Levonorgestrel-releasing intrauterine system use is associated with a decreased risk of ovarian and endometrial cancer, without increased risk of breast cancer. Results from the NOWAC Study.

OBJECTIVE: Women with ovarian cancer have poor survival rates, which have proven difficult to improve; therefore primary prevention is important. The levonorgestrel-releasing intrauterine system (LNG-IUS) prevents endometrial cancer, and recent studies suggested that it may also prevent ovarian cancer, but with a concurrent increased risk of breast cancer. We compared adjusted risks of ovarian, endometrial, and breast cancer in ever users and never users of LNG-IUS. METHODS: Our study cohort consisted of 104,318 women from the Norwegian Women and Cancer Study, 9144 of whom were ever users and 95,174 of whom were never users of LNG-IUS. Exposure information was taken from self-administered questionnaires, and cancer cases were identified through linkage to the Cancer Registry of Norway. Relative risks (RRs) with 95% confidence intervals (CIs) were estimated with Poisson regression using robust error estimates. RESULTS: Median age at inclusion was 52years and mean follow-up time was 12.5 (standard deviation 3.7) years, for a total of 1,305,435 person-years. Among ever users of LNG-IUS there were 18 cases of epithelial ovarian cancer, 15 cases of endometrial cancer, and 297 cases of breast cancer. When ever users were compared to never users of LNG-IUS, the multivariable RR of ovarian, endometrial, and breast cancer was 0.53 (95% CI: 0.32, 0.88), 0.22 (0.13, 0.40), and 1.03 (0.91, 1.17), respectively. CONCLUSION: In this population-based prospective cohort study, ever users of LNG-IUS had a strongly reduced risk of ovarian and endometrial cancer compared to never users, with no increased risk of breast cancer.

Does an epidemiological comparison support a common cellular lineage for similar subtypes of postmenopausal uterine and ovarian carcinoma? The Norwegian Women and Cancer Study.

Uterine and ovarian carcinomas have the same major histological subtypes, but whether they originate from the same cell types is a matter of ongoing debate. Uterine and ovarian endometrioid and clear cell carcinoma (ECC) and uterine and ovarian serous carcinoma (SC) may originate in the same location, or share a common lineage of differentiation. Epidemiologically, a common cellular lineage should be reflected in similar risk associations, and we explored the similarity of uterine and ovarian ECC and uterine and ovarian SC. We included 146,316 postmenopausal participants from the Norwegian Women and Cancer Study. Exposure information was taken from self-administered questionnaires, and cancer cases were identified through linkage to the Cancer Registry of Norway. Hazard ratios with 95% confidence intervals for uterine and ovarian carcinoma and their subtypes were calculated using multivariable Cox regression models, and a Wald test was used to check for heterogeneity. During 1.6 million person-years, 1,006 uterine and 601 ovarian carcinomas were identified. Parity, total menstrual lifespan, body mass index and smoking were differentially associated with total uterine and total ovarian carcinoma (pheterogeneity  = 0.041, 0.027, <0.001 and 0.001, respectively). The corresponding associations for uterine and ovarian ECC did not differ significantly (pheterogeneity  > 0.05). Smoking was differentially associated with uterine and ovarian SC (pheterogeneity  = 0.021). Our epidemiological analyses do not contradict a common differentiation lineage for uterine and ovarian ECC. Uterine and ovarian SC are less likely to be of a common lineage of differentiation, based on their difference in risk associated with smoking.

Physical activity and risk of endometrial cancer in the Norwegian Women and Cancer (NOWAC) study.

Few studies have investigated the association between endometrial cancer and physical activity (PA) using repeated measures of PA and different subtypes of endometrial cancer. We aimed to investigate the association between endometrial cancer and PA level at two points in time in women with different body mass index (BMI) profiles, and to calculate the population attributable fraction (PAF) of endometrial cancer for low PA levels. We included 82,759 women with complete information on PA at baseline in the Norwegian Women and Cancer Study; 52,370 had follow-up information on PA. 687 endometrial cancer cases were identified. Multivariate cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI). The PAF indicated the proportion of endometrial cancer that could be avoided in the population if these women had a higher PA level. There was a statistically significant association between low PA levels at baseline and follow-up and endometrial cancer risk, with a dose-response trend (lowest PA level: HR = 1.60, 95% CI 1.16-2.20; highest PA level: HR = 0.73, 95% CI 0.45-1.16 compared to the median). Analyses that included follow-up measurements yielded similar results. 21.9% (95% CI 7.1-34.3) of endometrial cancers could be avoided if women with low PA levels (≤ 4 in a 1-10 degree self reported PA scale) increased their PA levels to 5-10. We found an inverse dose-response association between PA and endometrial cancer, independent of BMI. In this nationally representative cohort, 21.9% of endometrial cancers could potentially be avoided if PA levels increased to higher PA levels.

