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Researchers explore the effectiveness and cost-effectiveness of cervical cancer screening

Pap smears, which detect preinvasive and early invasive cervical cancer, reduced the incidence of this cancer in the United States by 43 percent and reduced deaths from the disease by 46 percent over the last two decades. The U.S. Food and Drug Administration recently approved several new screening technologies intended to reduce false-negative results of conventional Pap smears (smears that indicate no cancer in women who have cervical cancer). Three new studies, supported by the Agency for Healthcare Research and Quality, examine the effectiveness and cost-effectiveness of these screening tests.

The first study (AHRQ contract 290-97-0014) shows that new screening technologies with increased sensitivity are more costly than conventional Pap smears. The second study (AHRQ grant HS07373) concludes that a 3-year screening interval could be as effective as yearly screening in women who have a previous normal Pap smear. The third study (AHRQ grant HS08395) finds that cognitive strategies are the best way to improve women's compliance with followup of abnormal Pap smear screening tests. The three studies are summarized here.

Myers, E.R., McCrory, D.C., Subramanian, S., and others (2000, November). "Setting the target for a better cervical screening test: Characteristics of a cost-effective test for cervical neoplasia screening," Obstetrics & Gynecology 96(5), pp. 645-652.

According to this study by the AHRQ-supported Evidence-based Practice Center at Duke University, technologies that increase sensitivity of cervical cytologic screening also increase overall costs. This is true even if the cost of the technology is identical to that of conventional Pap smears. Apparently, the more sensitive tests uncover a high prevalence of low-grade lesions, which rarely lead to cancer but do prompt further costly testing.

In this study, the researchers used a model that included various costs and screening intervals. For example, if a new technology had no extra cost per slide compared with conventional Pap tests, increasing sensitivity was cost-saving with 3-year screening intervals if the cost of evaluating and treating low-grade squamous intraepithelial lesions (SILs) was $550. That was the only variable and only screening frequency that resulted in a cost savings. At any marginal per slide cost above $3, increasing sensitivity was not cost saving even if the cost of treating low-grade SILs was $0.

Efficient cervical cancer screening requires methods with greater specificity for detecting lesions that are most likely to become cancerous (that is, high-grade lesions). In fact, new, more sensitive technologies are likely to be cost effective compared with Pap smears only if they are associated with improved specificity, permit decreased screening frequency, or are used in conjunction with less expensive treatments of low-grade lesions. New tests based on specific types of human papillomavirus (HPV), which is associated with development of cervical cancer, or that use biomarkers might meet all three requirements, according to the researchers.

They used a model of the natural history of cervical cancer to estimate the effects of sensitivity, specificity, and screening frequency on cost-effectiveness of screening for cervical cancer. The model was based on the assumption that all cervical cancer arises from infection with HPV, which progresses sequentially from low-grade through high-grade SILs to invasive cervical cancer.

Sawaya, G.F., Kerlikowski, K., and Lee, N.C. (2000, August). "Frequency of cervical smear abnormalities within 3 years of normal cytology." Obstetrics & Gynecology 96(2), pp. 219-223.

Annual cervical cancer screening has been standard practice for many years, and doctors are reluctant to change a screening system that has been highly effective in controlling cervical cancer. However, this study suggests that screening every 3 years might be sufficient. These researchers found that within 3 years after normal Pap smear results, cervical smears interpreted as high-grade squamous intraepithelial lesions (SILs) or worse were uncommon. Also, women screened 1, 2, and 3 years after normal Pap smears had the same risk of developing high-grade SILs or worse.

The researchers studied a group of 128,805 women at community-based clinics throughout the United States who were screened for cervical cancer within 3 years of normal smears. They determined the incidence of cytologic abnormalities defined as atypical squamous cells of undetermined significance (ASCUS), low-grade SILs (unlikely to develop into cancer), and high-grade SILs or suggestive of squamous cell cancer. Age-adjusted incidence rates of high-grade SILs or worse were similar for women screened at 9 to 12 months (25 of 10,000), 13 to 24 months (29 of 10,000), and 25 to 36 months (33 of 10,000) after normal Pap smears. Age-adjusted incidence rates of ASCUS, the most common cytologic abnormality, did not change.

Incidence of smears interpreted as low-grade SILs increased as time from the normal smear increased. Low-grade SILs are usually of no clinical importance, but they do prompt further costly tests and procedures that cause unfounded patient anxiety. The risks of overscreening should be balanced against its benefits to develop optimal screening strategies for women with recent normal Pap smears, conclude the authors.

Yabroff, K.R., Kerner, J.F., and Mandelblatt, J.S. (2000). "Effectiveness of interventions to improve follow-up after abnormal cervical cancer screening." Preventive Medicine 31, pp. 429-439.

For cervical cancer screening to be effective, women who have an abnormal Pap smear must return to receive followup, timely diagnosis, complete cancer staging, and appropriate treatment. Unfortunately, many women fail to receive timely, or for that matter any, resolution of an abnormal screen. In fact, between 7 and 49 percent of women with abnormal Pap smear tests do not receive appropriate followup. Either they face financial barriers, fear diagnostic procedures or diagnosis, or misinterpret or receive inadequate communication from doctors about test results and conclude the results are normal.

The authors performed a meta-analysis of studies of cognitive, behavioral, or sociologic interventions intended to improve followup after an abnormal cervical cancer screening test. Cognitive strategies such as telephone counseling or pamphlets provided new information and education, increased existing knowledge, and clarified misperceptions. Behavioral interventions, such as mailed and telephone reminders, altered cues or stimuli associated with followup behavior. Finally, sociologic interventions used social norms or peers to increase compliance.

According to this study, cognitive interventions using interactive telephone counseling were the most effective, improving compliance by 24 to 31 percent. Behavioral interventions, such as patient reminders, were also effective, increasing followup to 18 percent. The single sociologic intervention used videotaped peer discussions to provide a message about abnormal Pap smears and appropriate followup, but it was not associated with increased followup after an abnormal test.

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