Oral contraceptives and cervical carcinoma

Pharmacodynamics of combined estrogen-progestin oral contraceptives: 4. Effects on uterine and cervical epithelia

Introduction: Steroid hormones are responsible for specific changes in the endometrium during the menstrual cycle, when they are sequentially secreted and, because of this, in the early days sequential combined oral contraceptive regimens were utilized. The same basic concept has been utilized with multi-phasic regimens, in order to produce endometrial pictures mimicking the normal cycle.Areas covered: The Endometrial effects of progestins and estrogens; combined monophasic high- (50 μg), medium- (30 μg), low- (20 μg), ultralow- (15 μg) estrogen content; sequential regimens; multiphasic combinations; treatment schedules.Cervical effects of combined high-dose and sequential combinations, including evidence for an increase in malignant lesions.Expert opinion: Overall, combined oral contraceptives (COCs) inhibit normal proliferative changes and the endometrium becomes thin, narrow, with widely spaced glands and pre-decidual changes in the stroma. During the first few cycles the progestin induces a coexistence of proliferative and secretory features; with time, the picture changes because the progestin induces a down-regulation of estrogen receptors, resulting in tortuous glands similar to those in the secretory phase, but characterized by a quiescent, atrophic glandular epithelium.In the cervical epithelium, under the influence of high-dose COCs, endocervical glands became hypersecretory and in some instances, distinctive type of atypical polypoid endocervical hyperplasia is found.

Oral Contraceptives and Cervical Neoplasia: Pooled Information from Retrospective and Prospective Epidemiologic Studies

A positive association between the use of oral contraceptives and the risk of cervical neoplasia has been suggested by different sources. This paper examines epidemiologic evidence on this issue through pooled computation of relative risks emerging from 21 studies, subdivided into three main categories: studies based on routine cytologic screening programs, case-control investigations and prospective studies. The pooled estimates of the relative risks for ever vs never use of oral contraceptives were broadly similar and slightly above unity (1.4 from cytologic screening programs, 1.1 from case-control and 1.4 from prospective studies). The risk increased with duration of use and, generally, lower relative risk estimates derived from the older studies, necessarily based on short-term use of oral contraceptives. A particularly limited increase in risk was apparent from case-control investigations. Furthermore, when allowance was made for the major covariates (mostly indicators of sexual habits), a noticeable decrease in the excess risk was evident. In conclusion, although statistical significance of moderate differences in risk can be obtained by pooling data from several studies, a risk of the magnitude of that for the association between oral contraceptives and cervical neoplasia may well be due to bias and confounding. In addition, since sexual behavior only indicates the probability of having been exposed to some sexually transmitted agent (most likely human papilloma virus), the greatest additional contribution may come from a case-control study in which adjustment for such exposure is possible.

Cervical carcinoma and sexual behavior: collaborative reanalysis of individual data on 15,461 women with cervical carcinoma and 29,164 women without cervical carcinoma from 21 epidemiological studies

High-risk human papillomavirus (HPV) types cause most cervical carcinomas and are sexually transmitted. Sexual behavior therefore affects HPV exposure and its cancer sequelae. The International Collaboration of Epidemiological Studies of Cervical Cancer has combined data on lifetime number of sexual partners and age at first sexual intercourse from 21 studies, or groups of studies, including 10,773 women with invasive cervical carcinoma, 4,688 women with cervical intraepithelial neoplasia grade 3 (CIN3)/carcinoma in situ, and 29,164 women without cervical carcinoma. Relative risks for invasive cancer and CIN3 were estimated by conditional logistic regression. Risk of invasive cervical carcinoma increased with lifetime number of sexual partners (P for linear trend <0.001). The relative risk for > or =6 versus 1 partner, conditioned on age, study, and age at first intercourse, was 2.27 [95% confidence interval (95% CI), 1.98-2.61] and increased to 2.78 (95% CI, 2.22-3.47) after additional conditioning on reproductive factors. The risk of invasive cervical carcinoma increased with earlier age at first intercourse (P for linear trend <0.001). The relative risk for age at first intercourse < or =14 versus > or =25 years, conditioned on age, study, and lifetime number of sexual partners was 3.52 (95% CI, 3.04-4.08), which decreased to 2.05 (95% CI, 1.54-2.73) after additional conditioning on reproductive factors. CIN3/carcinoma in situ showed a similar association with lifetime number of sexual partners; however, the association with age at first intercourse was weaker than for invasive carcinoma. Results should be interpreted with caution given the strong correlation between sexual and reproductive factors and the limited information on HPV status.

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

BACKGROUND

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.