Coffee consumption and the risk of malignant melanoma in the Norwegian Women and Cancer (NOWAC) Study.

BACKGROUND: Coffee contains biologically-active substances that suppress carcinogenesis in vivo, and coffee consumption has been associated with a lower risk of malignant melanoma. We studied the impact of total coffee consumption and of different brewing methods on the incidence of malignant melanoma in a prospective cohort of Norwegian women. METHODS: We had baseline information on total coffee consumption and consumption of filtered, instant, and boiled coffee from self-administered questionnaires for 104,080 women in the Norwegian Women and Cancer (NOWAC) Study. We also had follow-up information collected 6-8 years after baseline. Multiple imputation was used to deal with missing data, and multivariable Cox regression models were used to calculate hazard ratios (HR) for malignant melanoma by consumption category of total, filtered, instant, and boiled coffee. RESULTS: During 1.7 million person-years of follow-up, 762 cases of malignant melanoma were diagnosed. Compared to light consumers of filtered coffee (≤1 cup/day), we found a statistically significant inverse association with low-moderate consumption (>1-3 cups/day, HR = 0.80; 95 % confidence interval [CI] 0.66-0.98) and high-moderate consumption of filtered coffee (>3-5 cups/day, HR = 0.77; 95 % CI 0.61-0.97) and melanoma risk (p trend = 0.02). We did not find a statistically significant association between total, instant, or boiled coffee consumption and the risk of malignant melanoma in any of the consumption categories. CONCLUSIONS: The data from the NOWAC Study indicate that a moderate intake of filtered coffee could reduce the risk of malignant melanoma.

Reproductive factors and epithelial ovarian cancer survival in the EPIC cohort study.

BACKGROUND: Reproductive factors influence the risk of developing epithelial ovarian cancer (EOC), but little is known about their association with survival. We tested whether prediagnostic reproductive factors influenced EOC-specific survival among 1025 invasive EOC cases identified in the European Prospective Investigation into Cancer and Nutrition (EPIC) study, which included 521,330 total participants (approximately 370,000 women) aged 25-70 years at recruitment from 1992 to 2000. METHODS: Information on reproductive characteristics was collected at recruitment. Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), and multivariable models were adjusted for age and year of diagnosis, body mass index, tumour stage, smoking status and stratified by study centre. RESULTS: After a mean follow-up of 3.6 years (±3.2 s.d.) following EOC diagnosis, 511 (49.9%) of the 1025 women died from EOC. We observed a suggestive survival advantage in menopausal hormone therapy (MHT) users (ever vs never use, HR=0.80, 95% CI=0.62-1.03) and a significant survival benefit in long-term MHT users (⩾5 years use vs never use, HR=0.70, 95% CI=0.50-0.99, P(trend)=0.04). We observed similar results for MHT use when restricting to serous cases. Other reproductive factors, including parity, breastfeeding, oral contraceptive use and age at menarche or menopause, were not associated with EOC-specific mortality risk. CONCLUSIONS: Further studies are warranted to investigate the possible improvement in EOC survival in MHT users.

The blood transcriptome prior to ovarian cancer diagnosis: A case-control study in the NOWAC postgenome cohort.

Epithelial ovarian cancer (EOC) has a 5-year relative survival of 50%, partly because markers of early-stage disease are not available in current clinical diagnostics. The aim of the present study was to investigate whether EOC is associated with transcriptional profiles in blood collected up to 7 years before diagnosis. For this, we used RNA-stabilized whole blood, which contains circulating immune cells, from a sample of EOC cases from the population-based Norwegian Women and Cancer (NOWAC) postgenome cohort. We explored case-control differences in gene expression in all EOC (66 case-control pairs), as well as associations between gene expression and metastatic EOC (56 pairs), serous EOC (45 pairs, 44 of which were metastatic), and interval from blood sample collection to diagnosis (≤3 or >3 years; 34 and 31 pairs, respectively). Lastly, we assessed differential expression of genes associated with EOC in published functional genomics studies that used blood samples collected from newly diagnosed women. After adjustment for multiple testing, this nested case-control study revealed no significant case-control differences in gene expression in all EOC (false discovery rate q>0.96). With the exception of a few probes, the log2 fold change values obtained in gene-wise linear models were below ±0.2. P-values were lowest in analyses of metastatic EOC (80% of which were serous EOC). No common transcriptional profile was indicated by interval to diagnosis; when comparing the 100 genes with the lowest p-values in gene-wise tests in samples collected ≤3 and >3 years before EOC diagnosis, no overlap in these genes was observed. Among 86 genes linked to ovarian cancer in previous publications, our data contained expression values for 42, and of these, tests of LIME1, GPR162, STAB1, and SKAP1, resulted in unadjusted p<0.05. Although limited by sample size, our findings indicated less variation in blood gene expression between women with similar tumor characteristics.

