Thursday, 26 June 2014 12:15pm
New Zealand should re-consider the age at which its breast cancer screening programme starts in light of growing questions about the balance of benefits and harms for women under 50, public health experts from the University of Otago Wellington say.
In two new posts on the Public Health Expert blog, the researchers examine the possibility that the balance of benefits and harms of breast cancer screening is much less favourable than previously thought due to over-detection of cancers and other issues.
Advances in breast cancer treatment since randomised control trials (RCTs) of screening in the 1970s and early 80s have been substantial, and consequently survival and mortality have improved considerably, they write.
The trials on which the mortality benefit is estimated from are increasingly old and many have flaws in them. However the degree to which the flaws invalidate the results is a source of disagreement among experts, they say.
“There is the possibility that improved treatments in the decades since the RCTS were conducted have altered the absolute benefit of screening - as mortality has reduced due to better treatment the importance of early diagnosis through screening may have lessened.”
The extent of over diagnosis - the key harm of breast cancer screening - is hotly contested, they say.
“It is not disputed that there is over diagnosis and over treatment, but the extent of and best way to measure over diagnosis are not clear.”
They write that screening in women under 50 is not recommended by any of the independent bodies who have reviewed the evidence and no screening programmes in the UK, Canada or Australia start at under 50.
“The balance of benefits and harms in this age group is not favourable. In New Zealand we need to stop screening women under 50 and start being more honest about the lack of clarity about the evidence for screening in older women.”
The blog posts are written by Dr Caroline Shaw and Associate Professor Diana Sarfati.
We need to talk about breast cancer screening part 1
We need to talk about breast cancer screening part 2
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