Statins could cut the risk of dying from cancer by up to 55%, according to research.
A 15-year study of almost 150,000 people found that those taking the cholesterol-lowering drugs were more likely to survive the illness.
Experts at the world's biggest cancer conference in Chicago said they were "very excited" by the findings.
The cheap medication, which costs just 10p a day per patient, is being taken by up to eight million Britons.
For common cancers such as breast, prostate, bowel and ovarian, researchers found the death rates among those taking the drugs were at least 40% lower.
The largest difference was a 55% reduction for those suffering bone cancer.
When all cancers were taken into account, patients on the medicine were 20% less likely to die.
The research, conducted at Stanford University School of Medicine and presented at the American Society for Clinical Oncology's annual meeting, involved 146,000 American women aged 50 to 79.
Although they may not prevent cancer, experts believe they could save thousands of lives by slowing the spread of the disease.
A second study carried out at Rutgers Cancer Institute of New Jersey analysed death rates of 20,000 men with prostate cancer.
It suggested that statins were more effective than chemotherapy, experts said.
Doctors said it was not clear why they had such an effect, although cholesterol - which the drugs target - helps spread cancer.
Heart disease experts believe statins are already saving around 7,000 lives a year in the UK by tackling potential heart attacks and strokes.