Risk of ovarian cancer in relation to prediagnostic levels of C-peptide, insulin-like growth factor binding proteins-1 and -2 (USA, Sweden, Italy)

OBJECTIVE

To investigate the association of prediagnostic circulating levels of C-peptide, as a marker of pancreatic insulin secretion, and IGF binding proteins -1 and -2, as indicators of the biologically active IGF-I concentration, with risk of developing ovarian cancer.

METHODS

The study was nested within three prospective cohorts in New York (USA), Umeå (Sweden) and Milan (Italy). Case subjects were 132 women with primary invasive epithelial ovarian cancer diagnosed at least one year after blood donation. For each case, two control subjects were selected, matching the case subject on cohort, menopausal status, age and date of recruitment (n = 263). Only women who did not use exogenous hormones at blood donation were included in the study.

RESULTS

Odds ratios and their 95% confidence intervals for risk of developing ovarian cancer over quartiles of peptides concentrations after adjustment for BMI and fasting were: 1.00, 0.66 (0.35-1.23), 0.96 (0.51-1.82) and 0.89 (0.44-1.81) for C-peptide; 1.00, 1.10 (0.58-2.09), 1.07 (0.55-2.04) and 0.79 (0.38-1.62) for IGFBP-1; and 1.00, 1.01 (0.54-1.89), 0.98 (0.51-1.88) and 0.87 (0.45-1.68) for IGFBP-2. In women who had ovarian cancer diagnosis before age 55 the ORs for the top tertiles of IGFBP-1 and IGFBP-2 were 0.51 (0.18-1.49) and 0.53 (0.18-1.54), respectively.

CONCLUSIONS

This study does not support an independent direct etiological role of C-peptide in ovarian cancer pathogenesis, but suggests a possible protective effect of circulating IGFBP-1 and -2 in women who develop ovarian cancer before age 55.

Circulating levels of sex steroid hormones and risk of endometrial cancer in postmenopausal women

Experimental and epidemiological data support a role for sex steroid hormones in the pathogenesis of endometrial cancer. The associations of pre-diagnostic blood concentrations of estradiol, estrone, testosterone, androstenedione, DHEAS and SHBG with endometrial cancer risk were investigated. A case-control study was nested within 3 cohorts in New York (USA), Umeå (Sweden) and Milan (Italy). Cases were 124 postmenopausal women with invasive endometrial cancer. For each case, 2 controls were selected, matching the case on cohort, age and date of recruitment. Only postmenopausal women who did not use exogenous hormones at the time of blood donation were included. Odds ratios (OR) and their 95% confidence intervals (CI) were estimated by conditional logistic regression. ORs (95% CI) for endometrial cancer for quartiles with the highest hormone levels, relative to the lowest were as follows: 4.13 (1.76-9.72), p(trend) = 0.0008 for estradiol, 3.67 (1.71-7.88), p(trend) = 0.0007 for estrone, 2.15 (1.05-4.40), p(trend) = 0.04 for androstenedione, 1.74 (0.88-3.46), p(trend) = 0.06 for testosterone, 2.90 (1.42-5.90), p(trend) = 0.002 for DHEAS and 0.46 (0.20-1.05), p(trend) = 0.01 for SHBG after adjustment for body mass index, use of oral contraceptives and hormone replacement therapy. The results of our multicenter prospective study showed a strong direct association of circulating estrogens, androgens and an inverse association of SHBG levels with endometrial cancer in postmenopausal women. The effect of elevated androstenedione and testosterone levels on disease risk seems to be mediated mainly through their conversion to estrogens, although an independent effect of androgens on tumor growth cannot be ruled out, in particular in the years close to diagnosis.