Cervical carcinoma and reproductive factors: Collaborative reanalysis of individual data on 16,563 women with cervical carcinoma and 33,542 women without cervical carcinoma from 25 epidemiological studies

The International Collaboration of Epidemiological Studies of Cervical Cancer has combined individual data on 11,161 women with invasive carcinoma, 5,402 women with cervical intraepithelial neoplasia (CIN)3/carcinoma in situ and 33,542 women without cervical carcinoma from 25 epidemiological studies. Relative risks (RRs) and 95% confidence intervals (CIs) of cervical carcinoma in relation to number of full-term pregnancies, and age at first full-term pregnancy, were calculated conditioning by study, age, lifetime number of sexual partners and age at first sexual intercourse. Number of full-term pregnancies was associated with a risk of invasive cervical carcinoma. After controlling for age at first full-term pregnancy, the RR for invasive cervical carcinoma among parous women was 1.76 (95% CI: 1.53-2.02) for > or => or =7 full-term pregnancies compared with 1-2. For CIN3/carcinoma in situ, no significant trend was found with increasing number of births after controlling for age at first full-term pregnancy among parous women. Early age at first full-term pregnancy was also associated with risk of both invasive cervical carcinoma and CIN3/carcinoma in situ. After controlling for number of full-term pregnancies, the RR for first full-term pregnancy at age <17 years compared with > or => or =25 years was 1.77 (95% CI: 1.42-2.23) for invasive cervical carcinoma, and 1.78 (95% CI: 1.26-2.51) for CIN3/carcinoma in situ. Results were similar in analyses restricted to high-risk human papilloma virus (HPV)-positive cases and controls. No relationship was found between cervical HPV positivity and number of full-term pregnancies, or age at first full-term pregnancy among controls. Differences in reproductive habits may have contributed to differences in cervical cancer incidence between developed and developing countries.

Prevalence of high-risk human papillomavirus (HR-HPV) types 16 and 18 in healthy women with cytologically negative Pap smear

OBJECTIVE

To study the prevalence of high-risk human papillomavirus (HR-HPV) types 16 and 18 in healthy women with negative Pap smears in identifying women with underlying cervical squamous intra-epithelial (SIL) lesions.

METHODS

A total of 3300 women who were attending the Gynecology OPD of Lok Nayak Hospital, one of the major government tertiary hospitals in New Delhi, were screened during a 1-year study period, and 2079 (63%) of them were found to have cytologically negative Pap smear with inflammation and the rest (37%) also had negative Pap report but without inflammation. Hundred and sixty of these sexually active women aged between 20 and 60 years were randomly selected, and were investigated by colposcopy and a guided biopsy was done wherever required. HPV types 16 and 18 DNA was detected in scraped cervical cells from all women using type-specific primers in polymerase chain reaction (PCR).

RESULTS

The high-risk HPV (type 16 and 18) prevalence by PCR was found to be 10% (16/160). Histopathological findings were obtained in 123 women, out of which 15 had LSIL and four had HSIL. High-risk HPV types 16/18 could be detected in nine out of these 19 (47.3%) squamous intra-epithelial lesions (p < 0.00008) which includes two out of the four women (50%) having HSIL, while only seven out of 104 (6.7%) of the subjects with normal (negative) Pap reports (p = 0.03) had infection of high-risk HPV.

CONCLUSION

The results indicate that about 10% of women who show a negative Pap smear, but have inflammation are positive for high-risk HPV types 16/18 and about 15% harbor squamous intra-epithelial lesions. It is suggested that high-risk HPV detection can be utilized as an adjunct to routine cytology screening programs to identify 'high risk' women who have concurrently negative Pap smears but may harbor oncogenic HPV infection and/or more likely to develop CIN lesions.

The interaction between steroid hormones, human papillomavirus type 16, E6 oncogene expression, and cervical cancer

Various risk factors have been implicated in the causation of cervical cancer including human papillomavirus (HPV), the early genes (E6 and E7 ) of which encode the main transforming proteins. Studies have suggested that steroid hormones may enhance the expression of these genes leading to loss of p53 gene-mediated cell apoptosis. A total of 120 cervical tissue samples were obtained from patients with proven cervical cancer. Patients who used depo-medroxyprogesterone acetate steroid contraception were recruited as part of the steroid arm. Only HPV DNA type 16 samples were used for the study. Controls included three cell lines (CaSki, SiHa, & C33A) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as an internal housekeeping gene. Of 120 patients, there were 111 patients with HPV type 16 identified. Of this number, RNA was present in 63 samples. There were 30 women (30/63) who used steroid contraception. In relation to patients who used contraception, HPV 16 E6 gene expression was present in 79% (n = 23) and 88% (n = 30) of steroid users compared to nonusers, respectively. In total there were 25 patients (40%) with expression of the HPV 16 E6*I gene and 30 patients with expression of the E6*II gene. There were 57% of steroid users (n = 17) who had expression of the E6*I/E6*II gene, compared to 52% (n = 17) of nonusers (P = 0.800). From a molecular level, this study does not confirm the role of injectable progesterones in cervical carcinogenesis.

