Cancer Case-control Study Research Articles

Chronic obstructive pulmonary disease among lung cancer-free smokers: The importance of healthy controls.

The prevalence of chronic obstructive pulmonary disease (COPD) in smokers enrolled as "healthy" controls in studies is 10-50%. The COPD status of ideal smoker populations for lung cancer case-control studies should be checked via spirometry; however, this is often not feasible, because no medical indications exist for asymptomatic smokers to undergo spirometry prior to study enrollment. Therefore, there is an unmet need for robust, cost effective assays for identifying undiagnosed lung disease among asymptomatic smokers. Such assays would help excluding unhealthy smokers from lung cancer case-control studies. We used the cytokinesis-blocked micronucleus (CBMN) assay (a measure of genetic instability) to identify undiagnosed lung disease among asymptomatic smokers. We used a convenience population from an on-going lung cancer case-control study including smokers with lung cancer (n = 454), smoker controls (n = 797), and a self-reported COPD (n = 200) contingent within the smoker controls. Significant differences for all CBMN endpoints were observed when comparing lung cancer to All controls (which included COPD) and Healthy controls (with no COPD). The risk ratio (RR) was increased in the COPD group vs. Healthy controls for nuclear buds (RR 1.28, 95% confidence interval 1.01-1.62), and marginally increased for micronuclei (RR 1.06, 0.98-1.89) and nucleoplasmic bridges (RR 1.07, 0.97-1.15). These findings highlight the importance of using truly healthy controls in studies geared toward assessment of lung cancer risk. Using genetic instability biomarkers would facilitate the identification of smokers susceptible to tobacco smoke carcinogens and therefore predisposed to either disease.

Abstract A01: Mechanisms of breast cancer risk in shift workers: Epigenetic changes in the circadian pathway

Abstract Occupational factors such as shiftwork and especially night work that involves disruption of the circadian rhythm can increase breast cancer risk. Circadian disruption may also affect epigenetic factors such as 5-methyl cytosine methylation in DNA. DNA hypermethylation generally is associated with increased cancer risk, if it occurs in tumor suppressor genes. Some of the circadian genes are known to function as tumor suppressor genes. DNA methylation in cirdavdian genes and its association with breast cancer risk in shiftworkers is little investigated and the limited available data are inconclusive. We here investigated DNA methyalation at 5-meC sites in the promoter regions of core circadian and melatonin receptor genes as a potential mechanism for night work-related breast cancer risk. A nested breast cancer case-control study of nurses working night shifts comprising of seven-hundred breast cancer cases and matched controls was conducted. Methylation at 5-meC sites in a number of core circadian and melatonin receptor genes was in DNA from sputum samples obtained from cases and controls. Changes in methylation status of the 5-meC in DNA (methylation index) and the odds of breast cancer associated with DNA methylation was calculated in relation to the duration and intensity of night shiftwork. We demonstrate that generally the methylation of 5-meC is low for all the genes that were analyzed. However, we will present analyses of the effects of work schedules and duration, as number of consecutive night shifts, on epigenetic changes. The hypothesis is that increased breast cancer risk in workers with long periods of consecutive night shifts may be associated with changes in methylation status of the genes regulation the circadian rhythm. Citation Format: Shan Zienolddiny. Mechanisms of breast cancer risk in shift workers: Epigenetic changes in the circadian pathway [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr A01.

Analysis of case-control data with interacting misclassified covariates

Case-control studies are important and useful methods for studying health outcomes and many methods have been developed for analyzing case-control data. Those methods, however, are vulnerable to mismeasurement of variables; biased results are often produced if such a feature is ignored. In this paper, we develop an inference method for handling case-control data with interacting misclassified covariates. We use the prospective logistic regression model to feature the development of the disease. To characterize the misclassification process, we consider a practical situation where replicated measurements of error-prone covariates are available. Our work is motivated in part by a breast cancer case-control study where two binary covariates are subject to misclassification. Extensions to other settings are outlined.

Red and processed meat consumption and colorectal cancer risk: a systematic review and meta-analysis.

