A case-control study on cervical cancer and frequency of participation in screening

Abstract

Introduction Since 1971, all women in Germany have been entitled to an annual free Pap smear for cervical cancer screening (CCS), starting at age 20. Despite the existence of an opportunistic program, cervical cancer still occurs at somewhat elevated rates (9.3 cases per 100,000 women, age-standardized rate, European Standard Population) in Germany in comparison to other Western European countries. Few previous studies reported on the association between participation in CCS and cervical cancer. The TeQaZ study is a population-based case-control study investigating the association between participation in CCS, other risk factors and cervical cancer in Germany. Methods Incident cases of cervical cancer (ICD-10 C53), diagnosed between 2012 and 2016 in the German states of Saxony, Rhineland-Palatinate and the neighboring regions of Baden-Wurttemberg, Hesse, North-Rhine Westphalia, Saarland, Brandenburg, Saxony-Anhalt and Thuringia, were recruited. Cases were matched in a 1:3 ratio with randomly selected population-based controls, recruited via population registries based on age (± 2 years of birth date) and region of residence. Via computer-assisted telephone interviews (CATI, Voxco), cases and controls reported their frequency of CCS participation during the past ten years as well as sociodemographic characteristics, such as income, schooling and other risk factors, namely tobacco smoking, body mass index (BMI, calculated from reported weight, height), use of oral contraceptives, history of chlamydia, condyloma and herpes. Univariable and multivariable conditional logistic regression analyses were performed to estimate the association between CCS participation and cervical cancer using the statistical software SAS. Results A total of 218 cases and 654 controls were included in the analysis. Over 60% of cases and controls were aged 20–39 years. In the ten years prior to the interview, 56.7% of cases and 86.0% of controls attended CCS at least every three years. Fifteen cases (6.9%) and one control (0.2%) had never attended CCS in the past ten years. Among cases, squamous cell carcinoma prevailed (78.9%). In the univariable analyses risk factors for cervical cancer were: CCS participation less frequently than every three years (OR 5.39; 95% CI 3.57–8.14), having ever smoked (OR 1.87; 95% CI 1.34–2.61), having a BMI ≥ 30 (OR 1.69; 95% CI 1.11–2.57), having at least four children (OR 6.96; 95% CI 1.71–28.37) and having had more than one sexual partner (OR 3.11; 95% CI 1.78–5.42). Completing secondary education (OR 0.35; 95% CI 0.23–0.51), engaging sporting activity at least once a week (OR 0.50; 95% CI 0.36–0.70) and a net household income of €3000 or more (OR 0.29; 95% CI 0.19–0.45) were shown to be protective. In the adjusted conditional logistic regression, participating in CCS less frequently than every three years (OR 4.94; 95% CI 2.74–8.91), having at least four children (OR 6.96; 955 CI 1.71–28.37), having had more than one sexual partner (OR 3.91; 95% CI 1.86–8.23) and having ever had a herpes infection (OR 4.62; 95% CI 1.16–18.40) were statistically significantly associated with developing cervical cancer. Completing secondary education (OR 0.42; 95% CI 0.24–0.73) and a net monthly household income of € 3000 or more (OR 0.43; 95% CI 0.25–2.75) remained protective factors. Conclusion Although infrequent participation (less than every three years) was strongly associated with cervical cancer, more than half of cases had attended CCS in the three years prior to diagnosis, suggesting that it is necessary to further investigate the quality of cytology and adequate treatment and monitoring of precancerous lesions in Germany.