The role of steroid contraceptive hormones in the pathogenesis of invasive cervical cancer: a review

Invasive cervical cancer remains a leading cause of morbidity and mortality, especially among women in the developing world where screening is either deficient or absent. Of all agents linked to the causation of this disease, high-risk human papillomavirus (HPV) appears to be the strongest factor. However, not all women with HPV develop cervical cancer. Steroid contraception has been postulated to be one mechanism whereby HPV exerts its tumorigenic effect on cervical tissue. Steroids are thought to bind to specific DNA sequences within transcriptional regulatory regions on the HPV DNA to either increase or suppress transcription of various genes. Although some earlier studies were reassuring as no increased incidence of cervical cancer was observed, subsequent research has shown a causative association, especially among long-term users. The role of steroids was further enhanced by the discovery of hormone receptors in cervical tissue. Some earlier studies of oral contraceptive steroids found no increased risk, even after controlling for other risk factors, including smoking and number of partners. However, prospective studies have shown a greater progression of dysplasia to carcinoma-in-situ with more than 6 years of oral steroid contraceptive use. Similar findings were also evident from other work, including the Royal College of General Practitioners Oral Contraception Study. The WHO Collaborative Study of Neoplasia and Steroid Contraceptives showed a relative risk of 1.2 for invasive cancer in users of the long-acting progestational contraceptive, depo-medroxyprogesterone acetate. However, in users of more than 5 years duration, an estimate of 2.4 was reported. The upstream regulatory region (URR) of the HPV type 16 viral genome, mediates transcriptional control of the HPV genome and is thought to contain enhancer elements that are activated by steroid hormones. It has been shown that steroid hormones bind to specific glucorticoid-response elements within HPV-DNA. Experimental evidence has revealed that high-risk type HPV 16 are able to stimulate the development of vaginal and cervical squamous cell carcinomas in transgenic mice exposed to slow-release pellets of 17 beta-estradiol in the presence of human keratin-14 promoter. Squamous cell carcinomas developed in a multi-stage pathway only in transgenic mice and not in nontransgenic mice. The E6 oncoprotein of HPV 16 has been shown to bind to the p53 tumor suppressor gene and stimulate its degradation by a ubiquitin-dependent protease system. Steroid hormones are thought to increase the expression of the E6 and E7 HPV 16 oncogenes, which in turn bind to and degrade the p53 gene product, leading to apoptotic failure and carcinogenesis. However, the molecular basis of this remains to be proven.

Risk factors for pre-cancerous lesions of the cervix

Studies on risk factors for pre-cancerous lesions of the uterine cervix have shown strong association with sexual practice. Women with multiple sexual partners and intercourse at early age are at high risk. A role of male partners in further enhancing the risk has been identified. All these support the hypothesis relating to a sexually transmissible aetiological agent. An extensive review of the literature on the risk factors for pre-cancerous lesions of cervix has been carried out. The risk factors were grouped into genital, sexual, chemical, dietary and life factors. Human papilloma virus (HPV) is the major infectious aetiological agent associated with the development of pre-cancerous lesions of cervix. Other co-factors such as multiple sexual partners of the male as well as the female and early age of first intercourse are also involved at the critical aetiological step of progression from low-grade to high-grade lesions. The role of other infectious agents in terms of supportive or interactive effects is not clear. No independent effect for herpes simplex virus 2 on risk is observed. Other risk factors include cigarette smoking, oral contraceptive usage, certain nutritional deficiencies and poor personal hygiene. However, it is not clear whether these factors operate independently from HPV. There is no consistency in the independent effect of these factors on the development of low- to high-grade lesions of cervix. There is a similarity in the patterns of risk between pre-cancerous lesions of the cervix and cervical cancer. Monogamy, late commencement of sexual activity, personal hygiene and use of barrier contraceptive methods help towards primary prevention. In the long-term, primary prevention of cervical neoplasia through HPV immunization of population may be a possibility.

The epidemiology of cervical carcinogenesis

Epidemiologic and laboratory data suggest that cervical cancer typically arises from a series of causal steps. Each step can be studied separately in the hope of better etiologic understanding and improved cancer prevention. The earliest identified etiologic step is infection of young women with specific types of venereally transmissible human papillomaviruses (HPVs). Cervical HPV infections often lead to low grade squamous intraepithelial lesions (mildly abnormal Pap smears). Human papillomavirus infections and their associated lesions are extremely common among young, sexually active women. The infections typically resolve spontaneously even at the molecular level within months to a few years. Uncommonly, HPV infections and/or low grade lesions persist and progress to high grade lesions. The risk factors for progression are mainly unknown but include HPV type and intensity, cell-mediated immunity, and reproductive factors. Nutritional factors or co-infection with other pathogens may also be involved at this apparently critical etiologic step between common low grade and uncommon high grade intraepithelial lesions. Except for advancing age, no epidemiologic risk factors have been found for the next step between high grade intraepithelial lesions and invasive cancer. At the molecular level, invasion is associated with integration of viral DNA. Based on worldwide research, the steps in cervical carcinogenesis appear to be fundamentally the same everywhere, with a central role for HPV infection. The importance of etiologic cofactors like smoking, however, may vary by region.