High lactose whey cheese consumption and risk of colorectal cancer - The Norwegian Women and Cancer Study.

The incidence of colorectal cancer (CRC) has increased among Norwegian women, and is among the highest in the world. In order to understand this increase, country specific dietary exposures have been investigated. The aim of this study was to quantify the association between consumption of brown cheese, a common bread topping in Norway, and colorectal, colon, and rectal cancer in the prospective Norwegian Women and Cancer (NOWAC) Study. Data on brown cheese consumption and adjustment factors was available for 82 527 women. During a mean of 14.6 years of follow-up (1.2 million person-years), there were 1360 cases of colorectal cancer (907 colon; 453 rectal). Multivariable Cox proportional hazards models were used to calculate hazard ratios (HR) with 95% confidence intervals (CI) for colorectal, colon, and rectal cancer sites. We modelled restricted cubic splines with 4 knots, to assess a possible non-linear relationship between brown cheese intake and the investigated cancer sites. In the age-adjusted model, consumption of more than 2 slices (>16 grams) of brown cheese per day was associated with 13% reduced risk of colon cancer (95% CI 4%-21%) compared to women who did not consume brown cheese. The multivariable-adjusted model, however, showed no association between brown cheese consumption and the risk of colorectal, colon, or rectal cancer (colorectal: HR = 0.93, 95% CI 0.76-1.13, p-trend 0.37; colon: HR = 0.83, 95% CI 0.65-1.06; p-trend = 0.10; rectal: HR = 1.16, 95% CI 0.84-1.1.61, p-trend = 0.41). In this large, prospective cohort study of women, consumption of brown cheese was suggestively protective against colon cancer. However, adjustment attenuated the inverse risk association. Brown cheese consumption was not associated with rectal cancer, or colorectal cancer overall.

Correlates of circulating ovarian cancer early detection markers and their contribution to discrimination of early detection models: results from the EPIC cohort.

BACKGROUND: Ovarian cancer early detection markers CA125, CA15.3, HE4, and CA72.4 vary between healthy women, limiting their utility for screening. METHODS: We evaluated cross-sectional relationships between lifestyle and reproductive factors and these markers among controls (n = 1910) from a nested case-control study in the European Prospective Investigation into Cancer and Nutrition (EPIC). Improvements in discrimination of prediction models adjusting for correlates of the markers were evaluated among postmenopausal women in the nested case-control study (n = 590 cases). Generalized linear models were used to calculate geometric means of CA125, CA15.3, and HE4. CA72.4 above vs. below limit of detection was evaluated using logistic regression. Early detection prediction was modeled using conditional logistic regression. RESULTS: CA125 concentrations were lower, and CA15.3 higher, in post- vs. premenopausal women (p ≤ 0.02). Among postmenopausal women, CA125 was higher among women with higher parity and older age at menopause (ptrend ≤ 0.02), but lower among women reporting oophorectomy, hysterectomy, ever use of estrogen-only hormone therapy, or current smoking (p < 0.01). CA15.3 concentrations were higher among heavier women and in former smokers (p ≤ 0.03). HE4 was higher with older age at blood collection and in current smokers, and inversely associated with OC use duration, parity, and older age at menopause (≤ 0.02). No associations were observed with CA72.4. Adjusting for correlates of the markers in prediction models did not improve the discrimination. CONCLUSIONS: This study provides insights into sources of variation in ovarian cancer early detection markers in healthy women and informs about the utility of individualizing marker cutpoints based on epidemiologic factors.

Epithelial ovarian cancer subtypes attributable to smoking in the Norwegian Women and Cancer Study, 2012.

Among European women, ovarian cancer is the fifth most common cancer. Smoking is an established risk factor for mucinous tumors. We estimated the impact of smoking in Norwegian women using population attributable fractions (PAFs) of epithelial ovarian cancer (EOC), by invasiveness and by histological subtypes in the Norwegian Women and Cancer Study with an average of 13.2 years of follow-up. During >2 million person-years, a total of 915 incident EOC cases, of which 667 (73%) invasive and 248 (27%) borderline, were identified among 154,234 women aged 34-70 years at enrolment. Compared with never smokers, current smokers had a nonstatistically significant increased risk of mucinous tumors (hazard ratio [HR] = 1.67 [95% confidence interval, (CI), 0.96-2.96]) and more than twice statistically significant risk of borderline mucinous tumors (HR = 2.17 [95% CI, 1.06-4.45]). The corresponding PAF estimates were 16.5% for mucinous and 25% for borderline mucinous. We found that among middle-aged women, one in six mucinous tumors and one in four borderline mucinous tumors could have been prevented if women did not smoke.

