Breast cancer: to
screen or not to screen?
Reported December 01, 2008
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.
