (8.9 vs 5.2 and 8.75 vs 6.0 months). However, there was no significant difference in median duration of survival between treatment groups, although this may be a consequence of the subsequent use of oxaliplatin and/or surgery in patients who relapsed during therapy with fluorouracil/calcium folinate alone. About 30 to 45% of patients (whose disease progressed during or after fluorouracil-based therapy) responded to second-line combination therapy with oxaliplatin and fluorouracil/calcium folinate. Median progression-free survival ranged from 7 to 10 months and the median duration of survival from 10 to 17 months. Objective responses were achieved in 20 and 24% of patients in 2 small trials of first-line oxaliplatin monotherapy and in about 10% of patients given the drug as a second-line option. Peripheral sensory neuropathy is the dose-limiting toxicity associated with oxaliplatin. Severe neurotoxicity has been estimated to occur in 10% of patients after 6 treatment cycles and in 50% after 9 cycles of an oxaliplatin dosage of 130 mg/m2 once every 3 weeks. It is cumulative, but reversible on discontinuation of therapy. Nausea, vomiting and diarrhoea are common, but are usually mild to moderate. Myelosuppression is also observed, but is usually mild.
Conclusion: oxaliplatin is a promising treatment option for patients with metastatic colorectal cancer. It appears to be particularly advantageous (in terms of response rate and duration of progression-free survival) when used in combination with fluorouracil/calcium folinate as both a first- and second-line option, although preliminary studies have failed to show any survival advantage over fluorouracil/calcium folinate alone. Promising results have been found in studies of the drug as monotherapy, and oxaliplatin may also prove useful in the neoadjuvant setting in patients with unresectable liver metastases; however, data are limited at present.