Hysterectomy Prevalence and Death Rates for Cervical Cancer -- United States, 1965-1988

Since the 1960s, hysterectomy has been one of the most frequently performed inpatient surgical procedures in the United States, with an estimated 33% of women undergoing a hysterectomy by 60 years of age (1). However, rates of cervical cancer mortality that do not allow for the proportion of women with hysterectomies in the population will underestimate the rates in the true at-risk population (i.e., women with intact uteri) and may influence apparent secular trends in rates of cervical cancer mortality (2). This report uses national mortality and hospital-discharge data to compare death rates, corrected and uncorrected for hysterectomy prevalence, for women who died with an underlying diagnosis of cervical cancer (International Classification of Diseases, Ninth Revision (ICD-9) and ICD-9-Clinical Modification, code 180) (3).

To determine the effect of hysterectomy prevalence on death rates* for cervical cancer, age-specific proportions of women in the United States with intact uteri from 1965 through 1988 were estimated using data from CDC's National Hospital Discharge Survey (NHDS) (4). Because the secular decline in death rates for cervical cancer appeared similar before and after correcting for hysterectomy prevalence (Figure 1), linear regression models were used to assess the effect of hysterectomy prevalence on the trend in rates of cervical cancer mortality. These models used logarithmic transformations of corrected and uncorrected rates as dependent variables (5) (Table 1).

The prevalence of women with hysterectomies accounted for 8% of the decrease since 1965 in total age-adjusted death rates (Table 1). However, the difference in average annual rate of change for the 24-year period was not statistically significant (p=0.07). The largest effect was for women aged 40-69 years, for whom 11% of the decrease could be attributed to hysterectomies (p=0.06).

Excluding women without intact uteri from the at-risk population, the cervical cancer death rate in 1965 increased from 7.9 to 10.6 per 100,000 women; in 1988, these rates were 3.0 and 4.3 per 100,000, respectively. During the 24-year period, annual corrected rates were an average of 39% greater than uncorrected rates (Table 1). The relative difference in the corrected and uncorrected rates increased significantly with age, from a 10% differential for women aged 20-39 years to a 56% differential for women greater than or equal to 70 years of age (p for heterogeneity less than 0.001). Reported by: Epidemiology and Statistics Br, Div of Cancer Prevention and Control, National Center for Chronic Disease Prevention and Health Promotion; Hospital Care Statistics Br, Div of Health Care Statistics, National Center for Health Statistics, CDC.

Editorial Note

Editorial Note: The decline in death rates for cervical cancer in the United States is generally attributed to use of the Papanicolaou (Pap) test (6). However, because the Pap test has never been evaluated in a randomized clinical trial, some investigators have questioned its value in reducing mortality and have proposed that increasing rates of hysterectomy could account for this decline (7). Although findings in this report suggest that including women who have had hysterectomies artificially lowers death rates, only 8% of the mortality decline since 1965 can be attributed to this inclusion. Incidence and death rates for cervical cancer increase with age, and the greatest effect of previous hysterectomies on death rates was among elderly women; however, Pap test screening incidence rates decrease with age (8).

The approach used in this analysis has at least two limitations. First, this analysis assumed that a woman who has had a hysterectomy is not at risk for dying from cervical cancer. However, a woman who underwent a hysterectomy for cervical cancer but who subsequently died from the disease would have been included in the numerator for rate calculation but inappropriately excluded from the denominator, thereby inflating the estimate for the effect of hysterectomy prevalence on cervical cancer death rates. In this analysis, this effect was likely to have been limited; hysterectomies for cervical malignancies would have little effect on the corrected death rates because less than 2% of all hysterectomies are performed for cervical cancer (1). Second, this analysis could not adequately evaluate regional and racial differences in the rate of hysterectomy because of limitations of the sample size (1), and this variability could be associated with differential effects on cervical cancer mortality over time.

The substantial increase in rates of cervical cancer mortality for elderly women after correcting for hysterectomy prevalence (Table 1) highlights the inadequate screening of older women with intact uteri. The American Cancer Society recommends annual Pap tests from the onset of sexual activity or from age 18; after three consecutive negative tests, the physician may recommend less frequent testing (9). This recommendation contains no upper age limit on testing. Because declines in cervical cancer mortality are not artifacts of increasing rates of hysterectomy and can be attributed largely to use of the Pap test, additional cervical cancer mortality may be prevented by greater compliance with recommended Pap test guidelines.

To further reduce cervical cancer mortality in the United States, national health objectives for the year 2000 include increasing to at least 95% the proportion of women aged greater than or equal to 18 years** with uterine cervix who have ever received a Pap test; for women aged greater than or equal to 18 years, increasing to at least 85% those who received a Pap test within the preceding 1-3 years (70% for women aged greater than or equal to 70 years); and reducing death from cancer of the uterine cervix to no more than 1.5 per 100,000 women*** (10).

References

1. Pokras R, Hufnagel VG, NCHS. Hysterectomies in the United

States, 1965-84. Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, 1987; DHHS publication no. (PHS)87-1753. (Vital and health statistics; series 13, no. 92).

2. Lyons JL, Gardner JW. The rising frequency of hysterectomy: its effect on uterine cancer rates. Am J Epidemiol 1977;105:439-43.

3. NCHS. Compressed mortality file (machine-readable public-use data tape). Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, 1965-1988.

4. NCHS. National Hospital Discharge Survey, 1965-1988: (Diskette provided by the Hospital Care Statistics Branch). Hyattsville, Maryland: US Department of Health and Human Services, Public Health Service, CDC, 1991.

5. Neter J, Wasserman W. Applied linear statistical models. Homewood, Illinois: Richard D. Irwin, Inc, 1974;123-8.

6. Koss LG. The Papanicolaou test for cervical cancer detection: a triumph and a tragedy. JAMA 1989;261:737-43.

7. McCormick JS. Cervical smears: a questionable practice? Lancet 1989;2:207-9.

8. CDC. Provisional estimates from the National Health Interview Survey supplement on cancer control--United States, January-March 1987. MMWR 1988;37:417-20,425.

9. American Cancer Society. Summary of current guidelines for the cancer-related checkup: recommendations. Atlanta: American Cancer Society, 1988; ACS publication no. 3347.01-PE. 10. Public Health Service. Healthy people 2000: national health promotion and disease prevention objectives--full report, with commentary. Washington, DC: US Department of Health and Human Services, Public Health Service, 1991; DHHS publication no. (PHS)91-50212.

• Age-adjusted to the 1970 U.S. population.

** Baseline in 1987: 88% "ever" and 75% "within the preceding 3 years" and for women aged greater than or equal to 70 years, 76% "ever" and 44% "in the preceding 3 years." *** Age-adjusted to the 1970 U.S. population.

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