Prediagnostic levels of C-peptide, IGF-I, IGFBP -1, -2 and -3 and risk of endometrial cancer

Conditions related to chronic hyperinsulinemia, such as obesity, noninsulin dependent diabetes mellitus and polycystic ovary syndrome, are associated with an increased risk of endometrial cancer. Elevated plasma IGF-I and decreased levels of IGF-binding proteins have been shown to be associated with increased risk of several cancer types that are frequent in affluent societies. We investigated for the first time in a prospective study the association of pre-diagnostic blood concentrations of C-peptide (a marker of pancreatic insulin production), IGF-I, IGFBP-1, -2 and -3 with endometrial cancer risk. A case-control study was nested within 3 cohorts in New York (USA), Umeå (Sweden) and Milan (Italy). It included 166 women with primary invasive endometrial cancer and 315 matched controls, of which 44 case and 78 control subjects were premenopausal at recruitment. Endometrial cancer risk increased with increasing levels of C-peptide (ptrend = 0.0002), up to an odds ratio (OR) of 4.76 [95% confidence interval (CI) = 1.91-11.8] for the highest quintile. This association remained after adjustment for BMI and other confounders [OR for the top quintile = 4.40 (1.65-11.7)]. IGFBP-1 levels were inversely related to endometrial cancer [ptrend = 0.002; OR in the upper quintile = 0.30 (0.15-0.62)], but the association was weakened and lost statistical significance after adjustment for confounders [ptrend = 0.06; OR in the upper quintile = 0.49 (0.22-1.07)]. Risk was unrelated to levels of IGF-I, IGFBP-2 and IGFBP-3. Chronic hyperinsulinemia, as reflected by increased circulating C-peptide, is associated with increased endometrial cancer risk. Decrease in the prevalence of chronic hyperinsulinemia, through changes in lifestyle or medication, is expected to prevent endometrial cancer.

Reliability of serum iron, ferritin, nitrite, and association with risk of renal cancer in women

Reliability of serum levels of iron, ferritin and nitrite (NO(2)(-)) over a 2-year period were evaluated in 40 healthy women (20 pre-menopausal and 20 post-menopausal), ages 39-65 years, from the New York University Women's Health Study (NYUWHS). Three blood samples per woman collected at yearly intervals were analyzed. Reliability coefficients (RCs) of serum iron, ferritin, and nitrite were 0.03 (95% confidence interval (CI), 0-0.33), 0.90 (95% CI, 0.79-0.95), and 0.72 (95% CI, 0.50-0.86), respectively, for pre-menopausal women, and 0.26 (95% CI, 0-0.56), 0.77 (95% CI, 0.59-0.89), and 0.55 (95% CI, 0.30-0.77), respectively, for post-menopausal women. In a case-control study nested within NYUWHS cohort, serum levels of nitrite, ferritin, and iron were measured in women apparently healthy at the time of blood donation but diagnosed with renal cancer 1.8-12.2 years later (n=24) and in individually matched controls (two per case). The results suggest that high serum levels of ferritin and nitrite may be associated with a decreased risk of renal cancer (odds ratio (OR), 0.55, 95% CI, 0.15-2.01 for ferritin, and OR, 0.52, 95% CI, 0.17-1.60 for nitrite in women with above median level as compared to women with below median level). The possible role of ferritin and nitrite in renal cancer is discussed.

Serum fatty acids and risk of breast cancer in a nested case-control study of the New York University Women's Health Study

