Nutritional factors and endometrial cancer in Ontario, Canada

Dietary lipids and endometrial cancer: the current epidemiologic evidence

BACKGROUND

Because dietary fat has been postulated to affect obesity and estrogen levels, two important risk factors for endometrial cancer, its association with this disease has received some attention. We summarize here the current evidence for several dietary lipids.

METHODS

Searches were conducted to identify peer-reviewed manuscripts up to December 2006. Two cohort studies and nine case-control studies were included in meta-analyses.

RESULTS

Random-effects summary estimates for case-control studies were 1.24 (95% CI: 1.10, 1.41) per 10% kcal from total fat and 1.28 (95% CI: 1.12, 1.47) per 10 g/1,000 kcal of saturated fat. The only cohort study evaluating total fat and saturated fat did not find an association. We estimated a 35% increased risk (95% CI: 0.96, 1.90) per 150 mg/1,000 kcal of cholesterol intake, based on six case-control studies. For animal fat (per 10 g/1,000 kcal) the summary estimates were 0.78 (95% CI: 0.63, 0.96) and 1.34 (95% CI: 1.06, 1.69) for two cohort and four case-control studies, respectively.

CONCLUSIONS

Case-control data suggest an increased risk for total, saturated, and animal fat. However, the limited available cohort data do not support these associations. Additional data, particularly from prospective studies, are needed before conclusions can be drawn.

Dietary patterns, Mediterranean diet, and endometrial cancer risk

This study examines the association between dietary patterns and endometrial cancer risk. A case-control study of endometrial cancer was conducted from 1996 to 1999 in the San Francisco Bay Area in white, African-American, and Latina women age 35-79. Dietary patterns were defined using a principal components analysis; scoring dietary intake based on correspondence to a Mediterranean-style diet; and by jointly categorizing intake of fruits/vegetables and dietary fat. Four dietary patterns were identified and labeled "plant-based," "western," "ethnic," and "phytoestrogen-rich." None of these dietary patterns nor adherence to a Mediterranean diet (to the extent consumed by this population) was associated with endometrial cancer risk. However, among non-users of supplements, greater consumption of the "western" dietary pattern was associated with a 60% increase in risk (95% CI: 0.95-2.7 per unit change; P-interaction = 0.10). A diet characterized by high fat consumption increased risk, regardless of fruit and vegetable consumption (OR = 1.4, 95% CI: 0.97-2.1 for high fat, low fruit/vegetable intake and OR = 1.4, 95% CI: 0.95-2.1 for high fat, high fruit/vegetable intake compared to low fat, high fruit/vegetable intake). Thus, while like others we found that dietary fat increases endometrial cancer risk, the evaluation of dietary patterns did not provide any additional information regarding risk.

Consumption of animal foods and endometrial cancer risk: a systematic literature review and meta-analysis

This article summarizes and quantifies the current evidence relating dietary intake of animal products and endometrial cancer. Literature searches were conducted to identify peer-reviewed manuscripts published up to December 2006. Twenty-two manuscripts from three cohort studies and 16 case-control studies were identified. One of these cohort studies evaluated only fried meat and another only milk consumption; they were not included in our meta-analyses. The third cohort study identified did not present exposure levels and could not be included in dose-response meta-analysis. This cohort study did not show an association with meat or red meat consumption. Random-effects dose-response summary estimates for case-control studies evaluating these foods were 1.26 (95% CI: 1.03-1.54) per 100 g/day of total meat, 1.51 (95% CI: 1.19-1.93) per 100 g/day of red meat, 1.03 (95% CI: 0.32-3.28) per 100 g/day of poultry, 1.04 (95% CI: 0.55-1.98) per 100 g/day of fish, and 0.97 (95% CI: 0.93-1.01) per serving of dairy. Our meta-analysis, based on case-control data, suggests that meat consumption, particularly red meat, increases endometrial cancer risk. The current literature does not support an association with dairy products, while the evidence is inconsistent for poultry, fish, and eggs. More studies, particularly prospective studies, are needed.

Fruits and Vegetables and Endometrial Cancer Risk: A Systematic Literature Review and Meta-Analysis

Endometrial cancer is the most common female gynecological cancer in the United States. Although obesity is a well-established risk factor, the role of other dietary factors is not well understood. The purpose of this study was to summarize and quantify the current evidence for fruit and vegetable intake and endometrial cancer by conducting a systematic literature review and meta-analysis. Searches were conducted to identify relevant papers published up to June 2006 in various databases. We included peer-reviewed manuscripts published in any language. Random and fixed-effects pooled risk estimates were estimated. We found one cohort study and 16 case-control studies evaluating various aspects of consumption. The random-effects summary estimates (95% CI) comparing high vs. low categories of intake reported were 0.71 (0.55-0.91) for total vegetables based on 10 studies, 0.85 (0.74-0.97) for cruciferous vegetables based on seven studies, and 0.90 (0.72-1.12) for total fruit based on 14 studies. For 100 g/day intake, summary ORs were 0.90 (0.86-0.95) for total vegetables, 0.79 (0.69-0.90) for cruciferous vegetables, and 0.97 (0.92-1.02) for total fruit. Excluding studies not meeting certain quality criteria provided similar results. The current evidence, based solely on case-control studies, with less than half being population-based, suggests a modest inverse association with vegetable consumption, particularly for cruciferous vegetables. We did not find any cohort studies evaluating fruit and vegetables separately. No firm conclusion can be drawn at this time in the absence of additional well-conducted population-based studies and, particularly, prospective data.

Nutritional factors in relation to endometrial cancer: a report from a population-based case-control study in Shanghai, China

We evaluated the role of dietary nutrients in the etiology of endometrial cancer in a population-based case-control study of 1,204 newly diagnosed endometrial cancer cases and 1,212 age frequency-matched controls. Information on usual dietary habits was collected during an in-person interview using a validated, quantitative food frequency questionnaire. Logistic regression analysis was conducted to evaluate the association of nutrients with endometrial cancer risk using an energy density method (e.g., nutrient intake/1,000 kilocalories of intake). Higher energy intake was associated with increased risk, which was attributable to animal source energy and a high proportion of energy from protein and fat. Odds ratios comparing highest versus lowest quintiles of intake were elevated for intake of animal protein (Odds ratio (OR) = 2.0, 95% confidential interval: 1.5-2.7) and fat (OR = 1.5, 1.2-2.0), but reduced for plant sources of these nutrients (OR = 0.7, 0.5-0.9 for protein and OR = 0.6, 0.5-0.8 for fat). Further analysis showed that saturated and monounsaturated fat intake was associated with elevated risk, while polyunsaturated fat intake was unrelated to risk. Dietary retinol, beta-carotene, vitamin C, vitamin E, fiber, and vitamin supplements were inversely associated with risk. No significant association was observed for dietary vitamin B1 or vitamin B2. Our findings suggest that associations of dietary macronutrients with endometrial cancer risk may depend on their sources, with intake of animal origin nutrients being related to higher risk and intake of plant origin nutrients related to lower risk. Dietary fiber, retinol, beta-carotene, vitamin C, vitamin E, and vitamin supplementation may decrease the risk of endometrial cancer.

Alcohol consumption, cigarette smoking, and endometrial cancer risk: results from the Netherlands Cohort Study

Objective

To examine the association between alcohol consumption, cigarette smoking, and endometrial cancer.

Methods

In 1986, the Netherlands Cohort Study was initiated. A self-administered questionnaire on dietary habits and other cancer risk factors was completed by 62,573 women. Follow-up for cancer was established by record linkage to the Netherlands Cancer Registry.

Results

After 11.3-years of follow-up, 280 incident endometrial cancer cases were available for analyses. In multivariate analysis, the rate ratio (RR) for alcohol users versus non-users was 1.06 (95% Confidence Interval (95% CI) = 0.78–1.43). There were neither dose-dependent trends nor associations with different types of beverages. The RR for former and current smokers versus never-smokers was 0.83 (95% CI = 0.58–1.20) and 0.59 (95% CI = 0.40–0.88), respectively. These estimates did not change significantly when body mass index (BMI) and age at menopause were added to the models.

Conclusions

There is no association between alcohol consumption and endometrial cancer. Current smoking is associated with a reduced risk of endometrial cancer. This association is neither mediated by BMI nor by age at menopause.

Dietary folate intake, MTHFR genetic polymorphisms, and the risk of endometrial cancer among Chinese women

Folate plays an important role in carcinogenesis. The enzyme 5,10-methylenetetrahydrofolate reductase (MTHFR), encoded by the MTHFR gene, is involved in this process. We investigated both the independent and joint effects of dietary folate and other methyl-related nutrients, as well as three polymorphisms of MTHFR (677C>T, 1298A>C, and 1793G>A), on endometrial cancer risk in a population-based case-control study. Between 1997 and 2003, 1,204 newly diagnosed endometrial cancer cases and 1,212 controls were recruited among women between the ages of 30 and 69 years in urban Shanghai, China. Information on dietary intake of folate and other methyl-related nutrients, including vitamin B2 (riboflavin), vitamin B6, vitamin B12, and methionine, was derived from a validated food frequency questionnaire. Genotyping was completed on 1,041 cases and 1,030 controls for MTHFR 677C>T (rs1801133), 1298A>C (rs1801131), and 1793 G>A (rs2274967) [corrected] Haplotype estimation of the three single-nucleotide polymorphisms was performed using PHASE software. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated to evaluate associations of nutrients, MTHFR genotypes, and haplotypes with endometrial cancer risk. A significant inverse association between dietary folate intake and endometrial cancer risk was observed among all subjects and non-B vitamin supplement users. The greatest reduction in endometrial cancer risk was observed among non-users of supplements in the highest quartile of dietary folate intake (OR, 0.5; 95% CI, 0.4-0.7) as compared with those in the lowest quartile. Dietary intake of folate cofactors (methionine, vitamin B2, vitamin B6, and vitamin B12) was not related to risk of endometrial cancer. No association was observed between endometrial cancer and the MTHFR 677C>T, 1298 A>C, and 1793G>A polymorphisms or derived haplotypes. Among non-users of supplements, however, the 1298C and 1793A alleles were associated with a lower risk of endometrial cancer among women with high dietary folate intake but related to a higher risk among those with low dietary folate intake (P(interaction) = 0.08 and 0.03, respectively). Further analysis showed that the lowest risk (OR, 0.6; 95% CI, 0.4-1.1) was among women with the 1298C allele and the highest intake of both folate and riboflavin (P(interaction) = 0.04). A similar association was observed for the 1793A allele (P(interaction) = 0.03). Our findings suggest that folate intake may decrease the risk of endometrial cancer and modify the effect of MTHFR polymorphisms on risk.

Fruit and vegetables in cancer prevention

Our aim was to review the epidemiological literature on possible cancer-preventive effects of the consumption of fruits and vegetables in humans, to quantify the effect of high versus low consumption of fruits and vegetables, and to give an overall assessment of the existing evidence. We based our work on an expert meeting conducted by the International Agency for Research on Cancer in 2003. A qualitative reading and evaluation of relevant articles on the cancer-preventive effect of the consumption of fruits and vegetables was made followed by the calculation of the mean relative risk and range for cohort and case-control studies separately. The possible population-preventable fraction for modifying diet in relation to fruit and vegetable consumption was calculated as well as an overall statement about the degree of evidence for the cancer-preventive effect of fruit and vegetable consumption for each cancer site. There is limited evidence for a cancer-preventive effect of the consumption of fruits and vegetables for cancer of the mouth and pharynx, esophagus, stomach, colon-rectum, larynx, lung, ovary (vegetables only), bladder (fruit only), and kidney. There is inadequate evidence for a cancer-preventive effect of the consumption of fruits and vegetables for all other sites. Applying this range of risk difference to the range of prevalence of low intake, the preventable fraction for low fruit and vegetable intake would fall into the range of 5-12%. It is important to recognize that this is only a crude range of estimates and that the proportion of cancers that might be preventable by increasing fruit and vegetable intake may vary beyond this range for specific cancer sites and across different regions of the world.

Smoking and the risk of endometrial cancer: results from the Nurses' Health Study

An inverse association between smoking and endometrial cancer has generally been observed, primarily among current smokers. To assess this association, we analyzed data from the prospective Nurses' Health Study. From 1976 to 2000, 702 cases of invasive endometrial cancer were identified during 1.8 million person-years of follow-up. Smoking status was assessed in 1976 and updated every 2 years. Cox proportional hazards models were used to calculate multivariate relative risks (RRs), controlling for endometrial cancer risk factors. Compared to never smokers, the multivariate RR of endometrial cancer was significantly lower among both current smokers (RR = 0.63; 95% CI = 0.50-0.79) and past smokers (RR = 0.73; 95% CI = 0.62-0.87). When additionally adjusting for body mass index (BMI), the RR for current smokers was attenuated (RR = 0.72; 95% CI = 0.57-0.90), but the RR for past smokers did not change. Risk was lower among women who smoked 35 or more cigarettes a day (RR = 0.60; 95% CI = 0.39-0.91) and among those who smoked for 40 or more years (RR = 0.63; 95% CI = 0.45-0.87). Tests for trend, which excluded never smokers, were not statistically significant for any of the smoking variables analyzed. These data indicate that both current and past smoking are associated with a lower risk of endometrial cancer. The findings provide insight into disease etiology and suggest that the influence of smoking on endometrial cancer risk occurs even in early adulthood, is long-lasting, and may not be attributed solely to short-term hormonal modulation.

Anthropometry, physical activity, and endometrial cancer risk: results from the Netherlands Cohort Study

Although obesity is an established risk factor for endometrial cancer, evidence linking risk to height, weight change since age 20, and physical activity is limited. In this case-cohort study, 62 573 women from The Netherlands Cohort Study on Diet and Cancer were followed up from 1986 to 1995, and 226 endometrial cancer case patients were identified. In Cox proportional hazards analyses, women 175 cm or taller had an increased risk of endometrial cancer compared with those less than 160 cm (rate ratio [RR] = 2.57, 95% confidence interval [CI] = 1.32 to 4.99). Compared with women with a body mass index (BMI; kg/m2) between 20 and 22.9, women with a BMI of 30 or greater had a higher risk (RR = 4.50, 95% CI = 2.62 to 7.72; P(trend)<.001). Moreover, BMI at age 20 and BMI gain since age 20 were positively associated with endometrial cancer risk (P(trend) = .02 and <.001, respectively). Women who spent 90 minutes per day or more doing nonoccupational physical activities had a lower risk (RR = 0.54, 95% CI = 0.34 to 0.85; P(trend) = .002) compared with those who spent less than 30 minutes per day. High BMI and low physical activity were strong and independent risk factors for endometrial cancer.

Other Gynecologic Cancers: endometrial, ovarian, vulvar and vaginal cancers

HEALTH ISSUE: In Canada, cancers of the endometrium, ovaries, vulva, vagina, placenta and adnexa account for 11% of all malignant neoplasms in women and 81% of all genital cancers. Although the incidence and mortality from vulvar and vaginal cancers are very low, endometrium and ovarian cancer are important public health problems. KEY FINDINGS: In Canada, there has been no appreciable improvement in survival for women with advanced endometrial (EC) or ovarian cancer (OC) over the past 30 years. The prognosis of EC is good for most patients because diagnosis is made at early stages. However, survival of OC is poor; more than 70% of cases are diagnosed at late stages. Up to 10% of OCs is linked to familial aggregation. Cancers of the vulva and of the vagina are very rare. The survival experience for women with the latter is worse than for those with the former. Both share many risk factors with cervical cancer and the recent developments in the study of HPV infection should be applicable to these diseases as well. Of particular interest will be the advent of vaccines for the primary prevention of HPV infection. DATA GAPS AND RECOMMENDATIONS: At present, the best available means to diagnose gynecologic malignancies is a detailed clinical examination, considering the totality of information on potential and proven risk factors, such as age, reproductive health, sexual practices, use unopposed estrogens or of oral contraceptives or tubal ligation, obesity, diet, smoking, and the familial clustering of some of these cancers.

Alcohol consumption and endometrial cancer: some unresolved issues

The role of hormonal factors, in particular unopposed estrogens, on endometrial cancer occurrence is well established. Progesterone deficiency has also been suggested as a possible risk factor. Alcohol use has been shown to be associated with elevated estrogen levels and reduced progesterone. Epidemiologic studies, however, have not offered much support for a positive association between alcohol intake and endometrial cancer, with results generally indicating no association or suggesting an inverse relationship with endometrial cancer. However, certain methodologic limitations, such as small sample size, limited range of alcohol intake, and confounding may have explained those findings. Moreover, there are some unexplored aspects of the possible effect of alcohol, such as the possible interaction with use of exogenous estrogens, and other factors, that need clarification.

Diet in relation to endometrial cancer risk: a case-control study in Greece

The risk of endometrial cancer is positively associated with obesity, but the role of specific nutrients remains unclear. Given the distinct characteristics of the Greek diet and the low incidence of this form of cancer among Greek women, we undertook a case-control study to investigate the association of endometrial cancer with food groups and micronutrients. Cases were 84 women with histologically confirmed endometrial cancer and controls were 84 women with intact uterus admitted to the same teaching hospital in Athens, Greece. Consumption of pulses, nuts, and seeds was significantly inversely related to the risk for endometrial cancer. No other significant association with food groups was detected, although a protective effect of added lipids, which in the Greek diet are primarily represented by olive oil, was highly suggestive. Retinol, nicotinic acid, vitamin B- 6, and riboflavin were inversely associated with the disease. These findings need to be replicated, because this was a relatively small study with the statistical power to detect only strong associations between cases and controls; they appear, however, to support a role of diet in the etiology of endometrial cancer.

Intakes of fish and marine fatty acids and the risks of cancers of the breast and prostate and of other hormone-related cancers: a review of the epidemiologic evidence

Marine fatty acids, particularly the long-chain eicosapentaenoic and docosahexaenoic acids, have been consistently shown to inhibit the proliferation of breast and prostate cancer cell lines in vitro and to reduce the risk and progression of these tumors in animal experiments. However, whether a high consumption of marine fatty acids can reduce the risk of these cancers or other hormone-dependent cancers in human populations is unclear. Focusing primarily on the results of cohort and case-control studies, we reviewed the current epidemiologic literature on the intake of fish and marine fatty acids in relation to the major hormone-dependent cancers. Despite the many epidemiologic studies that have been published, the evidence from those studies remains unclear. Most of the studies did not show an association between fish consumption or marine fatty acid intake and the risk of hormone-related cancers. Future epidemiologic studies will probably benefit from the assessment of specific fatty acids in the diet, including eicosapentaenoic and docosahexaenoic acids, and of the ratio of these to n-6 fatty acids, dietary constituents that have not been examined individually very often.

Dietary factors in relation to endometrial cancer: a nationwide case-control study in Sweden

The incidence of endometrial cancer varies up to 10-fold between high- and low-incidence regions, suggesting the importance of environmental factors, including diet, in the etiology of this disease. However, few studies have examined the role of diet in the etiology of endometrial cancer. Using unconditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI), we analyzed data from a large, case-control study of Swedish-born postmenopausal women aged 50-74 yr (709 cases and 2,887 controls) residing in Sweden between 1994 and 1995. We found no clear association between foods or food groups and endometrial cancer risk, although high consumption of certain foods, such as Brassica vegetables, coffee, and legumes, might be associated with small-to-moderate reduced risks of endometrial cancer, while red meat consumption might be associated with a small-to-moderate increased risk. Daily use of calcium supplements appeared to lower endometrial cancer risk (OR = 0.5, 95% CI = 0.3-0.9, P for trend = 0.04), especially among women with low calcium intake from dairy products. On the other hand, the use of iron supplements appeared to increase the risk (OR = 1.7, 95% CI = 0.9-3.3, P for trend = 0.03). The findings are discussed with respect to previous studies and the possible underlying mechanisms.

Cigarette smoking and the risk of endometrial cancer

Epidemiological studies have shown that cigarette smoking is associated with a reduced risk of endometrial cancer, in contrast to the increased risks observed with many other non-respiratory-tract cancers, including those of the bladder, pancreas, and cervix uteri. Some studies of endometrial cancer suggest that the inverse association with smoking is limited to certain groups of women, such as those who are postmenopausal or those taking hormone-replacement therapy. The biological mechanisms that might underlie this association remain unclear, although several have been proposed, including an antioestrogenic effect of cigarette smoking on circulating oestrogen concentrations, a reduction in relative bodyweight, and an earlier age at menopause. We have examined the evidence for an association between cigarette smoking and risk of endometrial cancer, including studies related to the proposed biological mechanisms.

Diet and environmental carcinogenesis in breast/gynaecological cancers

This paper reports on recent advances on the relation between diet, other environmental factors and breast and gynaecological cancers. Despite considerable research the issue remains still unsettled. The protective effect of a diet rich in vegetables and fruit, and thus selected (antioxidant) micronutrients, is not consistently reported in various studies. The possible relationship between fats and breast and female genital tract neoplasms also remains unconfirmed, while the potential benefits of physical activity remains unquantified. Alcohol appears to be related to the risk of breast cancer and overweight is associated with post-menopausal breast cancer and is strongly related to the risk of endometrial cancer.

Fruit and vegetable consumption in the prevention of cancer: an update

Fruit and vegetables are considered to be important means of preventing cancer through diet. However, several recent large prospective cohort studies and clinical trials have found no associations regarding several major cancers, including cancers of the colon, breast and stomach. Although these results are disconcerting, especially for health-conscious individuals, there is also mounting evidence that people who avoid fruit and vegetables completely, or consume very little, are indeed at increased risk of these cancers. These individuals in particular should be identified, with the goal of helping them find ways to include more fruit and vegetables in their diets.