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

Some Further Consideration on the Role of Oral Contraceptives in Breast Carcinogenesis

Available evidence concerning oral contraceptives and their potential interaction with reproductive history on breast cancer risk Is reviewed. The relative risks in 15 out of 15 studies were above unity among younger women (i.e., below age 35 and perhaps up to 45) for long-term oral contraceptive use, although apparent heterogeneities emerged in the risk estimates. The overall evidence is reassuring in subsequent age groups, whereas the modifying effects or interactions between oral contraceptives, reproductive factors and breast cancer risk are still largely undefined. Thus we suggest that, besides chance and bias, the apparent discrepancies between various studies should be considered within the framework of the complex time- and age-effects of hormone-related risk factors on breast carcinogenesis.

Projections to the end of the Century of Mortality from Major Cancer Sites in Italy

We used an age-period-cohort model with arbitrary constraints on the parameters, fitted to the mortality data for the period 1955-84, to project rates in mortality from all cancers and 11 major cancer sites in Italy for the period 1985-1999. For all neoplasms considered, using estimated age and cohort values, two models were fitted, one based on constant period effects, and one on a linear regression on the logarithm of the six calendar periods. Furthermore, « a priori » defined coefficients based on epidemiologic inferences were given to period values for tobacco-related neoplasms (below unity for males, above unity for females, on the basis of recent trends in tobacco prevalence in the two sexes), for breast and ovarian cancer (in relation to the potentially different effect of oral contraceptives, other female hormones, reproductive factors and treatment on these neoplasms), and for total cancer mortality. This produced a range of potential estimates, which were reasonably similar for neoplasms (such as stomach, intestines, breast, ovary or prostate) for which no major change in slope of the cohort effects was evident, but wider (i.e., between 188 and 264/100,000 males aged 40 to 79 in 1995-99) for lung or other tobacco-related cancers. Although this range of variation is far from negligible, the estimated values indicate that lung cancer among Italian males aged 40 to 79, even under the more optimistic assumption, will probably be higher at the end of the century than in the early 1980′s, and that lung cancer alone will account for 35 to 42% of all cancer deaths in males between 40 and 79 years. Though any prediction has, by definition, inherent difficulties and uncertainties, cancer mortality in the near future will be strongly influenced by age and cohort effects already known, and hence its projections may offer some indication of public health relevance.

Incidence, mortality, and prognostic factors of small cell carcinoma of the cervix

OBJECTIVE

To compare the incidence, mortality, and presentation of small cell carcinoma of the cervix with other histologies.

METHODS

From 1977 to 2003, 290 women with small cell carcinoma of the cervix uteri were identified from the Surveillance, Epidemiology, and End Results database. Also, 27,527 patients with squamous cell carcinoma of the cervix and 5,231 patients with adenocarcinoma of the cervix were identified for comparison. The annual incidence was calculated and examined for trend. Patient and disease characteristics were compared among histologies. Univariable analyses were conducted using the log-rank test. Multivariable analysis was performed using Cox regression.

RESULTS

The mean annual incidence for small cell carcinoma was 0.06 per 100,000 women, compared with 6.6 and 1.2 for squamous cell carcinoma and adenocarcinoma, respectively. There were significant differences at presentation between small cell carcinoma compared with squamous cell carcinoma and adenocarcinoma for race, treatment, International Federation of Gynecology and Obstetrics stage, and lymph node involvement (P<.05). A trend for improved survival was identified for adenocarcinoma (P=.036) and squamous cell carcinoma (P<.001) but not for small cell carcinoma (P=.672). Five-year survival for small cell carcinoma (35.7%) was worse compared with squamous cell carcinoma (60.5%, hazard ratio 0.55; 95% confidence interval (CI) 0.43-0.69) and adenocarcinoma (69.7%, hazard ratio 0.48; 95% CI 0.37-0.61). On multivariable analysis, age, stage, and race were prognostic for survival in women with small cell carcinoma (P<.05).

CONCLUSION

Small cell carcinoma is a rare histology of cervical cancer associated with a worse prognosis and a predilection for nodal and distant metastasis. The decrease in survival was marked in early-stage and node-negative patients. Because of the high rates of nodal involvement even with early-stage disease, multimodality treatment with radiotherapy and chemotherapy should be considered.

LEVEL OF EVIDENCE

II.

Oral contraceptive and IUD use and endometrial cancer: a population-based case-control study in Shanghai, China

Oral contraceptive (OC) and intrauterine device (IUD) use have been shown to be protective factors for endometrial cancer in several epidemiological studies; however, few studies have been conducted in Chinese populations. We evaluated the association between OC and IUD use and endometrial cancer risk in a population-based case-control study among Chinese women in Shanghai, China. The study included 1,204 newly diagnosed endometrial cancer cases and 1,212 age frequency-matched healthy controls. Logistic regression models were used to estimate adjusted odds ratios (OR) and their 95% confidence intervals (95% CI). In our study population, 18.5% cases and 24.9% controls reported having ever used OCs with an OR of 0.75 (95% CI, 0.60-0.93), after adjusting for known risk or protective factors for endometrial cancer. The risk of endometrial cancer decreased with long-term use of OCs with the OR for more than 72 months of use being 0.50 (95% CI, 0.30-0.85). The effect of OC use remained 25 or more years after cessation of use; the associated OR was 0.57 (95% CI = 0.42-0.78) as compared to nonusers. Similarly, fewer cases than controls had ever used IUD, with the multivariable adjusted OR being 0.53 (95% CI = 0.43-0.65). A reduction in risk was observed regardless the duration of use or age at first and last use. These results suggest that OC and IUD use may confer long-term protection against endometrial cancer.

