Risk variables affecting high-grade Pap smears at second visit: effects of screening interval, year, age and low-grade smears

Effectiveness of an organized cervical cancer screening program in Korea: results from a cohort study

Although the value of cervical cancer screening is widely acknowledged, the effectiveness of an organized cervical cancer screening program in Korea has never been evaluated. We investigated the associations of the frequency of cervical cancer screening with cervical cancer incidence using data from a large prospective cohort study. In this analysis, 253,472 women without a hysterectomy or previous cancer diagnosis were included. Follow-up was between 1995 and 2002. Frequency of Pap smear testing was determined by searching the National Health Examination Database. Using the Korean Central Cancer Registry, 248 cases of invasive cervical cancer and 346 cases of carcinoma in situ (CIS) of the cervix were identified. Subjects screened 2 or more times showed a 71% (corrected reduction 60%) and a 66% (corrected reduction 53%) reduced risk of invasive cervical cancer and CIS of the cervix, respectively, as compared with unscreened subjects [relative risk (RR) = 0.29; 95% confidence interval (CI) = 0.20-0.45; RR = 0.34; 95% CI = 0.25-0.46, respectively]. Women with a normal or benign pap smear had a statistically significantly lower risk of invasive cervical cancer and CIS of cervix compared with those never screened. In age-stratified analyses, there was a significant reduction in cervical cancer incidence among women aged 30 and over who were screened 2 or more times compared with women never screened. The results of this prospective cohort study show that regular screening of cervical cancer reduces invasive cervical cancer incidence and CIS of the cervix among Korean women.

Cervical HPV infection and neoplasia in a large population-based prospective study: the Manchester cohort

Cytology and histology records and cervical samples for HPV assay were obtained from a prospective cohort of 49 655 women attending clinics for routine cervical cytology in or near Manchester between 1988 and 1993. The women were followed up for cytological abnormality and neoplasia through the cytology laboratory's records. HPV at entry was assayed in an age- and period-stratified random sample of 7278 women and in prevalent and incident CIN3 cases. The prevalence of newly diagnosed CIN3 increased with time since last normal smear, indicating that most cases persist for several years. CIN3 prevalence did not increase further for screening intervals exceeding 5 years, however, suggesting that CIN3 eventually regresses cytologically. CIN2 prevalence increased less steeply with screening interval, while the prevalence of lesser abnormality was almost independent of screening interval. The prevalence of oncogenic HPV at entry declined from 19% among women aged under 25 to less than 3% at age 40 or above. Oncogenic HPV infection was strongly predictive of subsequent CIN3 (OR 17.2, 95% CI 10.4–28.4), but only weakly related to CIN2 (OR 2.3, 95% CI 0.5–10.7) and lesser abnormality (OR 1.4, 95% CI 0.8–2.5). At current incidence rates, the lifetime risk of developing CIN3 will be 9% in this population. The cumulative risk of CIN3 diagnosis among cytologically normal women with oncogenic HPV detected at entry was 28% (CI 18–43%) after 14 years. Persistence of oncogenic HPV may be more sensitive and specific than cytology for early detection of CIN3 and invasive cancer.

Benefit of cervical screening at different ages: evidence from the UK audit of screening histories

While most experts agree that cervical screening is effective, there remains controversy over the most appropriate screening interval. Annual screening is common in North America. In England, some argue for 3-yearly screening while others believe 5-yearly screening is adequate, and the frequency varies from one part of the country to another. Screening histories of 1305 women aged 20-69 years, diagnosed with frankly invasive cervical cancer and 2532 age-matched controls were obtained from UK screening programme databases. Data were analysed in terms of time since last negative, and time since last screening smear. Five-yearly screening offers considerable protection (83%) against cancer at ages 55-69 years and even annual screening offers only modest additional protection (87%). Three-yearly screening offers additional protection (84%) over 5-yearly screening (73%) for cancers at ages 40-54 years, but is almost as good as annual screening (88%). In women aged 20-39 years, even annual screening is not as effective (76%) as 3-yearly screening in older women, and 3 years after screening cancer rates return to those in unscreened women. This calls into question the policy of having a uniform screening interval from age 20 to 64 years and stresses the value of screening in middle-aged women. British Journal of Cancer (2003) 89, 88-93. doi:10.1038/sj.bjc.6600974 www.bjcancer.com