Risk of Cervical Cancer Associated With Extending the Interval Between Cervical-Cancer Screenings

Abstract

Using the database of the National Breast and Cervical Cancer Early Detection Program of the Centers for Disease Control and Prevention (CDC) for the years 1991 to 2000, the authors investigated the risk of cervical cancer associated with longer screening intervals. The Markov model of the natural history of cervical cancer was used to estimate the numbers of cervical screenings and colposcopic examinations required to detect one case of cancer in any one screening interval. Cervical cytology was available for 938,576 women less than 65 years of age. Histologic results were from cervical biopsy, usually performed during a colposcopic examination. Fifty-four percent of the women were between 45 and 65 years of age. They identified themselves as white or nonwhite in equal numbers. Table 1 presents the results of cervical biopsy in the study group. The percentage of women diagnosed with grades 1, 2, and 3 cervical intraepithelial dysplasia (CIN) after 0, 1, or 2 negative cervical tests, respectively, was highest in women under 30 years of age. After 3 or more negative tests, women 30 to 44 years of age had the highest percentage of diagnoses of grades 1, 2, or 3 CIN. There was no invasive cervical cancer seen in women of any age group after 3 or more consecutive negative cervical smears. Less than 0.01% of women who had 1 or 2 consecutive negative tests were diagnosed with cervical cancer. Approximately 1 in every 1800 women who had not previously had a negative cervical smear in a CDC screening was found to have invasive cervical cancer. The risk of invasive cervical cancer decreased with advancing age and increasing numbers of consecutive negative cervical smear results. The Markov model predicted that women age 30 to 44 had a 5 in 100,000 risk of developing invasive disease after 3 consecutive negative screenings. The risk for women aged 45 to 59 years was 2 in 100,000, and for women 60 to 64 years of age, the risk was 1 in 100,000 after 3 negative smears. Compared with screening every 3 years after the last negative test, in 100,000 women, 1 additional case of invasive cervical cancer could be detected in women 30 to 44 years of age, given annual screening and an additional 69,665 cervical smears and 3861 colposcopic examinations. For women 45 to 59 years of age, with annual screening, an additional 209,324 cervical tests and 11,502 colposcopic examinations would be required to detect 1 additional case of invasive cervical cancer.