Cervical cancer and hormonal contraceptives: collaborative reanalysis of individual data for 16,573 women with cervical cancer and 35,509 women without cervical cancer from 24 epidemiological studies
International Collaboration of Epidemiological Studies of Cervical Cancer,Appleby P,Beral V,Berrington de González A,Colin D,Franceschi S,Goodhill A,Green J,Peto J,Plummer M,Sweetland S
Combined oral contraceptives are classified by the International Agency for Research on Cancer as a cause of cervical cancer. As the incidence of cervical cancer increases with age, the public-health implications of this association depend largely on the persistence of effects long after use of oral contraceptives has ceased. Information from 24 studies worldwide is pooled here to investigate the association between cervical carcinoma and pattern of oral contraceptive use.
Methods
Individual data for 16,573 women with cervical cancer and 35,509 without cervical cancer were reanalysed centrally. Relative risks of cervical cancer were estimated by conditional logistic regression, stratifying by study, age, number of sexual partners, age at first intercourse, parity, smoking, and screening.
Findings
Among current users of oral contraceptives the risk of invasive cervical cancer increased with increasing duration of use (relative risk for 5 or more years' use versus never use, 1.90 [95% CI 1.69-2.13]). The risk declined after use ceased, and by 10 or more years had returned to that of never users. A similar pattern of risk was seen both for invasive and in-situ cancer, and in women who tested positive for high-risk human papillomavirus. Relative risk did not vary substantially between women with different characteristics.
Interpretation
The relative risk of cervical cancer is increased in current users of oral contraceptives and declines after use ceases. 10 years' use of oral contraceptives from around age 20 to 30 years is estimated to increase the cumulative incidence of invasive cervical cancer by age 50 from 7.3 to 8.3 per 1000 in less developed countries and from 3.8 to 4.5 per 1000 in more developed countries.
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PMID 17993361 17993361 DOI 10.1016/S0140-6736(07)61684-5 10.1016/S0140-6736(07)61684-5 International Collaboration of Epidemiological Studies of Cervical Cancer et al. 2007, International Collaboration of Epidemiological Studies of Cervical Cancer 2007
Cite this article
International Collaboration of Epidemiological Studies of Cervical Cancer, Appleby, P., Beral, V., Berrington de González, A., Colin, D., Franceschi, S., Goodhill, A., Green, J., Peto, J., Plummer, M., & Sweetland, S. (2007). Cervical cancer and hormonal contraceptives: collaborative reanalysis of individual data for 16,573 women with cervical cancer and 35,509 women without cervical cancer from 24 epidemiological studies. Lancet (London, England), 370(9599), 1609-1621. https://doi.org/10.1016/S0140-6736(07)61684-5
International Collaboration of Epidemiological Studies of Cervical Cancer, Appleby P, Beral V, Berrington de González A, Colin D, Franceschi S, et al. Cervical cancer and hormonal contraceptives: collaborative reanalysis of individual data for 16,573 women with cervical cancer and 35,509 women without cervical cancer from 24 epidemiological studies. Lancet. 2007;370(9599):1609-1621. doi:10.1016/S0140-6736(07)61684-5
International Collaboration of Epidemiological Studies of Cervical Cancer, et al. "Cervical cancer and hormonal contraceptives: collaborative reanalysis of individual data for 16,573 women with cervical cancer and 35,509 women without cervical cancer from 24 epidemiological studies." Lancet (London, England), vol. 370, no. 9599, 2007, pp. 1609-1621.
Asthana S et al., 2020·Eur J Obstet Gynecol Reprod Biol·
Role of Oral Contraceptive (OC) as a risk factor for cervical cancer remained controversial and unclear. To evaluate risk of cervical cancer in OC users and non-users through a comprehensive systematic review. Search Strategy: Literature search conducted in databases from January 1990 till August 2019 using various search terms. Selection Criteria: Primary research studies that evaluated and assessed the association of OC use with cervical cancer with study design of case control or cohort types published in English language. Data Collection and Analysis: PRISMA guided review was done by two independent researchers. Effect size estimated by pooled Odds ratio with 95 % Confidence Interval (CI) in random effect models on OC pill use for the risk of cervical cancer. Review included 19 studies. Overall risk of invasive cancer on OC use was found to be significant with unknown status of HPV OR (95 % CI) as 1.51 (1.35, 1.68) and for unknown HPV as 1.66 (1.24, 2.21). Adenocarcinoma, squamous cell carcinoma and carcinoma in situ had significant association with OR (95 % CI) of 1.77 (1.4, 2.24), 1.29 (1.18, 1.42) and 1.7 (1.18, 2.44) respectively. OC pills use had a definite associated risk for developing cervical cancer specially for Adenocarcinoma and longer duration of OC pills use.