The associations between red and processed meat consumption and the risk of colorectal cancer types have not been conclusively defined. We performed a systematic review and meta-analysis to analyze these associations. We searched PubMed and EMBASE to identify studies published from inception through September 2016. Dose-response, subgroup and subtype analyses of colorectal cancer (colon cancer, proximal colon cancer, distal colon cancer and rectal cancer) were performed. We ultimately selected 60 eligible studies. Positive associations were observed for colorectal cancer in case-control studies (red meat, P<0.01; processed meat, P<0.01) and cohort studies (red meat, P<0.01; processed meat, P<0.01). However, subtype analyses yielded null results for distal colon cancer in case-control studies (P=0.41) and cohort studies (P=0.18) for red meat and null results for proximal colon cancer in case-control studies (P=0.13) and cohort studies (P=0.39) for processed meat. Additionally, although the results of case-control studies were positive (red meat, P<0.01; processed meat, P=0.04) for rectal cancer, there were no positive associations between red (P=0.34) and processed meat (P=0.06) consumption and the risk in cohort studies. In a systematic review and meta-analysis, we found consumption of red and processed meat was associated with the risk of overall colorectal cancer but not rectal cancer. Additionally, there were no associations between the consumption of red meat and distal colon cancer risk and between the consumption of processed meat and proximal colon cancer risk.

Development of a population-based cancer case-control study in southern china.

With its population of over 1.3 billion persons, China offers abundant opportunities to discover causes of disease. However, few rigorous population-based case-control studies have as yet been conducted in mainland China. We conducted a population-based case-control study of nasopharyngeal carcinoma in Guangdong Province and Guangxi Autonomous Region. We collected questionnaires and biospecimens from incident cases recruited between March 2010 and December 2013, and population-based controls between November 2010 and November 2014. Preparatory activities prior to subject enrollment required approximately 18 months. We enrolled a total of 2554 NPC cases and 2648 controls. Among all identified cases, 83.8% participated. For the participating cases, the median time between diagnosis and interview was 2 days. Among all contacted controls, 82.7% participated. From the enrolled cases, we collected 2518 blood specimens (provided by 98.6% of eligible cases), 2350 saliva specimens (92.0%), 2514 hair specimens (98.4%), and 2507 toenail/fingernail specimens (98.2%). From the enrolled controls, we collected 2416 blood specimens (91.2%), 2505 saliva specimens (94.6%), 2517 hair specimens (95.1%), and 2514 toenail/fingernail specimens (94.9%). We demonstrate that population-based epidemiologic research can successfully be conducted in southern China. The study protocols, databases, and biobank will serve as an extraordinarily valuable resource for testing future etiologic hypotheses.

Mechanisms of breast cancer risk in shift workers: association of telomere shortening with the duration and intensity of night work.

Occupational factors such as shiftwork and especially night work that involves disruption of the circadian rhythm may contribute to increased breast cancer risk. Circadian disruption may also affect telomere length (TL). While short TL generally is associated with increased cancer risk, its association with breast cancer risk is inconclusive. We suggest that working schedules might be an important factor in assessment of effects of TL on breast cancer risk. Moreover, telomere shortening might be a potential mechanism for night work‐related breast cancer. In this study, effects of shift work on TL and its association with breast cancer risk were investigated in a nested breast cancer case–control study of Norwegian nurses. TL was assessed by qPCR in DNA from 563 breast cancer patients and 619 controls. Here, we demonstrate that TL is affected by intensive night work schedules, as work with six consecutive night for a period of more than 5 years was associated with decreased telomere lengths (−3.18, 95% CI: −6.46 to −0.58, P = 0.016). Furthermore, telomere shortening is associated with increased breast cancer risk in workers with long periods of consecutive night shifts. Thus, nurses with longer telomere lengths had a lower risk for breast cancer if they had worked more than four (OR: 0.37, 95% CI: 0.16–0.79, P = 0.014) or five (OR: 0.31, 95% CI: 0.10–0.83, P = 0.029) consecutive night shifts for a period of 5 years or more. These data suggest that telomere shortening is associated with the duration and intensity of night work and may be a contributing factor for breast cancer risk among female shift workers.

