Screening programmes aim to detect cancer at an early stage when treatment may be more effective and less intense. In the UK, there are well-established programmes in breast and cervical cancer; more recently, programmes have been developed to detect bowel cancer. In some countries, including the UK, these are national programmes with lower and upper age limits which reflect the evidence base for benefits.
Much of the uncertainty around the use of screening tests in older people results from a lack of randomized controlled trials (RCTs) conducted in this population, requiring extrapolation of data on effectiveness from younger patients. Furthermore, most do not account for individual patient characteristics, such as levels of comorbidity, frailty or functional status, which may alter the likelihood of benefit or harm from screening. Additionally, ageing results in a shorter life expectancy; thus, older patients are more likely to die with their cancer rather than from it.
This chapter summarizes the current situation for breast cancer screening, which has been established in the UK since 1988, and prostate cancer screening, which is not yet the subject of a national screening programme. These two subjects provide useful insights into the advantages and disadvantages of cancer screening programmes in the older population.
Screening for breast cancer
The Forrest report published in 19861 led to the establishment of the NHS national breast cancer screening programme in 1988. This report was based on a number of international RCTs and it recommended screening by x-ray mammography on a 3 yearly basis between the ages of 50 and 65 years. However, subsequent long-term follow-up and observational studies raised concerns relating to the risks and benefits of breast cancer screening, leading to claims that there was no reliable evidence that mammographic screening decreases breast cancer mortality and that such screening programmes could not be justified.2 Over the following decade there was increasing debate surrounding breast cancer screening and in 2012 an independent review chaired by Sir Michael Marmot was commissioned in the UK to focus on the beneficial effect of breast cancer screening on mortality and also the risk of overdiagnosis and other harms.3 The review concluded that screening results in a 20% reduction in breast cancer mortality amongst women invited to the breast cancer screening programme but that there is considerable uncertainty around this estimate (Figure 12.1). This benefit equates to approximately one breast cancer death prevented for every 180 women who attend breast cancer screening within the 50-70 year age group, i.e. the prevention of approximately 1300 breast cancer deaths each year. The review also concluded that overdiagnosis - the detection of cancers which might never have become symptomatic - does occur and represents approximately 20% of cancers detected in women invited for screening. There are thus three cases of overdiagnosis and treatment for every individual ...