News
Computer model highlights benefits and risks of cervical cancer
screening methods
6 October 2008
In an analysis based on a computer model, it appears that comparing
the benefits and risks of different cervical cancer prevention
approaches may help women and their doctors choose appropriate screening
strategies, according to a report in the September 22 journal
Archives of Internal Medicine, one of the JAMA/Archives journals.
Routine screening with cervical cytologic testing, commonly known as
Pap smears, is credited with reducing the incidence of cervical cancer
through the early detection of abnormal cells, according to background
information in the article. Today, US women have an average lifetime
cervical cancer risk of 0.7 percent. Recently, even more sensitive DNA
testing for the human papillomavirus (HPV), which contributes to
cervical cancer, has become available, along with vaccines against HPV.
This leaves women and their physicians with several prevention options
and considerations.
Dr Natasha Stout, and colleagues at the Harvard School of Public
Health, Boston, used a computerised simulation model of cervical cancer
in the United States to assess the benefits and risks associated with
various screening strategies. The strategies differed by type of primary
screening test, process for handling abnormal results and screening
frequency. “These strategies pose trade-offs between minimising cancer
risk (already small with regular screening) and minimising the risk of
false-positive test results and excessive diagnostic procedures,” the
authors write.
Differences in women’s lifetime cancer risk varied little between
screening strategies; however, the difference between the strategy
offering the least and most frequent referrals for colposcopy (a
procedure in which physicians look directly at the cervix through a
microscope) was three-fold.
For a representative group of 1,000 20-year-old women undergoing
annual screening for 10 years, combined cytologic and HPV testing would
lead to an estimated 1,795 referrals for colposcopy and other follow-up
procedures (1,788 of them excessive, or not associated with cancer). The
same women would receive 403 referrals (396 excessive) from cytologic
testing following by triage HPV testing for those with abnormalities;
333 referrals (326 excessive) from conventional cytologic testing; and
223 referrals (216 excessive) from HPV testing followed by cytologic
triage testing.
“For women who experience short-term anxiety around screening and
diagnostic workup, quality of life could be an important criterion for
decision making if several screening options associated with similar
cancer risk reduction are available,” the authors write. “Using
cytologic testing followed by triage testing in younger women minimises
both diagnostic workups and positive HPV test results, whereas in older
women diagnostic workups are minimised with HPV DNA testing followed by
cytologic triage testing.”
“There is great promise in the availability of accurate HPV
diagnostics, new screening technology and HPV vaccination for successful
cervical cancer prevention in the United States. From both an individual
and population perspective, the range of new options for prevention will
ideally be assembled in such a way as to improve cancer outcomes, reduce
disparities and minimise the risk of overdetection of abnormalities
likely to resolve on their own,” they conclude.
“These results provide an initial step toward a comprehensive set of
clinically relevant information highlighting trade-offs among screening
policies to ultimately better inform women’s decisions and provide
additional dimensions for the construction of clinical guidelines.”
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