A very interesting paper just published in the Archives of Internal Medicine. The study followed women before and after the introduction of a breast screening programme in Norway. They were compared to a control group of women who did not take part in the screening programme, but who would have been, had the programme been started in their area. This control group were invited for a one-off screening at the end of the observation time in order to work out how many had invasive breast cancers.

When the two groups were compared, the amount of invasive breast cancers was found to be significantly higher in the group of women who had regular screening. On first glance, this may appear to be a good thing – it seems that screening picked up more invasive breast cancers. But is it? The problem is that the natural history of these “invasive breast cancers” may not be as predictable as we would like to think, in that not all may cause a life-threatening situation. The authors concluded that “it appears that some breast cancers detected by repeated mammographic screening would not persist to be detectable by a single mammogram at the end of 6 years. This raises the possibility that the natural course of some screen-detected invasive breast cancers is to spontaneously regress”.

This is but one paper in a complex field, and I wouldn’t suggest that this research alone should make women decide what to do when the invitation to breast screening comes in. However, there are already uncertanties about how beneficial breast screening is. I think this paper does emphasise that there are still a lot of unknowns when it comes to breast cancer screening. The NHS Behind the Headlines service provides a useful analysis of the news coverage of this story but concludes that “women should continue to attend screening programmes”. I think this is a bit unfair; surely the best position is to invite women to weigh up the pros and cons for themselves, as they become known. But maybe this is also unfair; most people probably don’t have the time to devote to investigating this sort of thing and they should be able to expect disinterested, fair advice from their health professionals.