Page 42 - Screening for Cervical Cancer: Systematic Evidence Review
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Chapter III. Results
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1,000 person-years among women 40 years of age and older; 1.4 per 1,000 women ages 50 to
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64 years and 0.8 per 1,000 women 65 and older screened at an interval of 36 months or less;
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0.6 to 1.9 per 1,000 smears in women ages 50 to 59 years; 0.2 to 1.2 in women 60 or older; and
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0.4 per 1,000 women in a post-menopausal cohort with average age of 66. Fewer than one
woman in a thousand (in some studies as few as two to six in 10,000) who were age 60 and older
and had a negative smear at baseline received a new diagnosis of CIN 3 or cancer. In studies that
had cases of cancer in screened populations of older women, the ratio of CIN 3 to cancer range
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from 4 to 1 to more than 10 to 1.
Prevalence
Studies of prevalence (i.e., those that include screened and unscreened women without
requirement of baseline normal cytology) are also compatible with the assertion that risk of high-
grade cervical abnormalities decreases with age. The only study that does not appear to support
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this view is that of Formso and colleagues; they report 2.23 cytologic findings of CIN 3 per
1,000 women age 50 to 59 years; 1.96 per 1,000 for women age 60 to 69 years; and 4.24 for
women ages 70 and older. The inclusion criteria specified no prior abnormal Pap test; this
allowed inclusion of women having their first screening ever or after an extended interval. In the
text, the authors noted the large proportion of older women, especially those older than 70, who
had first Pap tests included in these data. Their data are based on records from the same
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cytology laboratory in Norway used by Gram et al. The laboratory serves a relatively stable
population in two northern counties without a formal screening program. The time periods in the
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analyses by Formso et al. and Gram et al. overlap by two years; thus, presumably individual-
level data may be duplicated in these reports. Gram and colleagues sought histologic
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