Cervical screening in England is recommended every three years for women aged 25 to 49 and every five years for women aged 50 to 65. The idea behind cervical screening is to take a sample of cells from a woman’s cervix (a smear test) and look for changes in the cells that could develop into cervical cancer if left untreated (these are often called pre-cancers).
If changes are found, there are good treatments available to remove the cells. Previously, some women were called back for follow-up tests for 10 or more years after treatment, to make sure the cells in the cervix were still healthy and that there were no signs of cancer or other health problems.
Recently, in England, the NHS Cancer Screening Programmes has decided to change these recommendations and add another follow-up test, called the HPV test. The HPV test checks for genetic material (DNA) from the virus, to see whether a woman is infected with HPV strains that can cause cancer. Like a smear test, HPV tests are done on samples of cells collected from the cervix.
So, instead of being called in repeatedly for more tests, some women who have had smear tests have another test, for the HPV virus. If HPV is not found, then a woman doesn’t need to be tested again for another three years. If the test does find HPV, women are referred for more testing and possible treatment.
Studies show that HPV tests can detect more women with pre-cancers than smear tests. This could lead to fewer women developing cervical cancer as well as the most advanced type of pre-cancer, called CIN3+. In the new study researchers calculated how many women would get CIN3+ both with and without HPV testing.
In a cervical screening programme that didn’t include HPV testing, 29 in every 1,000 women who had pre-cancer treatment would have a CIN3+ within 10 years of treatment.
Adding HPV testing would mean 21 in every 1,000 women who were treated for pre-cancers would have a CIN3+ within 10 years.
This means adding HPV testing to the cervical screening programme avoids around eight women having a CIN3+ pre-cancer for every 1,000 women treated.
How reliable is the research?
The researchers used computer modelling to estimate how many women would have treatment in each scenario. Using computer modelling relies on the researchers making certain kinds of assumptions about how the cervical screening programme works, as well as women’s risks of cervical cancer. For example, the researchers assumed that at least 95 in 100 women are successfully treated for pre-cancer, and that 16 in 100 women who have been successfully treated would have a positive HPV test after six months. These assumptions are based on results of previous studies, but we can’t be sure whether they accurately reflect the screening programme. If they are not accurate, this would affect the results.
What does this mean for me?
This study seems to support the addition of HPV testing to the NHS cervical screening programme, for the follow-up of women treated for pre-cancer. But we have to be cautious about its findings, as they are based on computer modelling, and not studies involving real people. HPV testing is being rolled out as part of the cervical screening programme in England and this process began last year.
The researchers say we still need more studies comparing the different screening methods - with and without HPV testing - to be sure of the benefits for women after treatment.
Legood R, Smith M, Lew J-B, et al. Cost effectiveness of human papillomavirus test of cure after treatment for cervical intraepithelial neoplasia in England: economic analysis from NHS Sentinel Sites Study. BMJ. Published online 2 November 2012.
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