In addition to HPV, high parity and hormonal contraceptives have been associated with cervical cancer (CC). However, most of the evidence comes from retrospective case-control studies. The aim of this study is to prospectively evaluate associations between hormonal factors and risk of developing cervical intraepithelial neoplasia grade 3 (CIN3)/carcinoma in situ (CIS) and invasive cervical cancer (ICC). Methods and findingsWe followed a cohort of 308,036 women recruited in the European Prospective Investigation into Cancer and Nutrition (EPIC) Study. At enrollment, participants completed a questionnaire and provided serum. After a 9-year median follow-up, 261 ICC and 804 CIN3/CIS cases were reported. In a nested case-control study, the sera from 609 cases and 1,218 matched controls were tested for L1 antibodies against HPV types 11,16,18,31,33,35,45,52,58, and antibodies against Chlamydia trachomatis and Human herpesvirus 2. Multivariate analyses were performed to estimate hazard ratios (HR), odds ratios (OR) and corresponding 95% confidence intervals (CI). The cohort analysis showed that number of full-term pregnancies was positively associated with CIN3/CIS risk (p-trend = 0.03). Duration of oral contraceptives use was associated with a significantly increased risk of both CIN3/CIS and ICC (HR = 1.6 and HR = 1.8 respectively for ≥ 15 years versus never use). Ever use of menopausal hormone therapy was associated with a reduced risk of ICC (HR = 0.5, 95%CI: 0.4-0.8). A non-significant reduced risk of ICC with ever use of intrauterine devices (IUD) was found in the nested case-control analysis (OR = 0.6). Analyses restricted to all cases and HPV seropositive controls yielded similar results, revealing a significant inverse association with IUD for combined CIN3/CIS and ICC (OR = 0.7). Even though HPV is the necessary cause of CC, our results suggest that several hormonal factors are risk factors for cervical carcinogenesis. Adherence to current cervical cancer screening guidelines should minimize the increased risk of CC associated with these hormonal risk factors.
To demonstrate the application of causal inference methods to observational data in the obstetrics and gynecology field, particularly causal modeling and semi-parametric estimation. Human immunodeficiency virus (HIV)-positive women are at increased risk for cervical cancer and its treatable precursors. Determining whether potential risk factors such as hormonal contraception are true causes is critical for informing public health strategies as longevity increases among HIV-positive women in developing countries. We developed a causal model of the factors related to combined oral contraceptive (COC) use and cervical intraepithelial neoplasia 2 or greater (CIN2+) and modified the model to fit the observed data, drawn from women in a cervical cancer screening program at HIV clinics in Kenya. Assumptions required for substantiation of a causal relationship were assessed. We estimated the population-level association using semi-parametric g-computation, inverse probability of treatment weighting, and targeted maximum likelihood estimation. We identified 2 plausible causal paths from COC use to CIN2+: via HPV infection and via increased disease progression. Study data enabled estimation of the latter only with strong assumptions of no unmeasured confounding. Of 2,519 women under 50 screened per protocol, 219 (8.7%) were diagnosed with CIN2+. Marginal modeling suggested a 2.9% (95% confidence interval 0.1%, 6.9%) increase in prevalence of CIN2+ if all women under 50 were exposed to COC; the significance of this association was sensitive to method of estimation and exposure misclassification. Use of causal modeling enabled clear representation of the causal relationship of interest and the assumptions required to estimate that relationship from the observed data. Semi-parametric estimation methods provided flexibility and reduced reliance on correct model form. Although selected results suggest an increased prevalence of CIN2+ associated with COC, evidence is insufficient to conclude causality. Priority areas for future studies to better satisfy causal criteria are identified.
The International Agency for Research on Cancer (IARC) Monographs on the carcinogenic risk to humans concluded that combined oral oestrogen–progestogen contraceptives are carcinogenic to humans (IARC, 2007). This evaluation was made on the basis of increased risks for cancer of the breast (among current and recent users only), cervix and liver (in populations that are at low risk for hepatitis B viral infection). There is also convincing evidence in humans that these agents confer a protective effect against cancer of the endometrium and ovary.