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More Sensitive, Less Frequent Cervical Cancer Screening

Although cervical cancer screening has been available for more than 20 years, about 12,800 new cases were diagnosed and 4,500 related deaths occurred in the United States in the year 2000. Screening can reduce mortality rates by 46 percent, but advanced cases still occur because of false-negative screening test results. New screening techniques that involve liquid-based cytology (LBC) and testing for human papillomavirus (HPV) offer more sensitive screening that may allow for a longer interval between tests. Maxwell and colleagues analyzed the costs and outcomes of new screening methods for cervical cancer to determine the optimal type and interval of screening tests for use in large populations of healthy women.

They developed a Markov model, based on the natural history of HPV infection and the etiology of cervical cancer, and applied the model to a theoretic cohort of 100,000 healthy women beginning at 18 years of age and lasting until 85 years. In this cohort, the model was used to predict the cervical cancer mortality and costs associated with three methods of screening (i.e., conventional Papanicolaou [Pap] screening, LBC screening alone, and LBC plus HPV). For each technique, they estimated the implications of screening every year and compared this with screening at two- and three-year intervals.

With no available screening, an estimated 1,001 deaths attributable to cervical cancer would occur in the cohort population. Even the simplest option, conventional Pap screening every three years, reduced this rate to 189 deaths. Pap screening at two- and one-year intervals was estimated to result in 116 and 40 deaths, respectively (see the accompanying table).

Office Visits, Abnormal Pap Tests, and Cancer-Related Outcomes Strategy Total visits for screening, diagnosis, and treatment of preinvasive disease Total abnormal Pap tests Total Pap test with given abnormality Total cancer cases Percentage stage I Total cancer deaths ASCUS LSILs HSILs+ No screening -- -- -- -- -- 2,968 46.3 1,001 Conventional Pap test everythree years 1,787,226 96,117 36,745 46,948 12,424 857 69.6 189 LBC + HPV every three years 1,810,541 186,330 80,471 85,443 20,416 393 84.7 73 LBC every three years 1,894,453 189,841 81,080 87,712 21,049 430 84.2 80 Conventional Pap test everytwo years 2,604,359 135,160 52,979 66,154 16,027 573 75.6 116 LBC + HPV every two years 2,631,705 261,139 115,831 118,522 26,786 213 90.5 37 LBC every two years 2,754,898 267,938 117,060 123,042 27,836 244 90.1 42 Conventional Pap test every year 5,232,754 247,978 102,840 119,386 25,752 219 85.1 40 LBC + HPV every year 5,264,348 481,959 225,914 210,330 45,715 39 96.0 6 LBC every year 5,513,415 501,279 229,581 223,618 48,080 51 95.7 8 Pap = Papanicolaou; ASCUS = atypical squamous cells of undetermined significance; LSIL = low-grade squamous intraepithelial lesion; HSIL = high-grade squamous intraepithelial lesion; LBC + HPV = liquid-based cytology with reflex human papillomavirus testing using Hybrid Capture 2 for ASCUS results. Adapted with permission from Maxwell GL, Carlson JW, Ochoa M, Krivak T, Rose GS, Myers ER. Costs and effectiveness of alternative strategies for cervical cancer screening in military beneficiaries. Obstet Gynecol 2002;100:745.

The cost-effectiveness of the different strategies depended on the screening interval. As the test sensitivity rises, the specificity tends to decrease, resulting in more costs to manage false-positive results. Both conventional Pap smears and LBC become cost-effective when performed every three years. When all associated follow-up and treatment costs are taken into consideration, LBC plus HPV screening every three years costs less than $50,000 per year of life saved.

The authors conclude that the most sensitive cervical screening tests, LBC or LBC plus HPV testing, are cost-effective when performed at three-year intervals but not when performed annually.

ANNE D. WALLING, M.D.

Maxwell GL, et al. Costs and effectiveness of alternative strategies for cervical cancer screening in military beneficiaries. Obstet Gynecol October 2002;100:740-8.

EDITOR'S NOTE: If our understanding of the pathophysiology is correct, no woman should die of cervical cancer. The realities of human behavior mean we can never completely prevent sexually transmitted diseases, although we continue to advise patients about this and other lifestyle factors, such as smoking, that seem to play some role in vulnerability to invasive cervical cancer. Improved testing techniques can be effective only if we ensure their use. What are we doing to ensure that any screening is available to uninsured women and women in vulnerable groups who find current health services too difficult to access? What are we doing to remind all women to be screened regularly? Will switching to screening every three years be more difficult to remember, thus decreasing the effectiveness? Cervical cancer seems to lack the public and political clout of breast cancer, yet it offers great scope for reduction in case fatality. Perhaps it is time to mobilize the publicity machine as well as to pay attention to all aspects of our own practices that could contribute to minimizing the impact of this horrible disease.--A.D.W.

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