Menstrual and reproductive factors in relation to ovarian cancer risk

Dietary risk factors for ovarian cancer: the Adventist Health Study (United States)

Few prospective studies have reported dietary risk factors for ovarian cancer. A total of 71 histologically confirmed epithelial ovarian cancers occurred among 13,281 non-Hispanic white California Seventh-day Adventist women during follow-up. Participants were part of the Adventist Health Study (AHS) and had no history of cancer or hysterectomy at baseline in 1976 when they completed a detailed lifestyle questionnaire including a dietary assessment. The association of dietary variables with either all ovarian cancer cases or postmenopausal cases was tested using proportional hazards regression with adjustment for age and other covariates. The strongest hazardous risk factor associations among the food variables were found for meat intake with a risk ratio (RR) of 2.42 for intake > or = 1 time/week versus no meat (p for trend = 0.006), and cheese intake with a RR of 2.02 for intake of > 2 time/week versus < 1 per week (p for trend = 0.10), both of these being in postmenopausal cases. We found significantly reduced risk of all ovarian cancer with higher tomato consumption (RR = 0.32) comparing intakes > or = five times/week versus never to < 1 time/week (p for trend = 0.002), and also with higher fruit consumption (p < 0.01). A weak protective association was found with low fat, but not whole milk. Little confounding was observed between these foods.

Recreational physical activity and sedentary behavior in relation to ovarian cancer risk in a large cohort of US women

Factors that influence circulating sex hormones, such as physical activity, have been proposed to influence ovarian cancer risk; however, results from previous epidemiologic studies have been inconsistent. The authors examined the association among physical activity, sedentary behavior, and ovarian cancer risk in the American Cancer Society Cancer Prevention Study II Nutrition Cohort, a prospective study of cancer incidence and mortality, using information obtained at baseline in 1992. From 1992 to 2001, 314 incident ovarian cancer cases were identified among 59,695 postmenopausal women who were cancer free at enrollment. Cox proportional hazards modeling was used to compute hazard rate ratios while adjusting for potential confounders. No overall association was observed between measures of past physical activity or with recreational physical activity at baseline and risk of ovarian cancer in this study (for the highest category of physical activity compared with none: hazard rate ratio = 0.73, 95% confidence interval: 0.40, 1.34). However, a prolonged duration of sedentary behavior was associated with an increased risk (for > or = 6 vs. < 3 hours per day: hazard rate ratio = 1.55, 95% confidence interval: 1.08, 2.22; p(trend) = 0.01). Results from this study suggest that high levels of sedentary behavior may increase the risk of ovarian cancer, but they do not support a major impact of light and moderate physical activity on ovarian cancer risk.

Prevention of ovarian cancer

Ovarian cancer is the leading cause of death from gynaecological malignancy. The incidence is high in the Western world. The incidence of ovarian cancer is reduced by pregnancy, lactation, the oral contraceptive pill and tubal ligation. Lifestyle factors are important in the aetiology of ovarian cancer and current evidence suggests the risk can be reduced by eating a diet rich in fruit and vegetables, taking regular exercise, avoiding smoking, avoiding being overweight and avoiding long-term use of hormonal replacement therapy (HRT). Familial ovarian cancer is responsible for about 10% of ovarian cancer cases. Strategies available to high-risk women include screening (covered elsewhere) and prophylactic salpingo-oophorectomy. The precise role of chemoprevention for high-risk women in the form of the oral contraceptive pill is unclear.

Incessant ovulation, inflammation and epithelial ovarian carcinogenesis: revisiting old hypotheses

Epithelial ovarian cancer (EOC) is often a lethal disease because in many cases early symptoms go undetected. Although research proceeds apace, as yet there are few reliable and specific biomarkers for the early stages of the disease. EOC is an umbrella label for a highly heterogeneous collection of cancers, which includes tumours of low malignant potential, serous cystadenomas, mucinous and clear cell carcinomas, all of which are likely to arise from a number of epithelial cell types and a variety of progenitor lesions. Many, but not all types of EOC are thought to arise from the cells lining ovarian inclusion cysts. In this review, we discuss the hypotheses that have driven our ideas on epithelial ovarian carcinogenesis and examine the morphological and genetic evidence for pathways to EOC. The emergence of laser-capture microdissection and expression profiling by microarray technologies offers the promise of defining these pathways more accurately, as well as providing us with the tools for earlier diagnosis.