Ovarian cancer and high-risk women—implications for prevention, screening, and early detection

OBJECTIVE

The aim of this study was to understand the strengths and limitations of current prevention, detection, and screening methods for ovarian cancer and to identify research areas to improve prevention, screening, and detection of the disease for all women as well as for women carrying a mutation in the BRCA1/2 genes.

METHODS

We convened an ovarian cancer symposium at the University of Pittsburgh in May 2002. Nineteen leading scientists representing disciplines such as epidemiology, molecular biology, pathology, genetics, bioinformatics, and psychology presented the latest data on ovarian cancer prevention, screening, and early detection.

RESULTS

Ovarian cancer is the most common cause of death from a gynecologic malignancy in the United States. Because survival depends on stage of diagnosis, early detection is critical in improving clinical outcome. However, existing screening techniques (CA125, transvaginal ultrasound) have not been shown to reduce morbidity or mortality. Moreover, with the exception of oral contraceptives, there are no available chemopreventive agents. Bilateral salpingo-oophorectomy also has been shown to reduce incidence, but this procedure has several drawbacks in terms of a woman's reproductive, cardiovascular, skeletal, and mental health.

CONCLUSIONS

Better methods to prevent, detect, and screen for ovarian cancer in all women, but particularly in high-risk women carrying mutations in BRCA1/2, are urgently needed. This article reviews the current state of knowledge in the etiology, prevention, and early detection of ovarian cancer and suggests several areas for future clinical, epidemiologic, and laboratory-based research.

Hormonal and barrier methods of contraception, oncogenic human papillomaviruses, and cervical squamous intraepithelial lesion development

We assessed the influence of hormonal (oral, injectable, or levonorgestrel [Norplant, Wyeth-Ayerst, Philadelphia, PA]) and barrier methods of contraception on the risk of cervical squamous intraepithelial lesions (SIL), while adjusting for high-risk (HR) HPV infection. Subjects were women receiving family planning services through the state health department clinics from 1995 to 1998. We selected 60 cases with high-grade cervical/SIL (HSIL) and 316 with low-grade cervical/SIL (LSIL) and controls (427 women with normal cervical cytology) and analyzed cervical DNA for HR-HPV, using Hybrid Capture I (Digene; Gaithersburg, MD). When assessing ever use, duration, recency, latency, and age at first use, neither oral contraceptives (OC), Norplant, nor injectable use was associated with an increased risk of SIL development after adjusting for age, age at first sexual intercourse, and HR-HPV positivity. Among HR-HPV-positive women, longer duration barrier method use was associated with a reduced risk of SIL. This finding has important clinical implications for SIL prevention among HR-HPV-infected women.

Height and breast cancer risk

The relationship between adult height and breast cancer risk was considered, combining data from two case-control studies, one conducted between 1983 and 1991 in northern Italy and the other between 1991 and 1994 in six Italian centres. Cases were 5984 women, below the age of 75 years, with histologically confirmed breast cancer, and controls were 5504 women admitted to hospital for a wide spectrum of acute, non-neoplastic, non-hormone-related diseases. No relationship was observed between height and the risk of breast cancer, with a multivariate odds ratio (OR) of 0.96 (95% confidence intervals (CI) 0.85-1.08) for the tallest women (height > or = 166 cm) compared with the shortest (height < 156 cm). No significant heterogeneity was found across strata of age at diagnosis, education, body mass index, body weight, alcohol intake, age at menarche and menopause, parity, age at first birth, ever use of oral contraceptives and hormone replacement therapy, history of benign breast disease and family history of breast cancer. Thus, this study indicates that adult height is not appreciably related to breast cancer risk in this Italian population.

A study of the influence of a gestodene-containing triphasic oral contraceptive on endometrial morphology

The objective of the study was to investigate histological changes in the endometrium in 20 volunteers treated with a low-dose, gestodene-containing triphasic oral contraceptive. Endometrial biopsy specimens were taken before, during a 6-month period of oral contraceptive use and in a post-treatment period. These specimens were evaluated using light microscopy, scanning and transmission electron microscopy. In addition, ultrasound examinations of the uterus, endometrial thickness and ovaries were performed. The low-dose, gestodene-containing triphasic oral contraceptive had no adverse effects on the endometrium (e.g. no proliferation, no polyps, no inflammatory processes), was well tolerated and showed a low side-effect profile. The inhibition of endometrial transformation was demonstrated both by endometrial morphology as well as by endometrial thickness, as measured by transvaginal ultrasound examination.