Abstract 2487: Functional characterization of the BRCA2 variant, K3326X

Abstract Individuals with germline mutations in the breast cancer susceptibility gene, BRCA2, have an approximate 70% risk of developing breast cancer, a 30% risk of developing ovarian cancer, a 20-fold increased risk of developing prostate cancer, and a 10-fold risk of developing pancreatic cancer during their lifetime. Loss of function germline mutations in BRCA2 affect its role in the homologous recombination (HR) DNA repair pathway leading to significant genomic instability. In addition to deleterious truncating mutations, several sequence variants, collectively called Variants of Unknown Significance (VUS), have been identified and are distributed along its length. One such variant is rs11571833, a nonsense mutation in the last exon (c.9976A&amp;gt;T, K3326X), resulting in the loss of the C-terminal 93 amino acid residues in BRCA2. This truncated variant has been previously described as a polymorphism that does not increase susceptibility to breast and ovarian cancers, and as a neutral unclassified variant non-deleterious to its function. However, recent studies identified K3326X to be enriched in breast cancer cases and to increase the risk for lung, pancreatic, ovarian, and upper aero-digestive tract cancers. Preliminary data, obtained from the Rutgers Cancer Institute of New Jersey breast cancer case-control study, identified K3326X enrichment in 1.25% of cases compared to 0.7% of controls. Several of the carriers had second primaries and displayed a trend toward increased number of family members diagnosed with colon cancer. Notably, K3326X was also identified in 1.38% (11 of 796) of our histologically-diverse cohort of genomically-profiled tumors that included cancers of the breast, ovarian/fallopian tube, lung, vulvar, cancer of unknown primary, and one breast cancer case having prolonged response to platinum-based therapy. Thus, K3326X may represent a functional loss of wild type BRCA2 function, as we observe concomitant loss of heterozygosity at this locus. In a preliminary study, we evaluated the K3326X variant, in vitro, in a functional DR-GFP-based reporter assay measuring HR. Our data reveal the BRCA2 K3326X variant to be impaired in the HR pathway indicating a loss of wild-type protein function. We will also evaluate cell viability of the K3326X variant in the presence of DNA damaging drugs like cisplatin, poly-ADP ribose polymerase inhibitors and mitomycin C. Future studies will also incorporate a retrospective evaluation of tumor specimens that have undergone comprehensive genomic profiling. These data would indicate that BRCA2 K3326X represents a functional hypomorphic variant that may have implications in therapeutic approaches and cancer risk evaluations across a spectrum of tumor types. Citation Format: Srilatha R. Simhadri, Sonia C. Dolfi, Atul Kulkarni, Bing Xia, Shridar Ganesan, Kim M. Hirshfield. Functional characterization of the BRCA2 variant, K3326X [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2487. doi:10.1158/1538-7445.AM2017-2487

Abstract LB-157: Association of aflatoxin and gallbladder cancer in Shanghai

Abstract Background: Aflatoxin, which is a risk factor for developing hepatocellular carcinoma, may also cause gallbladder cancer (GBC). We hypothesized that GBC patients have higher aflatoxin exposure than gallstone patients. Methods: We used samples and data from the Shanghai Biliary Tract Cancer Case-control Study conducted from 1997-2001. Of the 267 GBC and 730 gallstone participants with plasma available, 250 GBC patients and 250 controls with gallstones were randomly selected for measurement of aflatoxin B1 (AFB1)-lysine plasma adducts using isotope dilution mass spectrometry. In 54 GBC patients, tumor tissue was examined for the aflatoxin-related R249S TP53 mutation through targeted sequencing. Results: We calculated age- and sex-adjusted odds ratios (ORs) and 95% confidence intervals (CIs), as well as the population attributable fraction (PAF). AFB1-lysine adduct detection was nearly 3-fold higher in GBC patients (OR, 2.96; 95% CI, 1.90 to 4.61). Among the 85 GBC patients (34%) with detectable AFB1-lysine adduct levels, the median was 4.6 pg/mg, compared to 1.2 pg/mg among the 37 gallstone-patient controls (15%) with detectable levels, and the OR was 9.97(95% CI, 2.73 to 36.44) for quartile 4 versus 1 in GBC compared to gallstone patients. The PAF for cancer related to aflatoxin was 22% (95% CI: 17%-27%). In 54 GBC patients, tumor tissue was examined for the aflatoxin-related R249S TP53 mutation through targeted sequencing, however, all patients were negative for the mutation. Conclusions: Aflatoxin is significantly associated with GBC, although it does not appear to be correlated with the R249S TP53 mutation in the gallbladder. If aflatoxin is shown to cause GBC, it may have accounted for up to 22% of the gallbladder cancers in Shanghai during the study period and may account for an even higher proportion in high-risk areas. If verified, reducing aflatoxin exposure may reduce GBC incidence. Citation Format: Jill E. Koshiol, Yu-Tang Gao, Michael Dean, Patricia Egner, Chirag Nepal, Kristine Jones, Bingsheng Wang , Asif Rashid, Wen Lou, Alison Van Dyke, Catterina Ferreccio, Michael Malasky, Ming-Chang Shen, Bin zhu, Jesper Andersen, Allan Hildesheim, Ann W. Hsing, John Groopman. Association of aflatoxin and gallbladder cancer in Shanghai [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-157. doi:10.1158/1538-7445.AM2017-LB-157

