Gene testing could improve screening programme in future
Calculating individual genetic cancer risk and taking age into account could mean fewer women would need to be screened for breast cancer, according to research published in the British Journal of Cancer1, today (Wednesday).
Based on work funded by Cancer Research UK and the European Community (COGS project), researchers say this new screening concept would still detect the same number of cancers but could also potentially reduce some of the risks associated with screening – such as false positives and subsequent anxiety – as well as saving the NHS money.
The researchers used a statistical model to compare a hypothetical age based screening programme and the number of cancers potentially detected with how many cancers would be detected if people were invited to screening based on their genetic risk of cancer as well as their age.
In England almost 31,000 cases of breast cancer are diagnosed in women aged 35 to 79. Screening all women between 47 and 79 – in a hypothetical age based screening programme – means 65 per cent of women aged 35 to 79 would be screened. And, if all women went for screening and the test was 100 per cent perfect, 85 per cent of cancers diagnosed in the 35 to 79 age group would potentially be detected.
But by using a genetic test to identify women at a higher risk of breast cancer the researchers found that the number of women screened could be reduced without reducing the number of cancers detected by screening2.
In theory, it could mean that fewer women would be screened and has the potential to reduce some of the risks linked with screening such as over diagnosis and overtreatment3.
Lead author Dr Nora Pashayan of the PHG Foundation and Cancer Research UK training Fellow, said: “This is an alternative approach to the existing screening programme and might even have the potential to reduce over-diagnosis, and in turn, lower costs.
“For our model to be used women would need to have a genetic test before the age of 35. This would be a simple blood test to identify genetic risk and, depending on the results, the age at which they should be invited for screening could be calculated. For some women this would be when they’re 35, for others not until they’re in their 50s or 60s or even later.
“This approach means that screening women at high risk of the disease when they are younger will pick up some cancers earlier. These cancers tend to be more aggressive so the earlier they are picked up the better.
“And as more genetic information becomes available, the efficiency of screening approach that takes account of genetic risk will further improve”.
The researchers also calculated a statistical model of how a similar approach might be relevant to prostate cancer screening if a programme were to be introduced in the UK.
Professor Paul Pharaoh, a Cancer Research UK expert in genetics and study author, said: “Even though our analysis is based on a theoretical model which assumes that there’s a 100 per cent attendance for breast cancer screening it still shows that personalised screening has the potential to reduce the disadvantages of a screening programme without losing any of its benefits. We now need more research to find out what effect genetic testing would have on over-diagnosis and whether deaths from breast cancer would fall. And we also need to consider the wider ethical and legal issues with more personalised screening”.
1. Polygenic susceptibility to prostate and breast cancer: implications for personalised screening N Pashayan, S W Duffy, S Chowdhury, T Dent, H Burton, D E Neal, D F Easton, R Eeles, P Pharoah
British Journal of Cancer doi:10.1038/bjc.2011.118
Notes to Editor
2. This model can be adapted to explore different outcomes depending on the risk threshold. As you increase the risk threshold, fewer women would be screened but a higher proportion of cancers would be detected within this group as women with higher risk are being screened;
- Screening depending on risk threshold of 2 per cent: 2 per cent fewer women would be screened and the same number of cancer cases would be detected.
- Screening depending on risk threshold of 2.02 per cent: the same number of women would be screened as the age based screening programme but the number of screen detected cases would be 1 per cent greater.
- Screening depending on a risk threshold of 2.5 per cent: leads to screening 50 per cent of women aged 35- 79 years old with 73 per cent of cases detected. This means a larger proportion of women from a smaller age range will be detected by screening.
With more knowledge about different gene types less women would need to be screened.
3. This method was based on a hypothetical screening scenario screening women from 35 to 79 and should not be compared to the current NHS national screening programme because the researchers have assumed that 100 per cent of women will attend screening and all possible cancers will be identified to simplify the calculations.
In England almost 31,000 cases of breast cancer are diagnosed in women aged 35 to 79.
In the UK in 2008 almost 47,700 women were diagnosed with breast cancer
In 2008 in the UK around 12,000 women and around 70 men died from breast cancer.