Family history in ovarian cancer referral population

In order to determine the incidence of familial and hereditary ovarian cancer in a referral patient population, we conducted a retrospective study of 44 patients from a consecutive set of 62 patients treated for ovarian carcinoma at the Gynecologic Oncology Clinic at the Richland Memorial Hospital Center for Cancer Treatment and Research between January 1, 1993 and December 31, 1993. In our study of the referred patients, only two (4.55%) reported a history of at least one first-degree relative also being affected with ovarian cancer. However, 13 patients (29.55%) reported a family history consistent with one of the hereditary ovarian cancer syndromes. In addition to having a suggestive family history, these 13 families demonstrated several cardinal features of hereditary cancer syndromes including early onset, bilaterality, multiple primary tumors, and transmission. Race was the only significantly different demographic factor between the hereditary and sporadic ovarian cancer groups. All 13 patients who appeared to have a hereditary form of cancer were Caucasian.

Etiology of cervical cancer: current concepts

The data on the etiological factors presented here may enable us to suggest a synergism between the various factors associated with the pathogenesis of cervical cancer. Infection of the cervix by HPV 16/18 may result in persistence of viral DNA. The persistent HPV-DNA undergoes disruption at the E2 region, when integrated into the host genome. The transcriptional products E6 and E7 oncoproteins bind to and cause the degradation of p53 and Rb tumor-suppressor gene products. It is possible that, at that point, other cofactors may be involved in the progression toward a precancerous or cancerous condition. Those cofactors may include cigarette smoking, by introducing co-carcinogens to the tissue or by suppressing the local or systemic immune resistance similar to the effect of depressed immune resistance seen in AIDS or immunosuppression of transplant patients; hormones, by enhancing growth of HPV and transformation of HPV infected cells; low serum vitamin levels leading to decreased tissue resistance; or other infections causing local inflammation and the production of free radicals. CIN develops, leading eventually to cervical cancer.

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.

Recency, duration, and progestin content of oral contraceptives in relation to the incidence of endometrial cancer (Washington, USA)

Women who have used combined oral contraceptives (COC) have a reduced risk of endometrial cancer relative to that of women who have never used oral contraceptives, but it is unclear whether the size of the reduction is influenced by the progestin content of the preparation. We analyzed data from two population-based case-control studies of endometrial cancer to investigate this question. Among women aged 40 to 59 years who were residents of King or Pierce Counties, Washington (United States), incident cases who were diagnosed during 1975-77 or 1985-87 were identified. Personal interviews were conducted with 316 such women and their responses compared with those of 501 controls who were selected by household surveys or random-digit dialing. A reduced risk of endometrial cancer associated with COC use was present only among users of five or more years' duration, and even then only in women who were not long-term users of unopposed postmenopausal estrogens. Among these women, the relative risk (RR) of endometrial cancer did not differ according to the progestin potency of the COC used: it was equally low for women who had used a COC with low progestin content (RR = 0.2, 95 percent confidence interval [CI] = 0.1-0.8) as for women who had used a COC with high progestin content (RR = 0.3, CI = 0.1-0.9). Our results argue that, if the reduced risk of endometrial cancer in long-term users of COCs is due to the progestins contained in these preparations, that amount of progestin in most COCs exceeds the threshold amount needed to produce this beneficial effect.

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.

Oral contraceptives and breast cancer in northern Italy. Final report from a case-control study

To assess the relation between oral contraceptive (OC) use and breast cancer, we analysed data from a case-control study conducted in Northern Italy between 1983 and 1991 on 2,309 cases below age 60 and 1,928 controls admitted to hospital for acute diseases unrelated to OC use and to any of the known or potential risk factors for breast cancer. OC use was reported by 16% of cases and 14% of controls. The multivariate relative risk (RR) for ever vs never use of combination OC was 1.2 (95% confidence interval (CI) 1.0-1.4). However, there was no trend in risk with duration. The RR was elevated for very short use, but declined to 0.8 (95% CI = 0.5-1.0) for five or more years' use. No noteworthy relationship was found for other major measures of OC use, although RR estimates were above unity for women who had stopped use less than 5 years before (RR = 1.5, 95% CI = 1.1-2.0), started use less than 10 years before (RR = 1.3, 95% CI = 1.0-1.9), started when 25 or more years old (RR = 1.4, 95% CI = 1.1-1.7), or after first birth (RR = 1.2, 95% CI = 1.0-1.5). No interaction was observed between OC use and family history of breast cancer, parity and age at first birth. A separate analysis of 373 cases and 456 control below age 40 showed no association with ever use (RR = 0.9, 95% CI = 0.6-1.2).

Oral contraceptives and endometrial cancer: do other risk factors modify the association?

The joint effect of use of combination-type oral contraceptives and other exposure factors on risk of endometrial cancer was examined in data from a multicenter case-control study conducted in 5 areas of the United States. Cases were 405 women with histologically confirmed invasive epithelial endometrial cancer first treated at one of 7 participating hospitals. A total of 297 population-based controls of similar age, race, and geographic area were selected as a comparison group. Information on exposure factors was derived from in-person interviews. Combination-type oral contraceptive (COC) use was associated with a significant reduction in risk of endometrial cancer, with an adjusted odds ratio (OR) of 0.4 (95% confidence interval 0.3 to 0.7) for ever compared to never use. Long-term (> or = 10 years) users experienced a markedly lower risk (OR = 0.2). Women who discontinued COC use > or = 20 years earlier remained at reduced risk (OR = 0.7) compared with non-users. The negative association with COC use was apparent regardless of the presence or level of several other risk factors for endometrial cancer, including age, menopausal status, parity, obesity, ever-use of menopausal estrogens, smoking history, or history of infertility. The magnitude of the negative association observed in COC users, however, was considerably diminished in women with no full-term births and in women who subsequently used replacement estrogens for 3 or more years. These results provide new evidence that the protective effect of COC use lasts for 20 or more years after use is discontinued, and highlight several sub-groups of users in whom the level of protection is attenuated by the presence of other risk factors for this disease.

