Health: Paracetamol could stave off cancer

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Painkillers bought over the counter can prevent cancer. Scientists have shown that aspirin and similar anti-inflammatory drugs used in the treatment of arthritis reduce the risk of bowel cancer. The mechanism is unclear but it is thought that the drugs may stop the production of chemicals in the intestine that are necessary to allow the cancer to grow.

Now scientists at the Brigham and Women's hospital, Boston, Massachusetts, have tested the effect of over-the-counter analgesics on ovarian cancer. They speculated that whatever mechanism was at work with aspirin in bowel cancer might also apply to other cancers, but they included questions about the use of paracetamol and ibuprofen in their study.

To their surprise, they found a positive link with paracetamol but no significant association with either aspirin or ibuprofen use. Women who took paracetamol regularly were half as likely to develop ovarian cancer as those who did not.

The numbers in the study, published in the Lancet medical journal, were small and the researchers stress that their findings are preliminary. They say the study must be replicated and the protective mechanism explained before any public health advice can be given.

A total of 563 women with ovarian cancer were compared with 523 from the general population and the researchers found that 26 of the cases (4.6 per cent) used paracetamol compared with 46 of the controls (8.8 per cent). The women with the lowest risk took paracetamol daily or had used it for more than 10 years.

The researchers say that paracetamol cannot work against cancer in the same way as aspirin. However, there is evidence from studies on rats that paracetamol suppresses the activity of the ovaries, which might account for its cancer-preventing effect.

Paracetamol is metabolised in the liver in a process that may require the chemical glutathione. This is also required for the release of follicle- stimulating hormone (FSH) which is essential to achieve ovulation. The researchers suggest that if glutathione is taken up in metabolising paracetamol, it could result in depleted levels of FSH.

They say: "Until the validity of and mechanism for a possible association between paracetamol and ovarian cancer protection are better defined, this association cannot yet be regarded as one which would prompt a public health recommendation."