Robien, Kim

Nitrate and nitrite are precursors in the endogenous formation of N‐nitroso compounds (NOC), potential human carcinogens. We evaluated the association of nitrate and nitrite ingestion with postmenopausal ovarian cancer risk in the Iowa Women's Health Study. Among 28,555 postmenopausal women, we identified 315 incident epithelial ovarian cancers from 1986 to 2010. Dietary nitrate and nitrite intakes were assessed at baseline using food frequency questionnaire data. Drinking water source at home was obtained in a 1989 follow‐up survey. Nitrate‐nitrogen (NO3‐N) and total trihalomethane (TTHM) levels for Iowa public water utilities were linked to residences and average levels were computed based on each woman's duration at the residence. We computed multivariable‐adjusted hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazards regression. We tested interactions of nitrate with TTHMs and dietary factors known to influence NOC formation. Ovarian cancer risk was 2.03 times higher (CI = 1.22–3.38, ptrend = 0.003) in the highest quartile (≥2.98 mg/L) compared with the lowest quartile (≤0.47 mg/L; reference) of NO3‐N in public water, regardless of TTHM levels. Risk among private well users was also elevated (HR = 1.53, CI = 0.93–2.54) compared with the same reference group. Associations were stronger when vitamin C intake was <median (pinteraction = 0.01 and 0.33 for private well and public supplies, respectively). Dietary nitrate was inversely associated with ovarian cancer risk (ptrend = 0.02); whereas, dietary nitrite from processed meats was positively associated with the risk (ptrend = 0.04). Our findings indicate that high nitrate levels in public drinking water and private well use may increase ovarian cancer risk among postmenopausal women.

Abstract Background: With over 13 million cancer survivors in the United States today, second cancers are of rapidly growing importance. However, data on nontreatment risk factors for second cancers are sparse. We explored the feasibility of pooling data from cohort studies of cancer incidence to investigate second cancer etiology. Methods: We combined data from five prospective studies including more than 800,000 individuals. We compared study designs and populations; evaluated availability of and ability to harmonize risk factor data; compared incidence and survival for common first primary malignancies and incidence of second primary malignancies; and estimated sample size requirements. Results: Overall, 96,513 incident, first primary malignancies were diagnosed during 1985 to 2009. Incidence rates and survival following the first primary varied among the cohorts, but most of the heterogeneity could be explained by characteristics of the study populations (age, sex, smoking, and screening rates). A total of 7,890 second primary cancers (excluding original primary site) were identified, yielding sufficient statistical power (≥80%) for detecting modest associations with risk of all second cancers among survivors of common first primary malignancies (e.g., colorectal cancer); however, there were insufficient events for studying survivors of rarer cancers or identifying risk factors for specific second cancers. Conclusions: Pooling data from cohort studies to investigate nontreatment risk factors for second primary cancers seems feasible but there are important methodologic issues—some of which are barriers to specific research questions—that require special attention. Impact: Increased understanding of nontreatment risk factors for second cancers will provide valuable prevention and surveillance information. Cancer Epidemiol Biomarkers Prev; 23(8); 1598–608. ©2014 AACR.

Abstract Background: Sugar-sweetened beverage (SSB) intake has been associated with an increased risk of obesity and type II diabetes. However, its association with endometrial cancer is unclear. Methods: We evaluated dietary intake of SSB, fruit juice, sugar-free beverages, sweets/baked goods, starch, and sugars among 23,039 postmenopausal women in the Iowa Women's Health Study. Incident estrogen-dependent type I and estrogen-independent type II endometrial cancers were identified via linkage with the Surveillance Epidemiology and End Results Registry. Risks of type I and type II endometrial cancers were separately compared by energy-adjusted dietary intake in Cox proportional hazards regression models. Results: From 1986 to 2010, 506 type I and 89 type II incident endometrial cancers were identified. An increased risk of type I endometrial cancer was observed with increasing SSB intake after adjustment for body mass index (BMI) and other cofounders (Ptrend = 0.0005). Compared with nondrinkers of SSB, the risk was 78% higher [95% confidence intervals (CI), 1.32–2.40] among women in the highest quintile of SSB intake. The observed association was not modified by BMI, physical activity, history of diabetes, or cigarette smoking. Higher risk of type I endometrial cancer was also observed with higher intake of sugars. None of the dietary items included in the analysis was associated with type II endometrial cancer risk. Conclusion: Higher intake of SSB and sugars was associated with an increased risk of type I, but not type II, endometrial cancer. Impact: SSB intake may be a risk factor for type I endometrial cancer regardless of other lifestyle factors. Cancer Epidemiol Biomarkers Prev; 22(12); 2384–94. ©2013 AACR.

