Patients with colorectal tumours expressing the wild-type KRAS gene show significantly increased progression free survival with panitumumab (Vectibix), a monoclonal antibody targeting EGFR, while those with mutations in KRAS do not, according to data from a phase 3 trial reported at the 2008 Gastrointestinal Cancers Symposium this week (25-27 January, Orlando, Florida).

The study assessed KRAS status – a gene coding for a protein involved in signalling cell division – in tumour samples from 427 patients with metastatic colorectal cancer taking part in a phase 3 trial in which they were randomised to panitumumab (6.0mg/kg every two weeks) plus best supportive care or best supportive care alone. Results reported at the meeting showed that 43% of these patients had KRAS mutations.

Patients with tumours expressing wild-type KRAS showed a 55% increase in progression free survival when treated with panitumumab compared to those given best supportive care without the antibody (hazard ratio 0.45; 95% confidence interval 0.34-0.59). In contrast, those with mutant KRAS showed no response (HR 0.99; 95% CI, 0.73-1.36) (p

[2008 Gastrointestinal Cancers Symposium. Abstract 278]

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Written by – Susan Mayor PhD, medical journalist, London, UK
susanmayor@mac.com