Migrant and experimental animal studies suggest that differences in breast cancer incidence rates may be related, in part, to intake of dietary fat. The experimental evidence indicates that total fat, saturated, and n-6 polyunsaturated fatty acids (PUFAs) may stimulate both mammary tumor growth and metastasis, whereas n-3 PUFAs may have a tumor-inhibiting effect. Overall, epidemiological studies do not appear to confirm such observations. Within a cohort of women in the New York University Women's Health Study, the fatty acid composition of serum phospholipids was analyzed by gas chromatography among 197 pre- and postmenopausal clinically identified breast cancer subjects and their matched controls. Individual fatty acids in serum phospholipids were expressed as a percentage of total fatty acids. No significant difference was observed in the proportion of saturated fatty acids (SFAs), monounsaturated fatty acids, or n-6 and n-3 PUFAs between cases and controls. After menopause, total SFAs were positively associated with the risk of breast cancer [odds ratio (OR) = 1.96, 95% confidence interval (CI): 0.73-5.25; P = 0.05] after adjustment for potential confounding factors. Myristc acid (C14:0) was suggestive of a small increase in breast cancer risk in premenopausal women (OR = 2.22, 95% CI: 0.78-6.31), whereas palmitic acid (C16:0) showed similar trends in postmenopausal women (OR = 2.57, 95% CI: 0.99-6.61). Overall, total PUFAs (n-6 and n-3) were suggestive of a small protective effect (OR = 0.59, 95% CI: 0.31-1.09). No significant associations were found between other fatty acids and the risk of breast cancer. The study suggested evidence of an association between serum levels of SFAs and the risk of breast cancer in postmenopausal women. Neither individual n-3 fatty acids of marine origin, eicosapentaenoic acid (C20:5 n-3), and docosahexaenoic acid (C22:6 n-3), nor n-6 PUFAs were related to cancer risk in this study.

Characterization of dioxin exposure in residents of Chapaevsk, Russia

Since 1967, a chemical plant in the town of Chapaevsk (Samara province, Russia) has produced large amounts of chlorinated compounds and is suspected to be a major source of local environmental dioxin contamination. Dioxins have been detected in the local air, soil, drinking water, vegetables, and cow's milk. Human exposure to dioxins is suspected as a factor in the deteriorating local public health. In an effort to characterize nonoccupational dioxin exposure among local residents, during the summer of 1998, 24 volunteers were recruited to donate blood and to provide information about their residence, employment, demographics, medical history, and dietary habits. Selected polychlorinated dibenzodioxins, dibenzofurans, and coplanar biphenyls were measured in blood serum samples. The mean concentration of total dioxin World Health Organization toxic equivalents (WHO-TEQ(98)) based on polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) was 61.2 (range 16.4-168.1) pg/g lipid. Subjects living in close proximity to the plant (less than 5 km) had significantly higher dioxin levels (mean WHO-TEQ(98), 75.7 pg/g lipid), as compared to subjects living more than 5 km from the plant (mean WHO-TEQ(98), 44.1 pg/g lipid) (P<0.04). Comparisons of the study results with available published data indicate that average blood dioxin levels were substantially higher in Chapaevsk residents than in nonoccupationally exposed populations of other parts of Russia, Europe, and North America. Chronic exposures of such magnitude may have appreciable adverse effects on public health.

Circulating levels of insulin-like growth factor-I and risk of ovarian cancer

Insulin-like growth factor (IGF)-I, a mitogenic and anti-apoptotic peptide, has been implicated in the development of several cancers. We hypothesized that high circulating IGF-I concentrations may be associated with an increased risk of ovarian cancer. A case-control study was nested within 3 prospective cohorts in New York (USA), Umeå (Sweden) and Milan (Italy). One hundred thirty-two women with primary invasive epithelial ovarian cancer diagnosed at least 1 year after blood donation were case subjects. For each case, 2 control subjects were selected, matching the case subject on cohort, menopausal status, age and date of recruitment (n = 263). Only women who did not use exogenous hormones at blood donation were included in the study. There was no association between IGF-I concentrations and ovarian cancer risk in the study group as a whole. In analyses restricted to subjects who had developed ovarian cancer at a young age (<55), circulating IGF-I was directly and strongly associated with ovarian cancer risk (OR = 4.97; 95% CI = 1.22-20.2 for the top vs. the bottom IGF-I tertile after adjustment for parity, BMI categories and smoking). There was no significant association of IGF binding protein-3 with ovarian cancer risk. We found a strong direct relationship between circulating IGF-I levels and risk of developing ovarian cancer before age 55. Additional, larger studies of this association are needed to provide more precise estimates of effect.

Validity of free testosterone and free estradiol determinations in serum samples from postmenopausal women by theoretical calculations

In this study, we validated measurements of free testosterone (fT) and free estradiol (fE(2)) concentrations calculated from total serum concentrations of testosterone (T), estradiol (E(2)), and sex hormone-binding globulin (SHBG), measured by direct, commercial radioimmunoassays, by comparison with reference measurements obtained by dialysis plus an in-house radioimmunoassay after extraction and chromatographic purification. The study was conducted in serum samples from 19 postmenopausal women who were part of an ongoing prospective cohort study. We also performed sensitivity analyses to examine the robustness of the theoretical calculations. Sensitivity analyses showed that in this population, competitive binding of dihydrotestosterone and total T could be ignored in the calculation of fE(2), and competitive binding by dihydrotestosterone does not need to be taken into account for calculation of fT. Furthermore, variations in albumin and SHBG concentrations had negligible effects on fT and fE(2) calculations. Values of fT and fE(2), calculated from total T and E(2) concentrations obtained by the same in-house radioimmunoassay used for the dialysis method, correlated highly with the measurements by dialysis (Pearson's coefficients of correlation above 0.97). When calculating fT and fE(2) using total T and total E(2) concentrations obtained by different direct radioimmunoassays, almost all kits gave good correlations with the reference method for fT (Pearson's r > 0.83), but only a few gave good correlations for fE(2) (Diagnostic System Laboratories and DiaSorin; r > 0.80). The direct radioimmunoassays giving the best correlation for fT and fE(2) with the dialysis method were those that best measured total concentrations of T and E(2). Furthermore, mean values of fT and fE(2) corresponded well to mean values by the reference method if SHBG measurements were also well calibrated. We conclude that in postmenopausal women, theoretical calculations are valid for the determination of fT and fE(2) concentrations and can give reliable estimation of cancer risk in epidemiological studies when the total concentrations of T, E(2), and SHBG are measured accurately.

Insulin-like growth factor II and colorectal cancer risk in women

Recently, a number of prospective studies showed evidence that the growth hormone/insulin-like growth factor I (IGF-I) axis may be important in the development of colorectal cancer. However, only a few studies have reported on the possible relationship of colorectal cancer risk with circulating levels of IGF-II, which are not growth hormone dependent and which do not vary with alterations in energy balance. In a case-control study of 102 cases and 200 matched controls nested within a cohort of 14,275 women in New York, we examined the relationship between colorectal cancer risk and prediagnostic serum levels of IGF-II. Conditional logistic regression analysis showed an odds ratio (OR) for colorectal cancer of 2.02 (95% confidence interval (CI): 0.83-4.93), comparing the upper to lower quintile of IGF-II. This association was slightly attenuated after excluding IGF-II measurements in serum samples taken within 1 year before case diagnosis (OR of 1.81; 95% CI: 0.71-4.64) and moderately attenuated after excluding IGF-II measurements in serum samples taken within 2 years before case diagnosis (OR of 1.47; 95% CI: 0.56-3.91). Adjustment for IGF-1, IGF binding protein (BP)-1, IGFBP-3, smoking, or body mass index did not substantially alter the association, whereas adjustment for IGFBP-2 moderately attenuated the relationship. Our results confirm those of three recent case-control studies, and collectively these results suggest a possible increase in colorectal cancer risk among subjects with comparatively elevated serum IGF-II. Mechanisms that might cause the increase in IGF-II levels are unknown but may include loss of parental imprinting of the IGF-II gene.

Aspirin and lung cancer in women

The association between aspirin use and lung cancer risk in women was examined in a case-control study nested in the New York University Women's Health Study, a large cohort in New York. Case subjects were all the 81 incident lung cancer cases who had provided information about aspirin use at enrollment and during the 1994-1996 follow up. Ten controls per case were randomly selected from among study participants who matched a case by age, menopausal status, and dates of enrollment and follow-up. Relative to no aspirin use, the odds ratio for lung cancer (all histological sub-types combined) among subjects who reported aspirin use three or more times per week for at least 6 months was 0.66 (95% confidence interval 0.34-1.28), after adjustment for smoking and education. A stronger inverse association was observed in analyses restricted to non-small cell lung cancer (adjusted odds ratio 0.39, 95% confidence interval 0.16-0.96). These results suggest that regular aspirin use might be inversely associated with risk of lung cancer in women, particularly the non-small cell sub-type.

