Cancer treatment outcomes are influenced by a number of factors - they depend both on the severity of the condition at the time of treatment initiation and what other drugs the patient is using. One of the most recent studies on the impact of other pharmaceuticals on colorectal cancer treatment outcomes was carried out in Canada and analysed the effect of concomitant proton pump inhibitors (PPIs) on the efficacy of capecitabine in gastrointestinal cancer therapy.