Age-specific differences in the relationship between oral contraceptive use and breast cancer

BACKGROUND

Nearly all studies have suggested that the use of oral contraceptives (OC) is not associated with the aggregate risk of breast cancer diagnosed in women aged 20-54 years. Because of age-specific differences in the breast cancer-parity relationship and because of age-specific differences in other breast cancer risk factors, the Centers for Disease Control reexamined data from the Cancer and Steroid Hormone Study (CASH) to assess whether OC use has different effects on the risk of breast cancer at different ages of diagnosis.

METHODS

This population-based case-control study was designed to examine the relationship between the use of OC and the risk of breast, ovarian, and endometrial cancer. CASH was conducted in eight geographic areas in the United States during 1980-1982. All participants were interviewed at home with a pretested standardized questionnaire including a calendar of life events and a photograph book of all pills marketed in the United States.

RESULTS

We found that the relationship between the risk of breast cancer and OC use appeared to vary by the age at diagnosis. Among women aged 20-34 years at diagnosis or interview, those who had ever used OC had a slightly increased risk of breast cancer (odds ratio [OR], 1.4; 95% confidence interval [CI], 1.0-2.1) compared with women of the same ages who had never used OC. Among these women, there were no trends of increasing or decreasing risk with any measure of OC use. Among women aged 35-44 years, there was no association between OC use and breast cancer. Among women aged 45-54 years, those who used OC had a slightly decreased risk of breast cancer (OR, 0.9; 95% CI, 0.8-1.0). Among these women, risk estimates decreased significantly with increasing time since first and last use.

CONCLUSIONS

Although the slightly increased risk estimates for the youngest women were compatible with findings by other investigators, the decreased risk estimates for the oldest women have not been described in as many studies. Available data provide no reasons to change prescribing practices or the use of OC that are related to the breast cancer risk.

Oral contraceptive use and breast cancer risk: a meta-analysis of variations with age at diagnosis, parity and total duration of oral contraceptive use

OBJECTIVE

To review published reports of risk of breast cancer with oral contraceptive use.

DESIGN

Meta-analysis of study results, using regression techniques to explore the inter-study heterogeneity.

SETTING

Twenty-seven epidemiological studies of breast cancer risk and oral contraceptive use published 1980-1989.

MAIN OUTCOME MEASURES

Relative risk of breast cancer with oral contraceptive use; variations by age at diagnosis, parity, and total duration of use, and with study design characteristics.

RESULTS

The overall relative risk estimate was 1.16 (95% CI 1.07-1.25) for the less than 45 years group, 1.21 (95% CI 0.99-1.47) for the nulliparous subgroup, and 1.27 (95% CI 1.12-1.44) for durations of use of more than 8 years. Source of subjects, their marital status, the type of study, data collection methods, matching for geographical area, the number of adjustment factors used in the study analysis, the country of study and the calendar period in which the study ended were all important explanatory factors for inter-study variation, but a substantial proportion of inter-study variation remained unexplained.

CONCLUSIONS

These meta-analyses suggest that risk of breast cancer may be raised by around 20% in younger, nulliparous and long use duration subgroups of oral contraceptive users. Risk estimates appear to be influenced by several study design factors, which should be considered carefully in designing and reviewing future studies.

High-dose and low-dose combined oral contraceptives: protection against epithelial ovarian cancer and the length of the protective effect. The WHO Collaborative Study of Neoplasia and Steroid Contraceptives

The relations between use of high-dose and low-dose combined oral contraceptives and epithelial ovarian cancer were compared in an international hospital-based case-control study. 393 cases from seven countries were compared with 2561 matched controls. The odds ratio (OR) was somewhat lower for women who used high-dose oestrogen oral contraceptives (OR = 0.68) than for women who used low-dose preparations (OR = 0.81) although the difference could have occurred by chance. After controlling for time since last use, risk was slightly lower for long-term users of high-dose preparations than for long-term users of low-dose pills. Both high-dose and low-dose oral contraceptives protect against ovarian cancer, but the degree of protection may be slightly weaker for the newer, low-dose products.

Cervical cancer and methods of contraception

When evaluating whether the use of a particular method of contraception is associated with an increased or decreased risk of cervical cancer, it is important to be aware of the epidemiological factors which might lead to incorrect conclusions. After careful consideration of the issues, and examination of the available data, it is concluded that women who use oral contraceptives are possibly at increased risk of invasive cervical cancer; users of barrier methods probably have a decreased risk (although the protective effect may differ between the various types of barrier method); and that users of other methods of contraception do not have an altered risk.