Body mass index in relation to ovarian cancer: a multi-centre nested case-control study

The incidence of ovarian cancer is up to 10 times higher in Western countries than in rural Asia and Africa. One common consequence of a Western lifestyle is the development of excessive body weight and obesity. A multi-centre prospective study was conducted to investigate the association between body mass index (BMI) and ovarian cancer risk. A case-control study was nested within 3 prospective cohorts in New York (USA), Umeå (Sweden) and Milan (Italy). Information on anthropometry, demographic characteristics, medical history and lifestyle was obtained at the time of subjects' recruitment in each cohort. Women diagnosed with primary, invasive epithelial ovarian cancer from the 3 cohorts (n = 122) diagnosed 12 months or later after recruitment into the respective cohort served as case subjects. For each case subject, 2 control subjects that matched the case subject on cohort, menopausal status, age and date of recruitment were randomly identified. Data were analyzed by conditional logistic regression. There was an inverse association between BMI and ovarian cancer risk. For increasing quartiles of BMI above the lowest, the ORs were 0.62 (0.32-1.21), 0.59 (0.30-1.17) and 0.46 (0.23-0.92), p = 0.03. Analyses limited to women diagnosed 3 or more years after recruitment into the cohorts did not alter these findings. When obese women (BMI > 30) were compared to lean women (BMI < or = 23), the inverse association became stronger, with an OR of 0.38 (0.17-0.85), p < 0.02. There was some evidence of direct association of ovarian cancer with height, which was limited to cancers diagnosed before age 55. Our data suggest that increasing body weight may confer a protection against ovarian cancer.

Meat and dairy food consumption and breast cancer: a pooled analysis of cohort studies

BACKGROUND

More than 20 studies have investigated the relation between meat and dairy food consumption and breast cancer risk with conflicting results. Our objective was to evaluate the risk of breast cancer associated with meat and dairy food consumption and to assess whether non-dietary risk factors modify the relation.

METHODS

We combined the primary data from eight prospective cohort studies from North America and Western Europe with at least 200 incident breast cancer cases, assessment of usual food and nutrient intakes, and a validation study of the dietary assessment instrument. The pooled database included 351,041 women, 7379 of whom were diagnosed with invasive breast cancer during up to 15 years of follow-up.

RESULTS

We found no significant association between intakes of total meat, red meat, white meat, total dairy fluids, or total dairy solids and breast cancer risk. Categorical analyses suggested a J-shaped association for egg consumption where, compared to women who did not eat eggs, breast cancer risk was slightly decreased among women who consumed < 2 eggs per week but slightly increased among women who consumed > or = 1 egg per day.

CONCLUSIONS

We found no significant associations between intake of meat or dairy products and risk of breast cancer. An inconsistent relation between egg consumption and risk of breast cancer merits further investigation.

Aspirin and epithelial ovarian cancer

BACKGROUND

Epidemiological evidence suggests that chronic inflammation may influence ovarian carcinogenesis. The study objective was to examine the association between the commonly used anti-inflammatory drug aspirin and epithelial ovarian cancer.

METHODS

The authors conducted a case-control study based in the New York University Women's Health Study cohort enrolled between 1985 and 1991 in New York City. After a median follow-up period of 12 years, 68 incident cases of epithelial ovarian cancer were identified. Data about regular aspirin use were collected during the 1994-1996 follow-up questionnaire. Using a case-control study design, 10 controls per case were randomly selected among study participants who matched the case by age and menopausal status. Conditional logistic regression analysis was used to study the relationships between aspirin and epithelial ovarian cancer by generating odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Relative to no aspirin use, the OR for epithelial ovarian cancer among women who reported aspirin use three or more times per week for a period of at least 6 months was 0.60 (95% CI 0.26, 1.38), after adjustment for age at menarche, parity, oral contraceptive use, and first-degree family history of breast cancer before age 50. Among recent, within the previous 5 years, users of aspirin, the adjusted OR was 0.36 (95% CI 0.11, 1.18).

CONCLUSION

Although confidence intervals included unity, the observed risk estimates seem to be compatible with previous studies suggesting that regular aspirin use could be inversely associated with risk of epithelial ovarian cancer.

A cross-sectional study of IGF-I determinants in women

Evidence is accumulating that elevated circulating insulin-like growth factor I (IGF-I) is related to increased cancer risk. The identification of hormonal, reproductive and lifestyle characteristics influencing its synthesis and bioavailability is of particular interest. Data from 400 women, who served as controls in two case-control studies nested within the same prospective cohort study, were combined. IGF-I, IGF-binding proteins 1, 2 and 3 (IGFBP-1, -2, -3) and insulin were measured in serum samples from all subjects and cotinine in 186 samples. Age appears to be the most important determinant of total IGF-I levels in women. Anthropometric measures, such as body mass index (BMI) or waist-to-hip ratio (WHR) do not seem to influence total IGF-I concentrations in peripheral blood, but may modulate IGF-I bioavailability through insulin-dependent changes in IGFBP-1 and -2 concentrations. Age at menarche, phase of the menstrual cycle at blood draw, parity, menopause, past oral contraceptive or hormone replacement therapy use, and tobacco smoking do not appear to exert an independent effect on IGF-I and its binding proteins. There was some suggestion that regular physical activity may increase total IGF-I and that women with positive family history of breast cancer might have higher IGF-I levels than those without such diagnosis in their relatives.

Role of exogenous and endogenous hormones in endometrial cancer: review of the evidence and research perspectives

Endometrial carcinoma is the most common cancer of the female reproductive organs in the United States. International comparisons reveal that the incidence of endometrial cancer vary widely between different countries with the highest rates observed in North America and Northern Europe, intermediate rates in Eastern Europe and Latin America, and lowest rates in Asia and Africa. International variation in endometrial cancer rates may represent differences in the distribution of known risk factors, which include obesity, postmenopausal estrogen replacement, ovarian dysfunction, diabetes mellitus, infertility, nulliparity, and tamoxifen use. Most of the risk factors for endometrial cancer can be explained within the framework of the unopposed estrogen hypothesis, which proposes that exposure to estrogens unopposed by progesterone or synthetic progestins leads to increased mitotic activity of endometrial cells, increased number of DNA replication errors, and somatic mutations resulting in malignant phenotype. Although the impact of exogenous hormone replacement was intensively studied during the last two decades, less is known about the effects of endogenous hormones in endometrial cancer. A review of available experimental, clinical, and epidemiologic data suggests that in addition to estrogens, other endogenous hormones, including progesterone, androgens, gonadotropins, prolactin, insulin, and insulin-like growth factors, may play a role in the pathogenesis of different histopathologic types of endometrial cancer.

Reliability and validity of commercially available, direct radioimmunoassays for measurement of blood androgens and estrogens in postmenopausal women

In large-scale epidemiological studies on endogenous sex steroids and cancer risk, direct immunoassays of circulating hormone levels have the advantage of being fast and comparatively inexpensive while requiring only small sample volumes. On the other hand, indirect assays after organic extraction and chromatographic prepurification have the advantage of reducing specific interferences and matrix effects and hence are thought to have better validity. We compared direct assays of testosterone (T, six different assays), Delta4-androstenedione (A, four assays), estrone (E(1), one assay), and 17beta-estradiol (E(2), five assays) with measurements obtained by an indirect assay in a representative subset of 20 postmenopausal women who were part of a large prospective cohort study. Within-batch reproducibilities of the subject rankings by relative hormone levels were good (intraclass correlations >0.89) for all direct assays tested. Between batches, reproducibilities generally were also acceptable (r > 0.80) to good (r > 0.90) in terms of Pearson's correlations. The between-batch reproducibility in terms of intraclass correlations was systematically lower in terms of Pearson's correlations, however, because of between-batch variations in the absolute scale of measurements. The relative validity of direct versus indirect assays in terms of the subjects' ranking by relative hormone levels was also high for most of the kits tested for T, A, and E(1) (Pearson's correlations between 0.70 and 0.89) but was high for only two kits of five tested for E(2) (correlations of 0.86 and 0.84). On an absolute scale, mean measurement values were generally higher for direct assays than for the indirect assay and, for each hormone, varied substantially, depending on the kit used. Overall, the results of this study show that, with careful selection, commercial kits for direct radioimmunoassays of steroid hormones in postmenopausal serum can be found that may allow a reliable estimation of relative risks in epidemiological studies. However, standardization of the absolute scale of assays remains problematic.

Luteinizing hormone, its beta-subunit variant, and epithelial ovarian cancer: the gonadotropin hypothesis revisited

The gonadotropin hypothesis postulates that excessive gonadotropin stimulation results in increased proliferation and subsequent malignant transformation of ovarian epithelium. The authors evaluated this hypothesis by analyzing the association between serum levels of wild-type luteinizing hormone (LH) and ovarian cancer risk. They also examined the relation between a variant of LH containing two missense point mutations (Trp(8)Arg and Ile(15)Thr) in its beta-subunit and ovarian cancer risk. Fifty-eight cases of epithelial ovarian cancer and 116 controls matched on age, menopausal status, and date of blood donation were included in a case-control study nested within the New York University Women's Health Study, a prospective cohort enrolled between 1985 and 1991 in New York City. Wild-type serum levels and variant LH status were determined by immunofluorometric assays in which monoclonal antibodies specific for wild-type and variant LH were used. Compared with women in the lowest tertile of wild-type LH, women in the highest tertile had a lower risk of ovarian cancer, after adjustment for potential confounders (odds ratio = 0.42, 95% confidence interval: 0.09, 2.09). Women heterozygous for variant LH were not at increased risk (adjusted odds ratio = 0.95, 95% confidence interval: 0.27, 3.34). The results suggest that neither wild-type LH levels nor variant LH status is associated with increased risk of epithelial ovarian cancer.

Serum carotenoids and breast cancer

The consumption of vegetables and fruit may protect against many types of cancer, but research evidence is not compelling for breast cancer. Carotenoids are pigments that are present in most plants and have known antioxidant properties. Blood concentrations of carotenoids have been proposed as integrated biochemical markers of vegetable, fruit, and synthetic supplements consumed. In a case-control study (270 cases, 270 controls) nested within a cohort in New York during 1985-1994, the carotenoids lutein, zeaxanthin, beta-cryptoxanthin, lycopene, alpha-carotene, and beta-carotene were measured in archived serum samples using liquid chromatography. There was an evident increase in the risk of breast cancer for decreasing beta-carotene, lutein, alpha-carotene, and beta-cryptoxanthin. The risk of breast cancer approximately doubled among subjects with blood levels of beta-carotene at the lowest quartile, as compared with those at the highest quartile (odds ratio = 2.21; 95% confidence interval (CI): 1.29, 3.79). The risk associated with the other carotenoids was similar, varying between 2.08 (95% CI: 1.11, 3.90) for lutein and 1.68 (95% CI: 0.99, 2.86) for beta-cryptoxanthin. The odds ratio for the lower quartile of total carotenoids was 2.31 (95% CI: 1.35, 3.96). These observations offer evidence that a low intake of carotenoids, through poor diet and/or lack of vitamin supplementation, may be associated with increased risk of breast cancer and may have public health relevance for people with markedly low intakes.

Serum carotenoids as biomarkers of fruit and vegetable consumption in the New York Women's Health Study

OBJECTIVE

To investigate the usefulness of serum carotenoids as biomarkers of fruit and vegetable consumption.

DESIGN

: Reproducibility study on three repeat measurements of serum carotenoids. Correlation analysis of carotenoids and dietary food intake, and regression analysis of potential predictive parameters for serum carotenoid levels.

SETTING

New York, USA.

SUBJECT

: Women participating in the New York Women's Health Study, a prospective study of sex hormones, diet and breast cancer. Forty-eight women with three repeat blood samples and 302 women having a blood sample and a dietary history questionnaire (including 47 subjects from the reproducibility study).

RESULTS

Serum carotenoid concentrations were highly reproducible between one- and two-year repeat samples. Estimated fruit and vegetable consumption was positively correlated with serum carotenoid concentrations but correlation coefficients were low. Consumption of fruit was predictive for serum levels of beta-carotene, alpha-carotene and beta-cryptoxanthin, while vegetable consumption was predictive for serum beta-carotene, lutein, zeaxanthin and lycopene. Serum concentrations of cholesterol and triglycerides were predictive for serum carotenoids but adjustment for their levels had little or no influence on the correlation between fruit and vegetable consumption and serum carotenoid concentrations.

CONCLUSIONS

One single serum measurement of alpha-carotene, beta-carotene and lutein can accurately rank subjects according to their usual serum level. Serum concentrations, however, correlate only moderately with estimated dietary intake of fruits or vegetables and should therefore be used with caution as biomarkers of fruit and vegetable intake.

Types of dietary fat and breast cancer: a pooled analysis of cohort studies

Recently, there has been interest in whether intakes of specific types of fat are associated with breast cancer risk independently of other types of fat, but results have been inconsistent. We identified 8 prospective studies that met predefined criteria and analyzed their primary data using a standardized approach. Holding total energy intake constant, we calculated relative risks for increments of 5% of energy for each type of fat compared with an equivalent amount of energy from carbohydrates or from other types of fat. We combined study-specific relative risks using a random effects model. In the pooled database, 7,329 incident invasive breast cancer cases occurred among 351,821 women. The pooled relative risks (95% confidence intervals [CI]) for an increment of 5% of energy were 1.09 (1.00-1.19) for saturated, 0.93 (0.84-1.03) for monounsaturated and 1.05 (0.96-1.16) for polyunsaturated fat compared with equivalent energy intake from carbohydrates. For a 5% of energy increment, the relative risks were 1.18 (95% CI 0.99-1.42) for substituting saturated for monounsaturated fat, 0.98 (95% CI 0.85-1.12) for substituting saturated for polyunsaturated fat and 0.87 (95% CI 0.73-1.02) for substituting monounsaturated for polyunsaturated fat. No associations were observed for animal or vegetable fat intakes. These associations were not modified by menopausal status. These data are suggestive of only a weak positive association with substitution of saturated fat for carbohydrate consumption; none of the other types of fat examined was significantly associated with breast cancer risk relative to an equivalent reduction in carbohydrate consumption.

Postmenopausal endogenous oestrogens and risk of endometrial cancer: results of a prospective study

We assessed the association of postmenopausal serum levels of oestrogens and sex hormone-binding globulin (SHBG) with endometrial cancer risk in a case-control study nested within the NYU Women's Health Study cohort. Among 7054 women postmenopausal at enrolment, 57 cases of endometrial cancer were diagnosed a median of 5.5 years after blood donation. Each case was compared to 4 controls matched on age, menopausal status at enrolment, and serum storage duration. Endometrial cancer risk increased with higher levels of oestradiol (odds ratio = 2.4 in highest vs lowest tertile, P for trend = 0.02), percent free oestradiol (OR = 3.5, P< 0.001), and oestrone (OR = 3.9, P< 0.001). Risk decreased with higher levels of percent SHBG-bound oestradiol (OR = 0.43, P = 0.03) and SHBG (OR = 0.39, P = 0.01). Trends remained in the same directions after adjusting for height and body mass index. A positive association of body mass index with risk was substantially reduced after adjusting for oestrone level. Our results indicate that risk of endometrial cancer increases with increasing postmenopausal oestrogen levels but do not provide strong support for a role of body mass index independent of its effect on oestrogen levels.