Height, age at menarche, and risk of epithelial ovarian cancer

OBJECTIVE

We hypothesized that the hormonal changes of adolescence influence ovarian cancer risk particularly in younger women. We investigated this possibility by examining the relationship between ovarian cancer and adult height and age at menarche as both factors reflect pubertal hormonal levels.

METHODS

Participants were a population-based sample of women with incident ovarian cancer (n=794) and control women randomly selected from the Australian Electoral Roll (n=855). The women provided comprehensive reproductive and lifestyle data during a standard interview.

RESULTS

Although neither height nor age at menarche was significantly related to the risk of ovarian cancer overall, increasing height was associated with increasing risk of the subgroup of mucinous borderline ovarian cancer (odds ratio, 5.3; 95% confidence interval, 1.5-19.1 for women>or=175 cm compared with women <160 cm, Ptrend=0.02). Similarly, later age at menarche was associated with increasing risk of mucinous borderline cancers (odds ratio, 3.8; 95% confidence interval, 1.3-11.4 for those with age at menarche>or=14 years compared with those <12 years, Ptrend=0.003). Women with mucinous borderline cancers were significantly younger than the women diagnosed with invasive cancers (mean 44 versus 57 years; P<0.0001).

CONCLUSIONS

Development of mucinous borderline ovarian cancers, predominantly diagnosed in women ages under 50 years, seems to be associated with age at menarche and attained adult height. These results are consistent with our original hypothesis that pubertal levels of reproductive hormones and insulin-like growth factor-I influence ovarian cancer risk in younger women.

Fruit and Vegetable Consumption and Risk of Epithelial Ovarian Cancer: The European Prospective Investigation into Cancer and Nutrition

OBJECTIVE

The association between consumption of fruit and vegetables and risk of ovarian cancer is still unclear from a prospective point of view.

METHODS

Female participants (n = 325,640) of the European Prospective Investigation into Cancer and Nutrition study, free of any cancer at baseline, were followed on average for 6.3 years to develop ovarian cancer. During 2,049,346 person-years, 581 verified cases of primary, invasive epithelial ovarian cancer were accrued. Consumption of fruits and vegetables as well as subgroups of vegetables, estimated from validated dietary questionnaires and calibrated thereafter, was related to ovarian cancer incidence in multivariable hazard regression models. Histologic subtype specific analyses were done.

RESULTS

Total intake of fruit and vegetables, separately or combined, as well as subgroups of vegetables (fruiting, root, leafy vegetables, cabbages) was unrelated to risk of ovarian cancer. A high intake of garlic/onion vegetables was associated with a borderline significant reduced risk of this cancer. The examination by histologic subtype indicated some differential effects of fruit and vegetable intake on ovarian cancer risk.

CONCLUSION

Overall, a high intake of fruits and vegetables did not seem to protect from ovarian cancer. Garlic/onion vegetables may exert a beneficial effect. The study of the histologic subtype of the tumor warrants further investigation.

Hormone replacement therapy and invasive and borderline epithelial ovarian cancer risk

Risk of epithelial ovarian cancer (EOC) attendant to use of hormone replacement therapy (HRT) was evaluated in a population-based case-control study of newly diagnosed EOC cases (n=256) and randomly selected population controls (n=1122). Telephone interviews were conducted to obtain information on history of HRT and several other covariates. Multivariate adjusted odds ratio (OR) and 95% confidence intervals (CI) were derived from unconditional logistic regression. The OR for ever use of HRT was 1.39 (95% CI: 1.01-1.93) compared to never use. Long-term use (>10 years) increased risk (OR: 1.62, CI: 1.05-2.50) although the trend p-value for duration of use was of only borderline significance (p=0.08). The relationship was stronger in women without hysterectomy (OR: 1.66, 95% CI: 1.14-2.41) or tubal ligation (OR: 1.56, 95% CI: 1.08-2.26). In this study, use of HRT is associated with an increased risk of EOC.

Breastfeeding and the risk of epithelial ovarian cancer in an Italian population

OBJECTIVES

Breastfeeding has been inversely related to the risk of ovarian cancer, but results from published studies are inconsistent. In order to provide further information, we analyzed data from a large case-control study conducted in four Italian areas.

METHODS

Cases were 1031 women with epithelial ovarian cancer. Controls were 2411 women admitted to the same network of hospitals for a wide spectrum of acute non-neoplastic conditions, unrelated to known risk factors for ovarian cancer.