Oral contraceptives and breast disease

Epidemiologic data support the hypothesis that the types of OCs used before the mid-1970s protected against most forms of benign breast disease. It is unclear whether current low-dose progestogen OCs will confer the same protection. Further studies are necessary to clarify this. For breast cancer, the relationship is more complex. It is possible that prolonged use of high-dose OCs exert a small increased risk for breast cancer development in women before age 45. Furthermore, prolonged use before a first term pregnancy may result in a small increase in risk for breast cancer before age 45. Studies evaluating the effect of current low-dose OCs are necessary to elucidate what, if any, effect they may have on breast cancer development. Furthermore, as our population ages, studies will be able to determine what effect, if any, may be present in women over age 60, those women with the highest underlying risk of breast cancer. And finally, more research of basic breast tissue physiology and the effect of endogenous and exogenous hormones on this complex organ is needed.

Oral contraceptives and breast cancer: review of the epidemiologic literature

Oral contraceptives have caused little or no overall increase in risk of breast cancer in women in developed countries, even in long-term users or after more than two decades since initial exposure. Limited evidence suggests a possible small increase in risk in users of oral contraceptives in developing countries, and further studies of breast cancer and oral contraceptives in low risk populations are warranted. Oral contraceptives may enhance risk of breast cancer in young women with a history of benign breast disease, and this possibility should also be investigated further. Multiple investigations have fairly consistently shown risk of breast cancer in women under age 45 years to be increased slightly in long-term users of oral contraceptives. Further studies should be conducted to elucidate the mechanism of this apparent phenomenon.

Oral contraceptives and neoplasia of the uterine corpus

Effects of oral contraception on neoplasia of the uterine corpus are reviewed on the basis of epidemiologic studies reported to date. A duration-related protective effect against endometrial cancer occurs from use of combined oral contraceptives, those in which each active pill contains both estrogen and progestogen. The risk before age 60 years is reduced by about 38% with two years of use; use of combined OCs for 4, 8, and 12 years, respectively, confers an estimated 51%, 64%, and 70% reduction in endometrial cancer risk. The protective effect appears not to be diminished by discontinued use, even 15 or more years after stopping. Whether protection continues throughout the entire postmenopausal period, even in the presence of long-term hormone replacement therapy, remains to be seen. Use of combined OCs may protect against uterine leiomyomas ("fibroids"), but the evidence is not conclusive. The few findings about effects of oral contraception on the risk of adenomatous hyperplasia are of uncertain validity. Only one study, with few patients, has considered oral contraception in relation to uterine sarcomas.

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.

Oral contraceptives and neoplasia of the ovary

Epidemiologic literature on oral contraceptives in relation to primary ovarian cancer is reviewed. Compared to women who have never used oral contraceptives, women who have ever taken oral contraceptives have about a 30% reduction in risk for epithelial ovarian cancer, and five or more years of use is associated with a 50% reduction in risk. The protective effect of oral contraceptives persists for ten or more years after use is discontinued, and becomes apparent several years after beginning use. Effects of oral contraceptives are similar for malignant and borderline malignant epithelial ovarian cancer. Reduced risks among oral contraceptive users have been observed for all major histologic subtypes of epithelial ovarian cancer, and for women from developed and developing countries. Risk estimates for epithelial ovarian cancer in relation to oral contraceptive use stratified by age at diagnosis or parity are not uniform across studies. No consistent protective effect is apparent for non-epithelial ovarian tumors or benign ovarian tumors, including teratomas and cystadenomas, although limited data are available on the relationship between oral contraceptives and these neoplasms. Several areas for future research are described.

Combined oral contraceptives containing chlormadinone acetate and breast cancer: results of a case-control study

The main subject of this hospital-based case-control study was the possible relationship between use of combined oral contraceptives (OCs) containing chlormadinone acetate and breast cancer. Analyses were based on data from 490 cases with newly diagnosed breast cancer and 1,223 controls and were separately performed for combined OCs with and without chlormadinone. For either of the combined OCs, risk was not elevated in ever users, did not increase with duration of use and did not change with time since initial exposure or with time since most recent use. However, the relative risk was increased in current users: RR = 1.72 (0.88, 3.36) for combined OCs with chlormadinone and RR = 1.42 (1.01, 2.00) for combined OCs without chlormadinone, which is, however, explained as a screening effect. These results show that chlormadinone as a constituent of combined OCs does not influence breast cancer risk.

The epidemiology of endometrial cancer

The descriptive and analytical epidemiology of endometrial cancer is reviewed. Over the last few decades, age-standardized incidence rates have been rising in several countries. The rise has been even greater in terms of absolute numbers of cases, and hence public health implications, due to the aging of the population. Although endometrial cancer rates were found to be higher in richer countries and urban populations, there is now evidence of some changes in the socioeconomic determinants of the disease in developed countries. In etiological terms, any factor that increases exposure to unopposed estrogens (such as menopausal replacement treatment, obesity, and irregular menstrual cycles) tends to increase the risk of the disease, while factors that decrease exposure to estrogens or increase progesterone levels (such as oral contraceptives or smoking) tend to be protective. Less well defined, or more difficult to explain in biological terms, is the role of other factors, such as births, miscarriages, or diabetes and hypertension, and only suggestive evidence is available on diet from analytical epidemiology. The data reviewed herein are discussed in terms of models of carcinogenesis, as well as attributable risks and public health implications.

