This clinical trial aims to see whether the addition of Omegaven to EOX chemotherapy, the most widely used regimen for patients with advanced oesophago-gastric cancer, will make this drug regimen more effective at killing oesophago-gastric cancer cells, such that disease progression is delayed. Forty-five patients who have been diagnosed with advanced oesophago-gastric cancer will be recruited over a two year period to receive standard chemotherapy and omega-3 fish oil supplementation. The results in these 45 patients will be compared to a matched historical control group of patients who have received identical chemotherapy. If results suggest that the combination of EOX and Omegaven is sufficiently effective, tolerable and feasible then it will be the intention of the trial team to take the combination forward to treat patients with advanced oesophago-gastric cancer in a randomised study.