RESULTS

There were inverse trends in risk with increasing duration of breastfeeding and number of children breastfed, but when parity and several other potential confounding factors were taken into account, no residual association was evident (odds ratio = 1.21 for 17 or more months of breastfeeding and 0.90 for those who had breastfed 4 or more children, as compared to women who had never breastfed).

CONCLUSIONS

This study showed an inverse relation between breastfeeding and ovarian cancer risk, which however was accounted for by parity. The analyses by histologic subtypes suggested that a role of breastfeeding would be larger for serous neoplasms in the absence, however, of significant heterogeneity.

Mathematical Models of Ovarian Cancer Incidence

BACKGROUND

Pike has proposed "protected time" as one summary method for modeling reproductive risk factors in relation to ovarian cancer incidence. We evaluate this and other approaches to summarizing risk for ovarian cancer.

METHODS

We identified 472 incident cases of ovarian cancer during 2,298,068 person-years of follow-up of 24- to 55-year-old premenopausal women at cohort inception. Reproductive exposures, use of oral contraceptives, and history of tubal ligation were evaluated.

RESULTS

Age at menopause is directly related to cumulative risk of ovarian cancer up to age 70 years (age 55 vs. age 45, risk increase = 62%; 95% confidence interval = 36 to 96%) and age at menarche is inversely related to risk (age 15 vs. 11, risk reduction = 31%; 27-34%). Use of oral contraceptives for 5 years before age 30 decreases risk of ovarian cancer to age 70 by 37% (32 to 41%). Tubal ligation reduces risk up to age 70 by 21% (-2 to 38%). Parity reduces risk, independent of age at first birth and age at last birth. A model summarizing years of ovulation offers a fit comparable to a more complex modeling of reproductive variables. The model fit is good, with a concordance statistic of 0.60 (0.57 to 0.62) indicating reasonable ability to differentiate those who will develop ovarian cancer from those who will remain disease free.

CONCLUSION

This model may be applied in the identification of women at high risk for ovarian cancer, for example, in selecting candidates for prevention trials.

Relations of Gestational Length and Timing and Type of Incomplete Pregnancy to Ovarian Cancer Risk

While the protective nature of parity with respect to ovarian cancer has been well documented, whether a history of incomplete pregnancy affects ovarian cancer risk is uncertain. Data collected from 739 epithelial ovarian cancer cases and 1,313 community controls in the Delaware Valley from 1994 to 1998 were used to evaluate the relation between gestational length and timing of first induced or spontaneous abortion and ovarian cancer risk. Incomplete pregnancy was not associated with ovarian cancer among nulliparous women or among ever-pregnant women either before or after adjustment for relevant confounders (for nulliparous women, odds ratio (OR) = 1.12, 95% confidence interval (CI): 0.66, 1.89; for ever-pregnant women, OR = 0.95, 95% CI: 0.76, 1.18). Among unigravid women, one full-term pregnancy was more protective than an incomplete pregnancy (adjusted OR = 0.29, 95% CI: 0.15, 0.57). These results were independent of the type of pregnancy loss. Among ever-pregnant women, a spontaneous abortion before a first birth provided significant protection (adjusted OR = 0.47, 95% CI: 0.30, 0.75), while no significant effect was found for an induced abortion prior to a first birth (adjusted OR = 0.80, 95% CI: 0.44, 1.47). These data do not support an independent association between incomplete pregnancies, either spontaneous or induced, and ovarian cancer risk.

Clarifying the PROGINS Allele Association in Ovarian and Breast Cancer Risk: A Haplotype-Based Analysis

BACKGROUND

The PROGINS allele of the progesterone receptor (PGR) gene has been associated with an increased risk of ovarian cancer and a decreased risk of breast cancer. We set out to refine the association between common variation at the PGR gene locus and these two diseases.

METHODS

We characterized the haplotype structure of the PGR gene by genotyping 54 single-nucleotide polymorphisms (SNPs) in 349 women. We then selected a subset of 17 haplotype-tagging SNPs that captured variation across the locus and typed them in 267 ovarian cancer case patients and 397 control subjects from two case-control studies and in 1715 breast cancer case patients and 2505 control subjects from a cohort study.