Oral contraceptives and the risk of endometrial cancer

The relationship between the use of combination oral contraceptives (OCs) and the risk of endometrial cancer was assessed in a case-control study conducted in the Swiss Canton of Vaud between 1 January 1988 and 31 July 1990. Subjects included 122 women aged 75 or less with histologically confirmed endometrial cancer, and 309 control women in hospital for acute conditions unrelated to OC use. Overall, 14 percent of cases and 27 percent of controls had ever used OCs, corresponding to a multivariate relative risk (RR) of 0.5 (95 percent confidence interval [CI]: 0.3, 0.8). The risk of endometrial cancer was found to be related inversely to duration of OC use: RR = 1.0 for less than two years of OC use; 0.5 for two to five years; and 0.3 (95 percent CI: 0.1, 0.7) for more than five years. The protection appeared greater within 20 years since last use, and the RR rose to 0.8 after 20 or more years since last use; numbers are too small, however, for reliable inference from these subanalyses. No significant interaction or modifying effect was observed with other major factors related to endometrial cancer, including parity, body mass index, estrogen replacement therapy, and cigarette smoking. While this study provides further evidence for the protective effect of OCs against risk of endometrial cancer, the relationship requires continued evaluation to assess the long-term implications and public health impact of OC use.

[Oral contraceptives and breast cancer: analysis of the statistical power of the association]

The power of the association between oral contraceptives and breast cancer was analysed in all the papers published up to date. Seventy-seven publications (from 44 studies) were collected and graded as to quality using meta-analytical methods. Power achieved a figure of greater than or equal to 0.8 in a 10.8% of the associations studied. It showed a significant relationship with the existence of a significant relative risk of the oral contraceptives for breast cancer. The relationship with the sample size of a study was not linear. Power did not show any significant relationship to other variables related to the design of a study (apart from matching, being the power higher in unmatched studies), or to the biases detected, although studies considered as unbiased yielded a higher power. Logistic regression analysis included as predictors of a power greater than or equal to 0.80 the existence of a significant relative risk and the lack of biases in a research.

Oral contraceptives and breast cancer. Review and meta-analysis

To evaluate the relation between use of oral contraceptives and the incidence of breast cancer, the authors reviewed the epidemiologic literature and used quantitative methods to summarize the data. Study results for any use of oral contraceptives were pooled using a model that accounted for both interstudy and intrastudy variability. The authors also explored interstudy variability and modeled a duration-effect relation between oral contraceptive use and breast cancer. Case-control and follow-up studies were considered separately. Overall, the authors observed no increase in the risk of breast cancer for women who had ever used oral contraceptives, even after a long duration of use. These results were consistent across study design. However, data combined from case-control studies revealed a statistically significant positive trend (P = 0.001) in the risk of premenopausal breast cancer for women exposed to oral contraceptives for longer duration. This risk was predominant among women who used oral contraceptives for at least 4 years before their first term pregnancy (relative risk = 1.72; 95% confidence interval = 1.36 to 2.19). Additional study is required to determine whether this finding in a subgroup of exposed women is confirmed and whether the risk remains increased with advancing age.

The relationship between oral contraceptive use, cancer and vascular disease

An overview of the available epidemiological evidence on the connection between oral contraceptives and cancer or vascular disease is presented, including the observation that epidemiological studies have produced important indications for changing both the composition and prescription patterns of oral contraceptives to avoid a large proportion of vascular side effects. Further, the evidence is remarkably clear and consistent in relation to the elevated risks of cervical neoplasms and, although based on a limited number of small studies, of primary liver cancer; protection against endometrial and ovarian cancers up to middle age; and the absence of association with malignant melanoma. There are still uncertainties regarding breast cancer, mainly related to the role of time factors, and the potential persisting risk related to long term use at younger age: published studies, in fact, show elevated risks for long term use in women below age 35 or perhaps up to age 45, but no evidence of association in middle age. Since breast cancer and ovarian cancer account for most of the mortality burden in women up to age 50 or 55 in developed countries, a clarification of the risk relationship for these 2 neoplasms will determine most of the quantitative evaluation on positive or adverse effects of oral contraceptives. The impact of other neoplasms and of cardiovascular disease, on the basis of current oral contraceptive composition, is comparatively limited, if not negligible.

Oral contraceptives and breast cancer

Among women in general the risk of breast cancer through 59 years of age does not appear to be affected appreciably by the use of oral contraceptives. Nonetheless, concern continues to be expressed about the effects of early age at first use, long-term duration of use, formulation, and a variety of other factors thought to influence breast cancer risk in the presence of oral contraception. A number of recent studies restricted to young women suggest that long-term use may increase the risk of disease occurring very early, but the present lack of consistent findings in well-conducted epidemiologic studies prevents any certain conclusion with regard to cause-and-effect. However, if an increased risk were indeed present, the most plausible interpretation is that long-term oral contraception promotes earlier clinical manifestation of breast cancer in some women while having no net impact on their lifetime risk of the disease.