Primary prevention of gynecologic cancers

A shift from treatment to prevention of the three major gynecologic cancers is overdue. The traditional approach to cervical, endometrial, and ovarian cancers has been secondary or tertiary prevention--early detection and treatment or mitigation of damage, respectively. We reviewed the literature on these cancers to identify strategies for primary prevention. Cervical cancer behaves as a sexually transmitted disease. As with other such diseases, barrier and spermicidal contraceptives lower the risk of cervical cancer; the risk reduction approximates 50%. Combination oral contraceptives help prevent both endometrial and epithelial ovarian cancers. The risk of endometrial cancer among former oral contraceptive users is reduced by about 50% and that of ovarian cancer by about 30% to 60%. Weight control confers strong protection against endometrial cancer. Breast-feeding and tubal sterilization also appear to protect against ovarian cancer. Although women have a range of practical, effective measures available to reduce their risk of these cancers, few are aware of them. Without this information, women cannot make fully informed decisions about their health.

Invasive squamous-cell cervical carcinoma and combined oral contraceptives: results from a multinational study. WHO Collaborative Study of Neoplasia and Steroid Contraceptives

Data from a hospital-based case-control study collected in 11 participating centers in 9 countries were analyzed to determine whether use of combined oral contraceptives alters risk of invasive squamous-cell cervical cancer. Information on prior use of oral contraceptives, screening for cervical cancer, and suspected risk factors for this disease were ascertained from interviews of 2361 cases and 13,644 controls. A history of smoking and anal and genital warts was obtained, and blood specimens were collected for measurement of antibodies against herpes simplex and cytomegaloviruses, from selected sub-sets of these women, as was a sexual history from interviews of husbands. The relative risk of invasive squamous-cell cervical carcinoma was estimated to be 1.31, with a 95% confidence interval that excluded one, in women who ever used combined oral contraceptives. Risk of this disease increased significantly with duration of use after 4 to 5 years from first exposure, and declined with the passage of time after cessation of use to that of non-users in about 8 years. No sources of bias or confounding were identified that offered plausible explanations for these findings. The strength of these results, and their consistency with those from other studies, suggest that a causal relationship may exist between use of combined oral contraceptives and squamous-cell cervical carcinoma. Women who have used these products for 4 or more years, and who most recently used them within the past 8 years, should receive high priority for cervical cytologic screening.

Modulatory influence of oral contraceptive pills Ovral and Noracycline on 3-methylcholanthrene-induced carcinogenesis in the uterine cervix of mouse

The present study reports the modulatory influences of combined oral contraceptive formulations, Ovral (0.05 mg ethinylestradiol plus 0.5 mg norgestrel per pill) and Noracycline (0.05 mg ethinylestradiol plus 0.1 mg lynestrenol per pill), on methylcholanthrene (MCA)-induced carcinogenesis in the uterine cervix of Swiss albino mouse. Placement of cotton thread impregnated with beeswax containing approximately 300 micrograms of MCA yielded cervical tumors in 0.0%, 8.6% and 26% animals, respectively, in 30, 60 and 90 days. Concomitant treatments with doses D1 (1/2000th of a pill), D2 (1/200th of a pill) and D3 (1/20th of a pill) of Ovral yielded cervical tumors in 0.0%, 0.0% and 4.5% mice at 30 days, 0.0%, 6.2% and 10% mice at 60 days and in 3.3% (P less than 0.05), 3.4% (P less than 0.05) and 47% mice at 90 days, respectively. Likewise, concomitant treatments with doses D1 (1/2000th of a pill), D2 (1/200th of a pill) and D3 (1/20th of a pill) of Noracycline yielded cervical tumors in 0.0%, 0.0%, 16.6% mice at 30 days, 4%, 3.7% and 54% (P less than 0.05) mice at 60 days and 3.2% (P less than 0.05), 20% and 63% (P less than 0.05) of mice at 90 days, respectively. Both Ovral and Noracycline displayed biphasic action on MCA-induced cervical carcinogenesis in mice. At lower dose levels (D1 and D2), they were inhibitory while at the higher dose level (D3) they were augmentatory in their actions. Both pills also significantly enhanced the incidence of cervical hyperplasia.

Oral contraceptives and cervical neoplasia

Although initial studies examining the relationship of oral contraceptives to risk of cervical neoplasia were reassuring, more recent studies provide some evidence of a positive relationship, particularly for long-term usage. Results, however, are difficult to interpret, because of a variety of methodologic complexities, including potential sources of confounding and bias. Sexual behavior and Pap smear screening have been identified as important confounders, but in several well-controlled studies residual excess risks of nearly 2-fold persist for users of 5 or more years. A possible promotional effect of oral contraceptives is suggested by higher risks associated with recent usage. There also is some suggestion of a stronger effect for adenocarcinomas than for squamous cell tumors. A relationship is biologically possible, given findings of hormone receptors in cervical tissue and the fact that oral contraceptives have been found to induce cervical hyperplasia. In addition, oral contraceptives may induce proliferation of the human papillomaviruses, the leading suspect agent for cervical cancer. Although a number of lines of evidence support a relationship of oral contraceptives to cervical cancer risk, firm conclusions await the results of additional studies that specifically address some of the methodologic shortcomings of previous investigations. In particular, additional follow-up studies are needed to define the effect of oral contraceptives on the natural history of cervical lesions.