Nutrient-wide association study of 57 foods/nutrients and epithelial ovarian cancer in the European Prospective Investigation into Cancer and Nutrition study and the Netherlands Cohort Study.

BACKGROUND: Studies of the role of dietary factors in epithelial ovarian cancer (EOC) development have been limited, and no specific dietary factors have been consistently associated with EOC risk. OBJECTIVE: We used a nutrient-wide association study approach to systematically test the association between dietary factors and invasive EOC risk while accounting for multiple hypothesis testing by using the false discovery rate and evaluated the findings in an independent cohort. DESIGN: We assessed dietary intake amounts of 28 foods/food groups and 29 nutrients estimated by using dietary questionnaires in the EPIC (European Prospective Investigation into Cancer and Nutrition) study (n = 1095 cases). We selected 4 foods/nutrients that were statistically significantly associated with EOC risk when comparing the extreme quartiles of intake in the EPIC study (false discovery rate = 0.43) and evaluated these factors in the NLCS (Netherlands Cohort Study; n = 383 cases). Cox regression models were used to estimate HRs and 95% CIs. RESULTS: None of the 4 dietary factors that were associated with EOC risk in the EPIC study (cholesterol, polyunsaturated and saturated fat, and bananas) were statistically significantly associated with EOC risk in the NLCS; however, in meta-analysis of the EPIC study and the NLCS, we observed a higher risk of EOC with a high than with a low intake of saturated fat (quartile 4 compared with quartile 1; overall HR: 1.21; 95% CI: 1.04, 1.41). CONCLUSION: In the meta-analysis of both studies, there was a higher risk of EOC with a high than with a low intake of saturated fat.

Kvik: three-tier data exploration tools for flexible analysis of genomic data in epidemiological studies.

Kvik is an open-source framework that we developed for explorative analysis of functional genomics data from large epidemiological studies. Creating such studies requires a significant amount of time and resources. It is therefore usual to reuse the data from one study for several research projects. Often each project requires implementing new analysis code, integration with specific knowledge bases, and specific visualizations. Although existing data exploration tools are available for single study data exploration, no tool provides all the required functionality for multistudy data exploration. We have therefore used the Kvik framework to develop Kvik Pathways, an application for exploring gene expression data in the context of biological pathways. We have used Kvik Pathways to explore data from both a cross-sectional study design and a case-control study within the Norwegian Women and Cancer (NOWAC) cohort. Kvik Pathways follows the three-tier architecture in web applications using a powerful back-end for statistical analyses and retrieval of metadata.In this note, we describe how we used the Kvik framework to develop the Kvik Pathways application. Kvik Pathways was used by our team of epidemiologists toexplore gene expression data from healthy women with high and low plasma ratios of essential fatty acids.

Leukocyte telomere length in relation to pancreatic cancer risk: a prospective study.

BACKGROUND: Several studies have examined leukocyte telomere length (LTL) as a possible predictor for cancer at various organ sites. The hypothesis originally motivating many of these studies was that shorter telomeres would be associated with an increase in cancer risk; the results of epidemiologic studies have been inconsistent, however, and suggested positive, negative, or null associations. Two studies have addressed the association of LTL in relation to pancreatic cancer risk and the results are contrasting. METHODS: We measured LTL in a prospective study of 331 pancreatic cancer cases and 331 controls in the context of the European Prospective Investigation into Cancer and Nutrition (EPIC). RESULTS: We observed that the mean LTL was higher in cases (0.59 ± 0.20) than in controls (0.57 ± 0.17), although this difference was not statistically significant (P = 0.07), and a basic logistic regression model showed no association of LTL with pancreas cancer risk. When adjusting for levels of HbA1c and C-peptide, however, there was a weakly positive association between longer LTL and pancreatic cancer risk [OR, 1.13; 95% confidence interval (CI), 1.01-1.27]. Additional analyses by cubic spline regression suggested a possible nonlinear relationship between LTL and pancreatic cancer risk (P = 0.022), with a statistically nonsignificant increase in risk at very low LTL, as well as a significant increase at high LTL. CONCLUSION: Taken together, the results from our study do not support LTL as a uniform and strong predictor of pancreatic cancer. IMPACT: The results of this article can provide insights into telomere dynamics and highlight the complex relationship between LTL and pancreatic cancer risk.