The application of age, period and cohort models to predict Swiss cancer mortality

In order to project trends in mortality from 11 major cancer sites in Switzerland to the end of the current century, a log-linear Poisson age/period/cohort model with arbitrary constraints on the parameters was used, fitted to the observed rates for the period 1950-84. One projection was based on the assumption of a total absence of change in the effect of period, the second was based on a linear extrapolation of the logarithms of the seven known periods, and the third was related to a series of a priori external epidemiological hypotheses, whenever available. For instance, coefficients below unity were used for lung and other tobacco-related neoplasms in men, since some decline in exposure to tobacco carcinogens was observed among Swiss men, and above unity for women since the prevalence of smoking has risen among successive generations of women. Although the method has limitations and uncertainties, several qualitative indications could be derived from this exercise. For instance, the various models suggest that the age-standardized mortality from oral cancer in men will probably increase up to the end of the century, even under the optimistic assumption of an appreciable decline in smoking, while cancer of the oesophagus is likely to level-off around current values, as other tobacco-related neoplasms, prostate cancer in men, and breast cancer in women will probably do. Some steady decline is predicted by various models fitted to the incidence of stomach and intestinal cancer in both sexes, and to ovarian cancer. Lung cancer will continue to rise in women but will stop rising in men, and it will possibly fall if the hypothesis of a decline in exposure to tobacco carcinogens proves correct. Although any prediction has, by definition, substantial difficulties and uncertainties, projections of cancer mortality in the near future are based on a substantial amount of information already available, and may offer valuable information for epidemiological inferences and health planning purposes.

Breast cancer and combined oral contraceptives: results from a multinational study. The WHO Collaborative Study of Neoplasia and Steroid Contraceptives

A collaborative, hospital-based case-control study was conducted at 12 participating centres in 10 countries. Based on data from personal interviews of 2,116 women with newly diagnosed breast cancer and 12,077 controls, the relative risk of breast cancer in women who ever used oral contraceptives was estimated to be 1.15 (1.02, 1.29). Estimated values of this relative risk based on data from three developed and seven developing countries were 1.07 (0.91, 1.26) and 1.24 (1.05, 1.47) respectively; these estimates are not significantly different (P = 0.22). Estimates for women under and over age 35 were 1.26 (0.95, 1.66) and 1.12 (0.98, 1.27), respectively, and these estimates are also not significantly different (P = 0.38). Risk was highest in recent and current users and declined with time since last use regardless of use. Risk did not increase with duration of use after stratifying on time since last use. Risk did not increase significantly with increasing duration of use before age 25 or before a first live birth. However, a relative risk of 1.5 that was of borderline statistical significance was observed in women who used oral contraceptives for more than 2 years before age 25. No single source of bias or confounding was identified that could explain the small increases in risk that were observed. Chance alone is also an unlikely explanation. The results could be due to a combination of chance and potential sources of bias, or they could represent a weak causal relationship.

Oral contraceptives and breast cancer: results from an expanded case-control study

The relationship between oral contraceptives and breast cancer was evaluated among 2,022 cases and 2,183 controls participating in a multicentre breast cancer screening programme. Ever use of oral contraceptives was not related to breast cancer risk (RR = 1.0, 95% CI 0.9-1.2), and no overall patterns of increasing or decreasing risks were observed according to the duration of use, or time since first or most recent use. Although we had no women with extended periods of oral contraceptive use early in life, no evidence of adverse effects attributable to short-term use before age 25, before first live birth or during the perimenopausal period were observed. Further, oral contraceptives did not interact with other breast cancer risk factors, except among those with a history of two or more breast biopsies (RR = 2.0). Analyses by stage of disease revealed that risk was related to the duration of oral contraceptive use: greater than or equal to 5 years use was associated with reduced risk for in situ cancer (RR = 0.59) and increased risks for invasive cancers (RR = 1.5 and 1.4 respectively for small and large lesions). These data suggest that oral contraceptive effects may vary by stage of disease, but provide no overall evidence of an association between oral contraceptives and breast cancer.

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.

A case-control study of cancer of endometrium in Athens

Eighty-three women with invasive adenocarcinoma of the endometrium and 164 control women hospitalized for various orthopedic conditions were interviewed regarding demographic, reproductive, socio-economic and biomedical characteristics, including their use of tobacco, drugs and exogenous estrogens. The data were analyzed by modelling rate ratio (r) through multiple logistic regression. The main results were as follows: women with invasive adenocarcinoma of the endometrium had earlier menarche (r = 0.82 for every additional year; one-tailed p approx. 0.04), later menopause (r = 1.50 for a 5-year difference; one-tailed p approx. 0.004), and fewer live-born children (r = 0.86 for every additional child; one-tailed p approx. 0.08); they were also taller (r = 1.33 for a 5-cm difference; one-tailed p approx 0.03), whereas weight, adjusted for height, was not a statistically significant risk indicator (one-tailed p approx. 0.38). Regular use of combination oral contraceptives was associated with a reduced risk of endometrial cancer (r = 0.56), whereas intake of menopausal estrogens for more than 6 months was associated with an increased risk (r = 2.04); however, because of the low frequency of use of exogenous estrogen preparations in Greece, neither of these 2 results was statistically significant. Tobacco smoking was associated with a significantly reduced risk of endometrial cancer; smoking 15-20 cigarettes per day for 20 years was associated with a rate ratio of 0.49 (one-tailed p approx. 0.03). The protective effect of tobacco smoking was evident only among post-menopausal women. These results indicate that the risk profile of endometrial cancer is similar in high-risk and low-risk countries, and underline the importance of unopposed estrogenic stimulation in the pathogenesis of this cancer.