RESULTS

The PGR locus was characterized by four blocks of strong linkage disequilibrium. Two SNPs in block 4 were associated with an increased risk of ovarian cancer among homozygous carriers as compared with noncarriers: rs1042838 (PROGINS allele; odds ratio [OR] = 3.23, 95% confidence interval [CI] = 1.19 to 8.75, P = .022) and rs608995 (minor allele; OR = 3.10, 95% CI = 1.63 to 5.89, P<.001). The PROGINS allele was observed on a subset of chromosomes carrying the minor allele at rs608995, and its association with ovarian cancer was fully explained by its association with rs608995. In addition, rs608995 fell on two common haplotypes (4-D and 4-E), whose association with ovarian cancer was the same as that of rs608995. These same two haplotypes were associated with a non-statistically significantly reduced risk of breast cancer.

CONCLUSIONS

Variation in PGR was associated with ovarian cancer risk, although the strongest result was not with the PROGINS allele. Instead, any causal allele(s) are likely in or downstream of block 4 and carried on haplotypes 4-D and 4-E. There was some evidence that the same variation was associated with a reduced risk of breast cancer, but the association was not statistically significant.

Endogenous Hormones and Ovarian Cancer: Epidemiology and Current Hypotheses

The effect of major epidemiologic risk factors for ovarian cancer has been reviewed in the light of several hormonal hypotheses, including the gonadotropin, androgens, progesterone, estrogens, insulin-like growth factor-I, and insulin hypotheses. The role of inclusion cyst formation and Mullerian epithelium differentiation in the pathology of the disease are also briefly outlined. Although based on limited data, the observed tendency in current evidence suggests possible etiologic roles for elevated androgens and estrogens and decreased progesterone in the pathogenesis of ovarian cancer. A direct effect of gonadotropins cannot be entirely ruled out, but it is plausible that their effect on ovarian cancer risk is mediated by stimulation of ovarian steroidogenesis. Insulin-like growth factor-I also emerges as a hormone that may be directly involved in the pathogenesis of the disease, but thus far only one prospective study has examined this association. Hyperinsulinemia is an unlikely risk factor for ovarian cancer. The observed tendency for an increased risk with androgens from ovarian origin (in premenopausal women), the lack of association with adrenal androgens, and the relatively weak associations observed with obesity, hormonal replacement therapy use, and endogenous hormones after menopause suggest that ovarian synthesis of sex steroids rather than their circulating levels may be etiologically important. More data from prospective studies will be crucial to improve our understanding of the etiologic role of endogenous hormones in the pathogenesis of ovarian cancer. Such data will ultimately provide opportunities for research targeted; at early detection and preventive interventions.

Common risk factors of breast and ovarian cancer: recent view

Clinicians, epidemiologists, and public health specialists tend to examine breast and ovarian cancer separately. Although this seems fairly rational and expected, both malignancies are estrogen related and thus share many risk factors. In this review, we investigate the common familial, reproductive, anthropometric, nutritional, and lifestyle risk factors of breast and ovarian cancer. We believe that the parallel examination of the two cancer types could significantly contribute to an improved prevention of "gynecological cancer" as a whole.

Prolonged lactation reduces ovarian cancer risk in Chinese women

To investigate the effect of lactation on the risk of ovarian cancer for Chinese women, a case-control study was conducted in Hangzhou, capital of Zhejiang province, China. Cases were 275 patients with histologically confirmed epithelial ovarian cancer. Controls were 623 women without neoplasm. All participants were parous women who had given at least one live birth and had been residents of Zhejiang province for at least 10 years. Information was collected using a validated and reliable questionnaire on total months of lactation, number of children breastfed, and average duration of lactation per child. Multivariate logistic regression models were used to assess the association between ovarian cancer risk and lactation variables, accounting for age, locality, full-term pregnancy, oral contraceptive use and family history of the cancer. The adjusted odds ratios were 0.51 (95% confidence interval (CI) 0.3-0.9) and 0.44 (95% CI 0.2-0.9) respectively for women with over 12 months of lactation and at least three children breastfed, compared with those with 4 months or less lactation and one child breastfed. The corresponding dose-response relationships were also significant (P<0.05). Therefore, prolonged lactation could reduce the risk of ovarian cancer for Chinese women.

Epithelial ovarian cancer risk by invasiveness and cell type in the Central Valley of California

OBJECTIVE

To evaluate epithelial ovarian cancer (EOC) risk factors by level of invasiveness and histology.