Barrier methods of contraception and the risk of cervical neoplasia

The relationship between the use of barrier contraception methods and the risk of cervical neoplasia was analyzed using data from a case-control study conducted in the greater Milan area, northern Italy. A total of 367 cases of invasive cancer under 60 years of age were compared with 323 subjects in hospital for acute conditions unrelated to any of the established or suspected risk factors for cervical cancer, and 316 cases of cervical intraepithelial neoplasia were compared with 258 outpatient controls. Ever-use of barrier methods (condom and diaphragm) was reported by 6% of the cases of invasive cancer and 12% of hospital controls. Corresponding values for intraepithelial neoplasia were 16% for cases and 22% for outpatient controls. Considering the total use of barrier methods, compared to never use, the relative risk of invasive cervical cancer was 0.4 (95% confidence interval 0.2-0.9) and decreased with duration of use (chi 2(1), trend = 5.18, p = 0.02). Likewise, use of barrier methods lowered the risk of intraepithelial neoplasia; the estimated relative risks were 0.9 in users for less than two years and 0.6 for two or more (chi 2(1), trend = 4.61, p = 0.03). Although the protection for invasive cancer appeared to be greater at older ages and in multiparous women, the relative risks were not significantly heterogeneous in various strata of parity, number of sexual partners, oral contraceptive use and history of Pap smears.

Is it safe to prescribe hormonal contraception and replacement therapy to patients with premalignant and malignant uterine cervices?

The levels of estrogen and progesterone receptors in normal and abnormal uterine cervices were determined. The study group consisted of 14 patients with cervical intraepithelial neoplasia (CIN III) and 7 patients with invasive carcinoma of the cervix (stage IB-IIA). The control group included 23 patients who underwent total abdominal hysterectomy for menorrhagia, leiomyoma, etc. The concentration of total estrogen receptors in premalignant and malignant cervices did not differ from the patients with benign conditions of the cervix. The concentration of progesterone receptors was significantly higher in the nonaffected cervices than in the patients with preinvasive and invasive carcinoma of the cervix (P less than 0.05). We have shown that estrogen receptor concentrations do not differ between women with normal and abnormal uterine cervices. Therefore, we feel that the contraceptive pill is not contraindicated in women who have been treated for CIN III. We also maintain that hormone replacement therapy should be given, when indicated, to women who have been castrated following surgery and/or radiotherapy for invasive carcinoma of the cervix.

Cancer of the breast and reproductive tract in relation to use of oral contraceptives

Effects of oral contraception on cancers of the female breast and reproductive tract are critically reviewed from human studies reported since 1980. The cumulative risk of breast cancer through 59 years of age appears to bear no relationship to oral contraceptive (OC) use whatsoever. Studies restricted to women under age 45, however, raise concern about a possible adverse effect from OC use before a first-term pregnancy. A duration-related protective effect against endometrial cancer occurs from use of combined OCs. The risk is reduced by about 40% with 2 years of use, and by about 60% with 4 or more years of oral contraception. Oral contraception in excess of 3 years protects against ovarian cancer. Four years of use confers a 50% reduction in risk and 7 or more years of use confers a 60%-80% reduction in ovarian cancer risk. Studies of cervical dysplasia and carcinoma in situ suggest elevated risks with 2 or more years of OC use, although results are difficult to interpret in view of numerous factors that might distort the findings. The risk of invasive cervical cancer appear to be unaffected by up to 5 years of oral contraception. Beyond this, there is evidence suggesting an elevated risk which approaches a 2-fold increase at 10 years of use. Cancers of the vagina and fallopian tube are extremely rare. Their risks have yet to be characterized in relation to oral contraception.

The effectiveness of cervical screening: a population-based case-control study

The cervical smear histories of 36 women with invasive cervical cancer were compared to those of 120 age-matched controls, drawn from local registrar's offices. Of the cases 47% were screened at least once, while for the controls this figure was 68%. The relative risk of getting invasive cervical cancer for women screened at least once compared to women who were never screened was 0.32. The most important confounding factor was age at first intercourse. Contrary to other studies however, it was found that women who were younger when having first intercourse were screened more often. After correcting the relative risk of screened vs unscreened for age at first intercourse, the relative risk became 0.22. When the length of the interval since the last smear was considered, the relative risk was 0.18 when the smear was made between 2 and 5 years earlier and 0.30 when this smear was made more than 5 years earlier. These results support the assumption that screening is effective in the prevention of invasive cancer of the uterine cervix. Even a screening interval of more than 5 years provides considerable protection.

Prognostic features and treatment of endocervical adenocarcinoma of the cervix

Adenocarcinoma of the cervix represents an increasing percentage of cervical cancers as well as a controversial clinical problem. One hundred seventy-two cases of adenocarcinoma were treated at The University of Michigan Medical Center from 1970 to 1984, representing 16.8% of cervical cancers. Of this group 84 patients were diagnosed with endocervical columnar cell type and form the study population for this report. Survival was influenced by stage, grade, and nodal metastases. Age did not influence survival. Survival in stage I disease was not influenced by treatment modality. Radical surgery or radiation therapy provided equal survival and ovarian conservation did not adversely influence survival. Radical surgery can be considered a primary means of therapy in young women and offers the same advantages over radiation therapy as those offered for squamous cell disease.

