We recenty held an information session on breast cancer screening. The aim was to provide an overview of the current evidence on population breast cancer screening and overdiagnosis.
Prof Dallas English posed the question 'Does mamographic screening save lives'? He sited research in randomised control trials, case control, cohort studies and time trends. Dallas then asked 'Are women treated for cancer unncessarily'? and explained overdaignosis and overtreatment giving examples of studies and estimates from screening programs.
Dallas conculded that there is increasing recognition that screening programs need to inform women better about the benefits and harms of breast screening. You can watch the presentations on YouTube below.
Dr Nicola Bruce, Cancer Voices Victoria and member of our VCOG Breast Cancer Committee gave an account of the evening, see below.
Prof Dallas English
- Professor of Epidemology and Biostatistics, and Director of Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, The University of Melbourne.
- Member of BreastScreen Australia Evaluation Advisory Committee, and Board Member of BreasScreen Victoria
Download Dallas English's presentation on sceening for breast cancer - what is all the fuss about? (367kb)
Summary by Dr Nicola Bruce, Cancer Voices Victoria
On Monday 13th of August I attended a VCOG breast cancer screening forum entitled Breast Cancer Screening: An overview of the spectrum of evidence, presented by Professor Dallas English.
I have observed for many years now intermittent press coverage questioning the efficacy of breast screening. The first time I read about this was a report that showed how women experienced unnecessary ‘harms' with breast screening. The journal article (1) referred to the unnecessary procedures women would go through when being investigated for a suspicious screening result but which was eventually found to be negative.
For a woman who has experienced a breast cancer diagnosis I was amazed that these very necessary investigations were described as harmful. Recently, there have been further news articles about over diagnosis of breast cancers that would, if left untreated, not develop into life threatening cancers that spread. So I was particularly interested to hear Professor Dallas English provide an overview of this contradictory evidence.
Professor English described how RCT (randomised control trial) studies conducted between the 1960s and 1980s provided the evidence leading to the establishment of breast screening around the world. RCTs provided the best quality of research in the hierarchy of evidence for the times and indicated about a 20% benefit (2) (with high participation in screening). Because it would not be ethically valid to conduct similar research nowadays, current planning for breast screening relies on lesser valid (but still relevant) research in the hierarchy.
But, what about the studies that question the efficacy of breast screening? Professor English suggested that many of the trials that were critical to breast screening relied on insufficient data and/or reported on inconsistent areas of the data collection. He highlighted that study results are dependent on which figures are accounted for and, if the figures are incomplete, results can be skewed.
There is currently information about over-diagnosis provided by organisations such as BreastScreen Australia and Cancer Council Australia, however there is a lack of balance in the key messages Australia women receive via the media.
Perhaps the challenge for health services and population health academics is to work with the media to counter the messages that can cause unnecessary panic. For me, such unbalanced information is where the harm exists. I further propose that we need to find out what women see as harms and come to some understanding as to how women understand them.
A key message I took from Professor English is that over diagnosis does exist. However, no current way of precisely distinguishing potentially fatal cancers from non-fatal exists and until a way is identified, it is necessary to offer treatment to all women diagnosed with breast cancer through breast cancer screening. It appears more research is required in identifying harmful cancers as well as the impact of over-diagnosis
Olsen O, GØtzsche PC. Cochrane review on screening for breast cancer with mammography. Lancet 2001; 358: 1340-1342.
2.Screening for Breast Cancer
(2002). July 2010. U.S. Preventive Services Task Force.