METHODS

A population-based epidemiologic case-control study of EOC was conducted over a 2-year period (January 2000 to December 2001) in 22 counties of Central California that comprise the reporting area for two regional cancer registries. Telephone interviews were conducted with 256 cases and 1122 control frequencies matched on age and ethnicity. The interview obtained information on demographic factors as well as information pertinent to the respondent's menstrual and reproductive experience, use of exogenous hormones, surgical history, and family history of cancer. Adjusted odds ratios were calculated using stratification as well as Logistic regression methods. Analyses were completed by level of invasiveness and cell type.

RESULTS

Strong protective associations were observed for use of oral contraceptives and parity. Risk increased with a family history of ovarian, but not breast cancer and age at first birth was positively associated with increased risk. Hormone replacement therapy was associated with increased risk only in long-term users. Many of the relationships were observed only in specific histologic subtypes of EOC.

CONCLUSION

Risk of EOC is associated with several lifestyle and environmental exposures but the impact of these effects appears to be dependent upon level of invasiveness and histologic subtypes of EOC. However, the sample size available for analysis limits our statistical power and our ability to analyze data by histologic subtype, thus limiting interpretation of our results.

Prevention of cancers of the breast, endometrium and ovary

A central epidemiological feature of cancers of the breast, endometrium and ovary is the sharp slowing down in their rate of increase with age around the time of menopause. The incidence of these tumors by the age of 70 years would be between fourfold and eightfold increased if the rapid increase with age seen in young women continued into old age. These phenomena can be explained by the different effects of ovarian hormones on cell division rates in the relevant tissues. Models of these effects provide a plausible explanation of most of the known epidemiology of each of the cancers, including the increase in breast cancer risk from menopausal estrogen-progestin therapy. Some recent epidemiological findings in endometrial and ovarian cancer suggest new avenues for possible chemoprevention of these cancers.

Hormonal factors and the risk of invasive ovarian cancer: a population-based case-control study

OBJECTIVE

To examine the influence of hormone-related factors on the risk of invasive epithelial ovarian cancer (ovarian cancer).

DESIGN

Population-based case-control study using in-person interviews.

SETTING

Academic department of preventive medicine.

PATIENT(S)

Four hundred seventy-seven ovarian cancer patients and 660 controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Numbers of and ages at births, oral contraceptive use, and use of menopausal hormone therapy.

RESULT(S)

Compared with nulliparous women, women whose only (last) birth was after age 35 years had an estimated 51% (95% confidence interval: 21%-70%) reduction in risk. If this birth occurred earlier, the reduction in risk was progressively less. Additional (earlier) births reduced the risk further. Oral contraceptive use also reduced risk. Increased body mass index increased risk, but this effect was confined to localized disease and is likely to be a diagnostic bias, as a consequence of other problems associated with being overweight and in itself having no etiological significance.

CONCLUSION(S)

If the major protective effect of a late birth can be confirmed, our most challenging task will be to understand the mechanism to develop a chemoprevention approach to exploit this finding.

Does pregnancy induce the shedding of premalignant ovarian cells?

BACKGROUND

High parity is associated with reduced risk of ovarian cancer. One hypothesis is that pregnancy is associated with clearance of a fraction of the genetically modified (premalignant) cells from the ovaries.

METHODS

We evaluated this hypothesis using a model that estimates the cell clearance fraction at first and second pregnancy according to age at pregnancy. The model was fitted using reproductive history data from a cohort of 1.5 million Danish women born between 1935 and 1978 and followed for 28.7 million person-years. During this follow-up period, 2,035 developed invasive ovarian cancer.

RESULTS

We found the model to have a satisfactory fit despite the very few parameters involved. The model estimated similar cell clearance fractions for the first and second pregnancy and decreasing clearance with later age at pregnancy.

CONCLUSION

The relation of pregnancy history to risk of ovarian cancer can be well described by a cell clearance model that allows the cell clearance fraction to decrease with age at pregnancy.

A comprehensive look at the early detection of ovarian cancer

Ovarian cancer is the leading cause of gynecologic cancer deaths and the fifth leading cause of cancer deaths among American women. Advances in surgery and treatment modalities have slightly improved five-year survival rates, but the prognosis for most women continues to be poor. Rectovaginal examination, ultrasound, and the CA-125 blood test are three modalities currently used to screen for ovarian cancer, although no universal ovarian cancer screening guidelines are recommended for the general population. Developments in the early detection of ovarian cancer are emerging and include blood tests that could lead to identifying asymptomatic, early-stage ovarian cancer. Nurses should be knowledgeable about these developments in ovarian cancer as they educate women about ovarian cancer risk, prevention, and early detection.