Aspirin may halt cancer spread Aspirin, the most versatile drug in the pharmacy, which is already known to prevent cancer, may also be an effective treatment for halting the disease once it has started. An analysis of five large trials of people who took a daily low dose aspirin showed that among those who developed cancer it reduced its spread to distant organs by 40 to 50 per cent. The spread of cancer, or "metastasis," is what most commonly kills patients after the disease has been initially diagnosed and treated. The study is one of three published in The Lancet and Lancet Oncology which shows that taking aspirin for as little as two or three years can have a beneficial effect against cancer. Study leader Professor Peter Rothwell of the University of Oxford said: "It seems likely aspirin will be of benefit when started after cancer is diagnosed."