Wednesday, 12 September 2007

Misleading Headlines

Listening to Radio 4's Today programme this morning they announced that the oral contraceptive pill can lower the risk of cancer in the short term but over 8-years it increases the risk of "the disease". That's right, the unitary disease that is cancer.

It often seems to be the case that these little headline gobbets of news misrepresent the real story in significant ways, even in the supposedly intelligent Today programme. Apart from an interview with one of the researchers (who made the point himself) they never actually made clear that what we are looking at here is the differential risks of various cancers (large bowel, uterine, ovarian, breast, cervical etc) - even though the BBC News story online makes this abundantly clear.

Of course no one discussed the more interesting question of differential survival rates from different cancers - and thus whether the increased or decreased risk of "the disease" means anything in terms of mortality (the original study doesn't do this either). The study is in the BMJ and shows increased risks of invasive cervical (over 2.5x) and CNS or pituitary cancers (over 5x) in OCP users of more than 97 months duration, and decreased risk of ovarian cancer (<0.5x) - resulting in an overall increased relative risk of any cancer of 1.22 (95% CI 1.07-1.39). Significant trends were found for an association between length of OCP use and increasing rates of cervical and central nervous system or pituitary cancer, and decreasing risk of uterine body and ovarian cancer.

I don't think I'll try and figure out which cancers are 'worse' right now - that's a whole can of worms.

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