Abstract Some studies show that childbearing at older age is associated with lower risk of endometrial cancer, but whether the association is independent of number of children or other factors still requires clarification. We pooled individual-level data from epidemiologic studies in the Epidemiology of Endometrial Cancer Consortium (E2C2). Data on age at last birth and/or last pregnancy were available from 14 studies: 11 case-control studies and 3 cohort studies; the latter were analyzed using a nested case-control design. A total of 9,613 endometrial cancer cases and 17,112 controls were included in the analysis. The majority of women were White (82%) and older than 55 years (69%). We estimated the effects of age at last birth using data from 12 studies and age at last pregnancy using data from 10 studies on the risk of endometrial cancer by calculating odds ratios (OR) and 95% confidence intervals (95% CI) using logistic regression models. Potential confounders included in the analysis were race, body mass index, parity, age at menarche, age at first birth, oral contraceptive use, postmenopausal hormone use, smoking status, and report of diabetes. After adjusting for potential confounders, a reduction in endometrial cancer risk was observed in women with increasing age at last birth (P trend &lt;0.0001) and age at last pregnancy (P trend &lt;0.0001). The OR per five-year increase in age at last birth and age at last pregnancy was 0.90 (95%CI: 0.86, 0.94) and 0.91 (95% CI: 0.87, 0.95), respectively. Women who had their last child at an age &gt;40 years were at a 34% decreased risk compared with women who had their last child at an age &lt;25 years (95% CI: 0.52, 0.82). Compared to women with age at last pregnancy &lt;25 years, those with age at last pregnancy &gt;40 years had a 30% decreased risk of endometrial cancer (95%CI: 0.57, 0.86). Inverse associations were observed for Whites and Asians in race-specific analysis and also in analysis restricted to women with at least 2 births. In this large pooled analysis, we show that late age at last birth or last pregnancy is a strong and independent protective factor for endometrial cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1900. doi:10.1158/1538-7445.AM2011-1900

Abstract Background: Ingested nitrate can form N-nitroso compounds endogenously, which may lead to DNA adducts and activating mutations in oncogenes. However, previous studies have reported null or inverse associations between dietary nitrate intake and cancer risk, while nitrate intake from drinking water has shown null or positive associations with cancer risk. These associations may be confounded by protective effects of dietary folate, which provides methyl groups for nucleotide synthesis, and thus plays a vital role in the DNA repair system. In a small case-control study, an increased risk of breast cancer was observed among individuals with high dietary nitrate relative to folate intake. We therefore evaluated interaction of total folate with nitrate intake from diet and drinking water on breast cancer risk in the Iowa Women's Health Study (IWHS). Methods: The IWHS is a prospective cohort study of cancer among 41,836 women in Iowa, initiated in 1986. Dietary intake was assessed at study baseline using a food frequency questionnaire (FFQ). Nitrate intake from foods and total folate intake from foods and dietary supplements were computed using consumption frequencies collected by the FFQ. Nitrate intake from drinking water was assessed using a historical analytical database on Iowa municipal water supplies in 15,151 women using municipal water supply. We evaluated the interaction of nitrate and total folate intake with breast cancer risk using Cox proportional hazard regression modeling, adjusting for potential confounders (age, body mass index, waist-hip-ratio, education, smoking, family history of breast cancer, age at menopause, age at first live birth, estrogen use, total energy intake, and intake of vitamin C and E and flavonoids). Results: After baseline exclusions (history of cancer at baseline, previous mastectomy or partial breast resection, implausible energy intake, or ≥30 missing responses on the FFQ), there were 34,388 postmenopausal women in the analytic cohort. Through 2008, 2,875 incident breast cancer cases were identified. Nitrate intake from diet or drinking water was not associated with breast cancer risk. After stratification by total folate intake, high dietary nitrate intake (&gt;106.1 mg/day) was associated with a marginally decreased risk of breast cancer compared to those with low nitrate intake (≤106.1 mg/day) (HR=0.90, 95% confidence interval=0.81–1.00) only among women with folate intake &lt;400 μg/day (p for interaction = 0.65). There was no interaction of nitrate intake from drinking water and total folate intake on breast cancer risk. Conclusions: Our findings do not support the previously reported increased risk of breast cancer risk among individuals with high dietary nitrate and low folate intake. The inverse association between nitrate intake and breast cancer risk observed among women with low folate intake in the present study may be attributed to residual confounding due to high correlation among intakes of nitrate, folate and antioxidants. Citation Information: Cancer Prev Res 2011;4(10 Suppl):A86.