Abstract 5283: Association between body mass index and prostate cancer among African American men

Abstract Prostate cancer (PCa) is a leading cause of cancer death in US men. Yet, the etiology of prostate cancer remains poorly understood, with only older age, African ancestry, family history of the disease, and multiple germline genetic variations being established disease risk factors. Prostate cancer occurs more often in African-American (AA) men and Caribbean men of African descent than in men of other race/ethnicities. While it has been previously suggested that obesity (measured using body mass index [BMI, kg/m2]) may worsen disease-related outcomes among prostate cancer patients, the relationship of obesity and prostate cancer risk, using race as a predictor, has not been fully explored. Using multivariable logistic regression, we estimated the risk of total PCa for 976 cases and 1,032 age-matched controls, with equal proportions of European-American (EA) and AA men. Among men in the NCI Maryland Prostate Cancer Case-Control Study, BMI was inversely associated with disease outcomes in AA men, but not among EA men. Consistent with previous literature, BMI in EA men was shown to be positively associated with overall prostate cancer risk. Our findings suggest an obesity paradox, where obesity may protect against incidence of PCa among AA men. Studies are needed to elucidate the underlying mechanisms responsible for the differential effects of obesity in AA and EA men with prostate cancer. Citation Format: Margaret S. Pichardo, Cheryl J. Smith, Wei Tang, Tiffany Dorsey, Stefan Ambs. Association between body mass index and prostate cancer among African American men [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5283. doi:10.1158/1538-7445.AM2017-5283

Aspirin Use Reduces the Risk of Aggressive Prostate Cancer and Disease Recurrence in African-American Men.

Background: Men of African descent experience a disproportionately high prostate cancer mortality. Intratumoral inflammation was found to be associated with aggressive prostate cancer. We and others have shown that prostate tumors in African-American (AA) patients harbor a distinct immune and inflammation signature when compared with European-American (EA) patients. These observations suggest that inflammation could be a driver of aggressive disease in men of African descent, leading to the hypothesis that an anti-inflammatory drug like aspirin could prevent disease progression.Methods: We examined the relationship between aspirin use and prostate cancer in the NCI-Maryland Prostate Cancer Case-Control Study consisting of 823 men with incident prostate cancer (422 AA and 401 EA) and 1,034 population-based men without the disease diagnosis (486 AA and 548 EA).Results: We observed a significant inverse association between regular aspirin use and prostate cancer among AA men. Stratification of AA patients by disease stage showed that daily and long-term (>3 years) aspirin use significantly decreased the risk of advanced disease [adjusted ORs for T3/T4 disease: 0.35, 95% confidence interval (CI), 0.17-0.73; and 0.22, 95% CI, 0.08-0.60, respectively], but not early-stage disease (T1/T2). Regular aspirin use also reduced disease recurrence in AA men.Conclusions: Regular aspirin use is associated with a decreased risk of advanced stage prostate cancer and increased disease-free survival in AA men.Impact: Regular aspirin use before and after a prostate cancer diagnosis may prevent the development of aggressive disease in AA men who are at risk of a lethal malignancy. Cancer Epidemiol Biomarkers Prev; 26(6); 845-53. ©2017 AACR.