Use of oral contraceptives and risk of invasive cervical cancer in previously screened women

Within the context of a larger hospital-based case-control study carried out to assess the efficacy of cervical cancer screening, the possible association between oral contraceptives and risk of invasive cervical cancer has been studied as well. Because in the GDR cytological screening is an integral part of the gynaecological basic care, only a few women reported oral contraceptive use but had no Pap-smears in that study. Thus, the analysis was confined to those 129 cases and 275 controls who had at least one screening Pap-smear in their history and were below the age 55. The significantly increased relative risks for users decreased after adjustment for factors of sexual behaviour and interval since last Pap-smear but remained statistically significant or at borderline significance for some categories of usage. This concerns, in particular, long-term use (7+ years) and early onset of use (less than or equal to 24 years) with relative risks of 1.8 and 3.0, respectively.

Workshop on guidelines to the epidemiology of weak associations. Confounding

The magnitude of confounding is examined in nine case studies of two "weak" relationships: between artificial sweeteners and bladder cancer, and between oral contraceptives and cervical dysplasia. Confounding had little or no influence on the results of any published study. The responsible epidemiologist must always consider the possibility of confounding, no less when associations are weak than when they are strong. Identification of potentially confounding variables is an integral part of good epidemiologic practice. Rarely, however, does confounding itself, especially from unidentified sources, live up to its reputation for introducing seriously spurious associations. An investigator is more likely to be led astray by undetected biases than by pure confounding.

Long-term use of oral contraceptives and risk of invasive cervical cancer

To evaluate the relationship between use of oral contraceptives and risk of invasive cervical cancer, a case-control study involving 479 patients and 789 population controls was undertaken in 5 geographic regions of the US. Initially, the relationship was obscured by confounding variables, particularly the interval since last Pap smear. Control for this variable as well as for sexual and sociodemographic factors revealed an RR of 1.5 overall, with long-term users (5 or more years) being at a 2-fold higher risk than non-users. Pill associations prevailed for both adenocarcinomas and squamous-cell tumors, and risks were highest for those using pills containing high estrogen potencies. In addition, there was some evidence that pill associations were most pronounced among women who had never used barrier methods of contraception or who had histories of genital infections, suggesting that oral contraceptives may act as co-carcinogens with transmissible agents. Our findings provide further evidence that long-term use of oral contraceptives may have a carcinogenic effect on cervical epithelium, but emphasize the need for careful evaluation of confounding influences.

Oral contraceptives and cancers of the breast and of the female genital tract. Interim results from a case-control study

We analysed data from a case-control investigation conducted in Milan, Northern Italy, to evaluate the relation between the use of combination oral contraceptives and the risk of cancers of the breast, ovary, endometrium and cervix uteri. For the present analysis, 776 cases of histologically confirmed breast cancer, 406 of epithelial ovarian cancer and 170 of endometrial cancer aged under 60 were compared with a group of 1,282 subjects below age 60 admitted for a spectrum of acute conditions apparently unrelated to oral contraceptive use or to any of the known or potential risk factors for the diseases under study. Likewise, 225 cases of invasive cervical cancer were compared with 225 age-matched inpatient controls, and 202 cases of cervical intra-epithelial neoplasia with 202 outpatient controls identified in the same screening clinics. The age-adjusted relative risk estimates for ever vs. never use of combination oral contraceptives were 1.04 (95% confidence interval (CI) 0.73-1.37) for breast cancer, 0.68 (95% CI = 0.48-0.97) for epithelial ovarian cancer, 0.50 (95% CI = 0.23-1.12) for endometrial cancer, 1.49 (95% CI = 0.88-2.55) for cervical cancer and 0.77 (95% CI = 0.50-1.18) for cervical intra-epithelial neoplasia. The risk of ovarian cancer decreased and that of invasive cervical cancer increased with longer duration of use. Neither duration of oral contraceptive use nor time since first or last use significantly altered a user's risk of other neoplasms considered. Likewise, analysis of sub-groups of age, parity or other potentially important covariates did not show any important interaction, and allowance for them by means of logistic regression did not materially modify any of the results. These data confirm that combination oral contraceptives confer some protection against ovarian and endometrial cancers but may increase the risk of invasive cervical cancer if used for several years, and indicate that the past or current pattern of oral contraceptive use in Italy is unlikely materially to affect the risk of breast cancer.

Epidemiology of uterine cervical cancer

The epidemiology of cervical cancer presents a number of unique challenges, mainly with respect to disentangling correlated factors and to elucidating biological mechanisms. The available evidence suggests a complex multifactorial etiology, although the relative contributions of risk factors and their interactions remain obscure. Infectious agents are strongly suspected, but as yet not conclusively identified. It is also unclear whether there are subgroups of women or periods of life that are most susceptible to the action of infectious agents, and the contribution of the "male factor" needs to be defined. Several epidemiologic leads can be pursued through biochemical and molecular techniques. Most promising is the recent evidence linking certain HPV types to cervical abnormalities, including cancer, and newly developed probes can be incorporated into epidemiologic studies to evaluate an array of risk factors. Endocrine and metabolic assays may be helpful in clarifying the role of exogenous and possibly endogenous hormones. The effects of cigarette smoking may be further evaluated by studying constituents of tobacco smoke and their metabolites in cervical mucus. Finally, the relationship of diet to cervical cancer should be assessed by examining the levels of micronutrients, trace minerals, and other nutritional indices in body tissues and fluids, as well as through interview data. An understanding of cervical cancer etiology will require a better identification of risk factors for precursor lesions as well as factors that enhance their progression to invasive cancer. Through studies that focus on disease stage and time-related events, it should be possible to clarify the multi-stage processes involved in cervical carcinogenesis, and those factors that may inhibit as well as promote transition rates. The protective effects of screening programs deserve further attention, and research into dietary factors may lead in time to nutritional intervention. Investigation by cell type should also be pursued to define the epidemiology of the rarely occurring adenocarcinomas and adenosquamous carcinomas of the cervix. Finally, preventive strategies should be targeted to high-risk populations, especially those of the lower socioeconomic classes and with limited access to medical care. The need for a renewed focus on epidemiology and prevention is emphasized by recent increases in exposure to several postulated risk factors, including sexual promiscuity, oral contraceptives, and smoking.(ABSTRACT TRUNCATED AT 400 WORDS)

Invasive cervical cancer and combined oral contraceptives. WHO collaborative study of neoplasia and steroid contraceptives

A multicentre, hospital based case-control study is being conducted under the auspices of the World Health Organisation to determine whether steroid contraceptives alter the risk of gynaecological, breast, and hepatic neoplasms. Preliminary results, largely from developing countries, on the relation between combined oral contraceptives and invasive cervical carcinoma showed a relative risk of 1.19 (95% confidence interval 0.99-1.44) in women who had ever used oral contraceptives. The risk increased with duration of use, giving a relative risk of 1.53 after five years. This finding supports a causal interpretation, but it could also be due to incomplete control for confounding sexual variables and other sources of bias.

Neoplasia of the cervix uteri and contraception: a possible adverse effect of the pill

The incidence of biopsy-proven cervical neoplasia during a 10-year follow-up was determined in 6838 parous women who entered the Oxford-Family Planning Association contraceptive study while using oral contraceptives and 3154 parous women who entered the study while using an intrauterine device (IUD). Risk factors for cervical neoplasia, continuation of attendance at family planning clinics, and frequency of examination by cervical cytology were similar in the two groups. All 13 cases of invasive cancer occurred in women in the oral contraceptive group; 9 had more than 6 years' use of the pill. Both carcinoma-in-situ and dysplasia also occurred more frequently in the oral contraceptive group than in the IUD group, and when the two conditions were considered together there was a trend in incidence with duration of oral contraceptive use. The incidence for all three forms of neoplasia combined rose from 0.9 per 1000 woman-years in those with up to 2 years' pill use to 2.2 per 1000 woman-years in those with more than 8 years' pill use. Amongst IUD users, there was no such trend in incidence with duration of use: the rate fluctuated around 1.0 per 1000 woman-years. The great majority of cases of invasive cancer were detected by means of cervical smears and were treated while the disease was still curable. Long-term users of oral contraceptives should have regular cervical cytological examination.

High-risk factors in gynecologic cancer

Cervical cancer retains its character as a venereal disease associated with infections and multiple sexual partners, but poverty also is important. Precise incidence figures for cervical and endometrial cancer are almost nonexistent because in areas with precise case counts there is rarely accurate knowledge of hysterectomy prevalence. For endometrial cancer little recent attention has been paid to any risk factor except exogenous estrogen. It is now suggested that a low pregnancy rate is a cause, not a consequence, of ovarian pathology leading to cancer. Some progress has been made in separating the epidemiologies of various kinds of ovarian and uterine cancer. A few clues are available regarding the epidemiology of fallopian tube cancers and vaginal cancers other than those produced by maternal stilbestrol. Vulvar cancer becomes common only after the age of 75 and so has been neglected epidemiologically.

Drug-induced cancer

This report reviews the medicinal agents that have been linked to human cancer, with emphasis on recent evidence implicating estrogenic compounds such as DES, menopausal estrogens, and oral contraceptives. Attention is also given to drugs that have fallen under suspicion and requires further epidemiologic evaluation. The detection of drug-cancer associations not only influences clinical and public health practice, but may also provide insights into mechanisms of carcinogenesis. The clinician contributes to the prevention of drug-induced cancer by being alert to iatrogenic hazards and cooperating in epidemiologic investigations, by weighing risks versus benefits in individual cases, and by discussing with patients the rationale and risks of proposed forms of therapy.

Oral contraceptive use, sexual activity, and cervical carcinoma

Recent studies suggest that long-term oral contraceptive (OC) use may be related to the development of subsequent cervical carcinoma (CaCx). However, the possible confounding effects of sexual activity on this relationship have not been adequately investigated. In this study of 69 patients with CaCx and 216 matched control subjects, data on sexual activity, as well as OC use, were obtained. Sexual activity and OC usage were seen to be positively related, as were sexual activity and risk of CaCx. These two factors were seen to interact to make the risk of CaCx highest in those women who have been most sexually active and who have used OCs for 4 to 6 years. However, after adjustment for sexual factors, the increase in risk of CaCx attributable to OC use was no longer of statistical significance.

Characteristics of women with dysplasia or carcinoma in situ of the cervix uteri

To identify risk factors for various cervical abnormalities, 237 women with abnoromal cervical smears and 422 control women were interviewed. Cervical biopsy specimens taken from the patients with abnormal smears were reviewed according to standard criteria by one pathologist and classified as follows: 65 carcinoma in situ, 81 severe dysplasia, 44 mild dysplasia and 47 normal histology. Factors associated with risk of mild dysplasia, severe dysplasia and carcinoma in situ were similar to those previously identified for invasive carcinoma, and included age at first intercourse, multiple sexual partners and pregnancy outside marriage. Analysis to disentangle correlated factors revealed that number of sexual partners exerted effects independently of age at first intercourse, whereas the reverse was not true. This finding fails to support suggestions that adolescence is a period when the cervix is most vulnerable to the effects of sexual behaviour. Other factors relating to risk of cervical abnormalities were smoking and use of oral contraceptives. It was not possible to show that these relationships were incidental, but further investigation is required to establish whether they are causal.

Evaluation of the carcinogenic effects of estrogens, progestins and oral contraceptives on cervix, uterus and ovary of animals and man

Estrogens do not have the general biological effect of increasing the occurrence of cancer in various species of laboratory animals. The neoplastic effect of estrogens in animals is strain and species dependent. Estrogens may increase the incidence of uterine cervical cancer in some strains of mice, but not in other strains or other animal species. The progestins and oral contraceptives (OC) have not induced cervical cancer in animals and most studies demonstrate that the steroid anovulants do not increase the occurrence of abnormal cervical smears or cervical cancer in women. Estrogens increase the occurrence of endometrial cancer in the rabbit, occasionally in the mouse, but apparently not in other species. Case-control studies in menopausal and postmenopausal women indicate an increased risk of endometrial carcinoma (EC) associated with use of estrogen. However, in other studies estrogen has not been related to EC. Cases of EC have been reported in women using sequential OC but a causal relationship has not been established. Progestins alone may arrest progress or cause regression of EC in women. EC has not been related to use of the combination OC, and it is unlikely that use of these anovulants will lead to the development of endometrial cancer. Estrogens or OC do not induce a carcinogenic response in the ovary. A decrease in ovarian cysts, is observed during the clinical use of OC.

Oral and intrauterine contraception: a 1978 risk assessment

This report reviews the current literature on the various risks associated with the use of oral contraceptives and intrauterine contraceptive devices. Reports on oral contraceptives from large prospective studies are not beginning to supplement the detailed reports resulting from earlier case-control studies. These studies suggest that in Western societies there is an increase in the incidence of a variety of circulatory diseases, with an increased risk of death. With intrauterine contraceptive devices it now has been fairly well documented that there is an increased risk of pelvic inflammatory disease. After reviewing and assessing the risks of both methods in some detail and comparing these risks to the benefits, the resultant conclusion is that the benefits continue to outweigh the risks for both methods, except for older women who choose oral contraceptives and also are heavy smokers.

Neoplasia and dysplasia of the cervix uteri and contraception: a possible protective effect of the diaphragm

Among the 17,032 women included in the Oxford-Family Planning Association contraceptive study, 65 developed biopsy proven cervical neoplasia (including dysplasia) prior to 1 September 1977. The incidence rate in diaphragm users (0.17 per 1000 woman-years of observation) was much lower than the rates in oral contraceptive users or intrauterine device users (0.95 and 0.87 respectively). This difference could not be explained in terms of confounding variables, nor was it attributable to a lower frequency of cervical smearing among diaphragm users within the clinics. Detailed information about age at first intercourse, numbers of sexual partners and the frequency of cervical smearing outside the clinics was obtained from 52 of the women with cervical neoplasia and 139 matched controls. Diaphragm users were less likely to have had coitus at an early age and had had materially fewer sexual partners than users of the other two methods of contraception. After adjusting for the effects of these variables, however, the risk of cervical neoplasia in diaphragm users was still only about one quarter that in the users of the other methods. Patterns of smearing varied little between users of the various contraceptive methods. Smoking emerged as a major "risk factor" for cervical neoplasia in this study. This probably implies that the smoking habit reflects some important aspect of sexual behaviour relevant to the production of the disease that we have been unable to measure.