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The percentage of positive results from breast cancer screening has risen in the United Kingdom, but almost a quarter of screening centres are recalling more than one in 10 women for further assessment, often because the initial results were unclear.
Researchers from the Institute of Cancer Research say that variation among individual screening units, especially in the number of women being recalled, should be investigated, as the extra workload for units that recall a high proportion of women will add to other pressures facing the programme.
Pressure of work means that many centres are failing to meet the target of 90% of women being offered an appointment within 36 months of their previous routine screen, the researchers say (Journal of Medical Screening 2007;14:200-4).
Their report gives results from the UK NHS breast screening programme for 1999 to 2005. These show that uptake of screening remained stable over the six years. On average, 75% of women aged 50 to 54 years took up a first invitation to undergo screening, and 89% of women aged 50-64 years who had undergone screening took up an invitation for further screening. In 2005 uptake at first invitation among women aged 50 to 54 ranged across centres from 50% to 85%, while uptake of subsequent screening among women aged 50-64 ranged from 73% to 93%.
The average rates of recall over the six years were 9% among women who had attended for a first screening and 4% among women who underwent a subsequent screen. In 2005 just over a fifth (22%) of units recalled more than 10% of women for assessment after their first screen.
The proportion of cancers detected at the first screening test rose by 14% from 2000 to 2005, from 6.3 to 7.2 cases per 1000 women. The rate of detection of small (<10 mm) invasive cancers detected at a subsequent screen rose by 40% from 2000 to 2005, from 1 per 1000 to 1.4 per 1000.
“These results show that the programme is performing well against the targets,” the authors wrote.
Workload affected the timing of invitations for screening, the authors said. “With all units in England, Wales and Northern Ireland now using two-view mammography, and more units now inviting women aged between 65 and 70 years, the pressure on the programme continues, with many units failing to meet the target of 90% of women being offered an appointment within 36 months of their last routine screen.”
They said that the expanding role of the advanced practitioner will help ease the strain. They also said that most units read mammograms twice and that many use a radiographer as the second reader.
“Experimental evidence has shown that, after adjusting for reading volume and experience, radiographers read as well as radiologists,” says the report. “Consequently, a number of pilot units are currently using only radiographers to read mammograms, with any discordant opinions being arbitrated by a clinician.
“Results from this study, along with those looking at technologies associated with digital mammography such as the use of computer-aided detection systems, will help inform how screening for breast cancer in the UK can be delivered in the future.”