Risk factors for cancer of the cervix in a rural Chinese population

A population-based case-control study of 109 women with invasive squamous-cell cervical cancer and 545 controls matched for age and area of residence was carried out in Jingan, China, to evaluate the importance of different risk factors and the effect of cervical cancer screening. After controlling for the protective effect of cervical cancer screening, several factors were found to make an independent contribution to risk. These included the number of sexual partners of the subjects and their husbands (OR: 3.9 for 2 or more sexual partners other than the current spouse, relative to none; 5.9 for 2 or more other partners of the husband relative to none), and poor genital hygiene (OR: 4.8 for absence of daily genital washing relative to washing every day; 0.3 for use of sanitary napkin), these are consistent with an infectious etiology. In addition, menstrual characteristics also had a strong relationship to the risk of cervical cancer (OR: 2.2 for 4 or more days' menstruation relative to shorter duration; 5.4 for irregular menstruation).

Reproductive factors and the risk of invasive and intraepithelial cervical neoplasia

The relation between reproductive factors and cervical neoplasia was evaluated in a case-control study of 528 cases of invasive cancer compared with 456 control subjects in hospital for acute conditions unrelated to any of the established or suspected risk factors for cervical cancer, and of 335 cases of cervical intraepithelial neoplasia compared with 262 outpatient controls. The risk of invasive cervical cancer increased with number of livebirths, the estimated multivariate relative risk (RR) being 4.39 in women with five or more births compared with nulliparous women. There was also an inverse relation with age at first livebirth (RR = 0.42 for greater than or equal to 30 vs. less than 20 years) which, however, disappeared after inclusion of parity in multiple logistic regression analysis. Likewise, cases of invasive cervical cancer tended more frequently to report induced abortions. However, this association was not statistically significant after allowance for confounding factors, including parity. No relation emerged with number of spontaneous abortion and age at last pregnancy. When the interaction between parity and sexual habits was analysed, the relative risk increased in subsequent strata of parity with increasing number of sexual partners or decreasing age at first intercourse, thus suggesting an independent effect of sexual and reproductive factors, and hence multiplicative on the relative risk of invasive cervical cancer. No consistent association emerged between the risk of intraepithelial cervical neoplasm and parity, number of abortions and age at first or last birth.

Menstrual factors and the risk of epithelial ovarian cancer

The relationship between menstrual factors and the risk of ovarian cancer was evaluated in the framework of a hospital-based case-control study conducted in the greater Milan area on a total of 634 cases of ovarian cancer and 1626 control subjects with a spectrum of acute conditions unrelated to any of the established or potential risk factors for ovarian cancer. Compared with women whose menarche occurred at age 13 or later, the risk of ovarian cancer was moderately (and not significantly) elevated for earlier menarche (multivariate relative risk, RR = 1.13, 95% confidence interval, CI = 0.97-1.37). There was a positive association with age at menopause, the multivariate relative risk, compared with women aged 45 years or less at menopause, being 1.25 for those aged 45-49 years, 1.40 for 50-53 and 1.58 for 54 or over (chi 2(1) trend = 8.86, p = 0.003). A lifelong irregular menstrual pattern (defined as frequent menstrual-like episodes of bleeding less than 21 or more than 35 days apart) was negatively associated with the risk of ovarian cancer (multivariate RR = 0.45, 95% CI = 0.31-0.65). The effect of age at menopause and lifelong menstrual pattern was similar in different strata of age, whereas there was a positive association with early menarche among younger women which disappeared with advancing age. The present findings confirm the influence of various menstrual factors on the risk of epithelial ovarian cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral contraceptives and breast cancer. A review

Case-control and cohort studies published between 1977 and 1988 were reviewed with the purpose to evaluate the relationship between use of oral contraceptives (OC-use) and breast cancer risk, tumour biology and tumour prognosis with special emphasis on early OC-use. The risk of breast cancer was assessed in 30 case-referent studies and 5 cohort studies, and the prognosis of breast cancer had been studied in 9 reports. Definition of OC-use, prevalence of OC-use, latency time between start of OC-use and tumour diagnosis, case identification and choice of referents, study size, study quality were assessed. The outcome of the studies is presented. From the results of the analyses the author concludes that there is no overall risk for breast cancer among OC-users. However, with the emphasis on early OC-use, consistent results seem to emerge showing an increased risk of premenopausal breast cancer, when the possible bias of different latency times is taken into account. Also results on breast cancer incidence in early exposed age groups, tumour biology and prognosis in early OC-users with breast cancer support a genuine risk relationship. The effects of different OC-brands and dose, and the risk of peri- and postmenopausal breast cancer after early OC-use can at present not be assessed.