BRCA2 Hypomorphic Missense Variants Confer Moderate Risks of Breast Cancer.

Breast cancer risks conferred by many germline missense variants in the BRCA1 and BRCA2 genes, often referred to as variants of uncertain significance (VUS), have not been established. In this study, associations between 19 BRCA1 and 33 BRCA2 missense substitution variants and breast cancer risk were investigated through a breast cancer case-control study using genotyping data from 38 studies of predominantly European ancestry (41,890 cases and 41,607 controls) and nine studies of Asian ancestry (6,269 cases and 6,624 controls). The BRCA2 c.9104A>C, p.Tyr3035Ser (OR = 2.52; P = 0.04), and BRCA1 c.5096G>A, p.Arg1699Gln (OR = 4.29; P = 0.009) variant were associated with moderately increased risks of breast cancer among Europeans, whereas BRCA2 c.7522G>A, p.Gly2508Ser (OR = 2.68; P = 0.004), and c.8187G>T, p.Lys2729Asn (OR = 1.4; P = 0.004) were associated with moderate and low risks of breast cancer among Asians. Functional characterization of the BRCA2 variants using four quantitative assays showed reduced BRCA2 activity for p.Tyr3035Ser compared with wild-type. Overall, our results show how BRCA2 missense variants that influence protein function can confer clinically relevant, moderately increased risks of breast cancer, with potential implications for risk management guidelines in women with these specific variants. Cancer Res; 77(11); 2789-99. ©2017 AACR.

Highlights of This Issue

Toth and colleagues used a subsets (ASSET) meta-analytic approach, to investigate associations of genetic variants related to epigenetic mechanisms with risks of breast, lung, colorectal, ovarian and prostate carcinomas. Among 162,887 imputed or genotyped variants in 555 candidate genes, SNPs in eight genes were associated with risk of more than one cancer type. Variants in BABAM1 were confirmed as a susceptibility locus for squamous cell lung, overall breast, ER-negative breast, overall prostate, overall and serous ovarian cancer. DPF1 rs12611084 was inversely associated with ER-negative breast, endometrioid ovarian, overall and aggressive prostate cancer risk. Functional and correlative studies are now needed to elucidate the potential links between germline genotype, epigenetic function, and cancer etiology.Lee and colleagues investigated the relationship between nut consumption and lung cancer in the Environment And Genetics in Lung cancer Etiology (EAGLE) study and the National Institutes of Health (NIH) American Association of Retired Persons (AARP) Diet and Health Study. The study found higher frequency of intake of nut consumption was inversely associated with overall lung cancer risk and associations were independent of cigarette smoking and other known risk factors.Li-Fraumeni syndrome (LFS) is associated with germline TP53 mutations and a very high lifetime cancer risk. Algorithms that assess a patient's risk of inherited cancer predisposition are ofta model en used in clinical counseling. Existing LFS criteria have limitations. Peng and colleagues present a Mendelian model, LFSPRO, which estimates TP53 mutation probability through the Elston-Stewart algorithm, and consequently estimates future risk of cancer. LFSPRO accurately predicted TP53 mutation carriers in a pediatric sarcoma cohort from MD Anderson Cancer Center. LFSPRO is more broadly applicable than the current clinical criteria and may improve clinical management for individuals and families with LFS.Men of African descent experience a disproportionately high prostate cancer mortality and studies have shown that prostate tumors in African-American (AA) patients harbor a distinct immune and inflammation signature when compared with European-American (EA) patients. Smith and colleagues examined the relationship between aspirin use and prostate cancer in the NCI-Maryland Prostate Cancer Case-Control Study consisting of men with incident prostate cancer and population-based men without the disease diagnosis. The authors report a significant inverse association between regular aspirin use and prostate cancer among AA men. Regular aspirin use before and after a prostate cancer diagnosis may prevent the development of aggressive disease in AA men who are at risk of a lethal malignancy.

Association of dietary fiber intake and gut microbiota in healthy adults.

1569 Background: Increasing evidence has shown that gut microbiota alterations may play a role in colorectal cancer risk. Diet, particularly fiber intake, may modify gut microbiota composition, which may consequently impact cancer risk development. We investigated the relationship between dietary fiber intake and gut microbiota in healthy humans. