Evaluation of the Effectiveness of Cervical Cancer Screening: A Case-Control Study in Miyagi, Japan.

Abstract

To estimate the effectiveness of screening for invasive cervical cancer, a case-control study was performed in Miyagi, Japan. A total of 198 cases (129 mass screen-detected and 69 outpatient-detected) of invasive cervical cancer were identified between 1984 and 1990. The results of the Papanicolaou smear of these cases were compared to those of 396 age-(±5 years) and area-matched controls. Compared with women who had no prior screening (cases 51.6%, controls 16.2%), women who were screened had an odds ratio (OR) for invasive cervical cancer of 0.14 (95% confidence interval [CI] 0.088-0.230). The OR for the 175 cases of squamous cell carcinoma was 0.13 (95% CI 0.077-0.215), while the OR for the 23 cases of screened women with adenocarcinoma was 0.40 (95% CI 0.091-1.753). The time intervals following the last negative smear were assessed and we found an OR for a one-year interval and a two-year interval of 0.09 (95% CI 0.055-0.163) and 0.17 (95% CI 0.083-0.335), respectively. In conclusion, screening for invasive cervical cancer is not only effective but also the degree of protection is high for one to two years. cervical cancer; case-control study; cervical cancer screening Miyagi is one of the first areas in Japan to be involved in mass screening for cervical cancer. From 1984From -1990, in Miyagi, a total of one million Papanicolaou (Pap) smears were taken among women over the age of 30. The cytodiagnoses of the Pap smears for these women were performed primarily at the Center for Clinical Cytology (Miyagi Cancer Society). The results of the screening program and the relationship between histological features and history of prior cervical screening have previously been reported by our group (Yajima et al. 1979;. However, the effectiveness of this form of screening for cervical cancer in Miyagi using epidemiological methods has not been described before except for a prelimi-

Stage at Diagnosis and Mortality in Patients with Adenocarcinoma and Adenosquamous Carcinoma of the Uterine Cervix Diagnosed as a Consequence of Cytologic Screening

“…[7][8][9][10][11][12] Case-control studies to date, though statistically underpowered, have suggested that some protection may be conferred, albeit of smaller magnitude than that offered for squamous malignancies. [17][18][19] This result is at odds with the epidemiologic trend and suggests that if an effect is present, it is likely to be small.…”

Recommendations on screening for cervical cancer

“…6,27 The effect of screening on incidence of invasive cervical cancer is shown in Appendix 5 (available at www .cmaj .ca/lookup /suppl /doi :10.1503 /cmaj.121505 / -/DC1). A meta-analysis of 12 case-control studies [28][29][30][31][32][33][34][35][36][37][38][39] showed that the odds of having undergone at least 1 Pap test were lower among women with invasive cervical cancer (OR 0.4, 95% CI 0.3-0.4, Appendix 5) than among women who did not have cervical cancer. A cohort study with a 3-year follow-up found that screening was associated with a decrease in incidence of cervical cancer (relative risk 0.4, 95% CI 0.2-0.6), 38 whereas a randomized controlled trial (RCT) from rural India found a nonsignificant effect of screening on incidence.…”

Effectiveness of Cervical Cancer Screening Based on a Mathematical Screening Model using data from the Hiroshima Prefecture Cancer Registry

“…Results of a case-control study conducted in Japan revealed that between individuals screened annually and biennially, there was a significant decrease in the rate of early detection in those who underwent biennial screenings (Morimura and Ito, 2005). Moreover, a 2-year prevention may be anticipated from a negative biennial cytodiagnostic result; thus, annual screenings are likely much more effective (Makino et al, 1995;Sato et al, 1997). Therefore, an investigation into restoring annual screening is warranted.…”