Extending the Interval between Cervical-Cancer Screenings
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《新英格兰医药杂志》
To the Editor: Although the conclusion of the article by Sawaya et al. on the interval between cervical-cancer screenings (Oct. 16 issue)1 may be correct, they failed to note one of the large biases. They presumed the same sensitivity and specificity for colposcopy whether the abnormal Papanicolaou test had been preceded by one or more years without a Papanicolaou test. A finding of grade 2 or grade 3 cervical intraepithelial neoplasia on colposcopic biopsy in a patient who has not had a Papanicolaou test for three years is more likely to be an invasive cancer on cold-knife conization than is the case for a patient who had a normal result or even an abnormal result on a Papanicolaou test the previous year.
Peter W. Rufleth, M.D.
6 Main St.
Hyannis, MA 02601
prufleth@hotmail.com
References
Sawaya GF, McConnell KJ, Kulasingam SL, et al. Risk of cervical cancer associated with extending the interval between cervical-cancer screenings. N Engl J Med 2003;349:1501-1509.[Abstract/Full Text]
The authors reply: It is possible that some women with at least three prior normal tests and high-grade cervical intraepithelial neoplasia were ultimately given a diagnosis of cancer on the basis of conization; this likelihood may increase as the time between the previous normal test and the abnormal test prompting colposcopy increases. In our study, this interval ranged from 9 to 36 months. Since only 16 of 32,320 women were in this diagnostic category, the number of potentially missed cancers would be small; invasive cancer is rare in women with normal results on recent screening tests1,2 and is uncommonly diagnosed at the time of conization.3,4
In This Week in the Journal5 our article is described as concluding that "screening performed once every three years is associated with an excess risk of cervical cancer of no more than 3 in 100,000." This statement requires clarification. "Every three years" implies a lifetime screening periodicity; we reported only the estimated excess risk associated with extending the screening interval for a single three-year period (which we estimated at 3 in 100,000). Lifetime screening every three years, as compared with every year, can be expected to have excess-risk estimates greater than 3 per 100,000. Projecting outcomes further in the future, however, requires accounting for competing causes of mortality and diminishing differences in risk that we noted between screening strategies as women age. The next steps in formulating rational health care policies include performing cost-effectiveness and cost–utility analyses to identify screening strategies that maximize benefits and minimize costs and harm.
George F. Sawaya, M.D.
University of California, San Francisco
San Francisco, CA 94118
Shalini Kulasingam, Ph.D.
Duke University
Durham, NC 27710
Herschel Lawson, M.D.
Centers for Disease Control and Prevention
Atlanta, GA 30341
References
Janerich DT, Hadjimichael O, Schwartz PE, et al. The screening histories of women with invasive cervical cancer, Connecticut. Am J Public Health 1995;85:791-794.
Sung HY, Kearney KA, Miller M, Kinney W, Sawaya GF, Hiatt RA. Papanicolaou smear history and diagnosis of invasive cervical carcinoma among members of a large prepaid health plan. Cancer 2000;88:2283-2289.
Andersen ES, Nielsen K, Pedersen B. The reliability of preconization diagnostic evaluation in patients with cervical intraepithelial neoplasia and microinvasive carcinoma. Gynecol Oncol 1995;59:143-147.
Costa S, Nuzzo MD, Rubino A, et al. Independent determinants of inaccuracy of colposcopically directed punch biopsy of the cervix. Gynecol Oncol 2003;90:57-63.
This week in the Journal. N Engl J Med 2003;349:1493-1493.
Peter W. Rufleth, M.D.
6 Main St.
Hyannis, MA 02601
prufleth@hotmail.com
References
Sawaya GF, McConnell KJ, Kulasingam SL, et al. Risk of cervical cancer associated with extending the interval between cervical-cancer screenings. N Engl J Med 2003;349:1501-1509.[Abstract/Full Text]
The authors reply: It is possible that some women with at least three prior normal tests and high-grade cervical intraepithelial neoplasia were ultimately given a diagnosis of cancer on the basis of conization; this likelihood may increase as the time between the previous normal test and the abnormal test prompting colposcopy increases. In our study, this interval ranged from 9 to 36 months. Since only 16 of 32,320 women were in this diagnostic category, the number of potentially missed cancers would be small; invasive cancer is rare in women with normal results on recent screening tests1,2 and is uncommonly diagnosed at the time of conization.3,4
In This Week in the Journal5 our article is described as concluding that "screening performed once every three years is associated with an excess risk of cervical cancer of no more than 3 in 100,000." This statement requires clarification. "Every three years" implies a lifetime screening periodicity; we reported only the estimated excess risk associated with extending the screening interval for a single three-year period (which we estimated at 3 in 100,000). Lifetime screening every three years, as compared with every year, can be expected to have excess-risk estimates greater than 3 per 100,000. Projecting outcomes further in the future, however, requires accounting for competing causes of mortality and diminishing differences in risk that we noted between screening strategies as women age. The next steps in formulating rational health care policies include performing cost-effectiveness and cost–utility analyses to identify screening strategies that maximize benefits and minimize costs and harm.
George F. Sawaya, M.D.
University of California, San Francisco
San Francisco, CA 94118
Shalini Kulasingam, Ph.D.
Duke University
Durham, NC 27710
Herschel Lawson, M.D.
Centers for Disease Control and Prevention
Atlanta, GA 30341
References
Janerich DT, Hadjimichael O, Schwartz PE, et al. The screening histories of women with invasive cervical cancer, Connecticut. Am J Public Health 1995;85:791-794.
Sung HY, Kearney KA, Miller M, Kinney W, Sawaya GF, Hiatt RA. Papanicolaou smear history and diagnosis of invasive cervical carcinoma among members of a large prepaid health plan. Cancer 2000;88:2283-2289.
Andersen ES, Nielsen K, Pedersen B. The reliability of preconization diagnostic evaluation in patients with cervical intraepithelial neoplasia and microinvasive carcinoma. Gynecol Oncol 1995;59:143-147.
Costa S, Nuzzo MD, Rubino A, et al. Independent determinants of inaccuracy of colposcopically directed punch biopsy of the cervix. Gynecol Oncol 2003;90:57-63.
This week in the Journal. N Engl J Med 2003;349:1493-1493.