OBJECTIVES: To calculate incremental life years gained, ‘number needed to treat’- NNT and extra patients ‘cured’ (at 10 years), of previously unresectable liver only metastases when treating based upon KRAS status in the UK NHS. METHODS: The licence of cetuximab includes treatment of mCRC in combination with standard chemotherapy in patients with wildtype KRAS and EGFR expressing tumours. NICE (TA176) and SMC (543/09) have both recommended cetuximab plus FOLFIRI/FOLFOX for first line treatment of mCRC for patients with unresectable liver only metastases to enable potentially curative hepatic resection after treatment. A model was built in Excel to estimate the difference in survival and to calculate the incremental life years gained when treatment is selected based upon KRAS status and the addition of cetuximab to current standard of care. The potential benefit from curative-intent liver surgery was estimated using resection rates from CELIM and Tournigand et al for cetuximab/chemotherapy and chemotherapy arms respectively. The long‑term benefits of surgery were estimated from Adam et al for proportion cured and median survival time. Survival with chemotherapy was estimated from Tournigand et al. Cure rates and resection rates were varied within plausible ranges from the data. RESULTS: The addition of cetuximab to FOLFIRI/FOLFOX in KRAS wild type patients resulted in up to an extra 384 patients being eligible for liver surgery of whom an extra 88 may be ‘cured’ compared to treatment with chemotherapy alone. The increase in life years saved in the UK population is expected to be 1998 when compared to chemotherapy alone. The NNT for liver surgery and ‘cure’ respectively is 8 and 35. CONCLUSIONS: The positive guidance from NICE and SMC may save up to 88 lives p.a. and lead to an overall increase in the number of life years gained in this previously incurable population of nearly 2000.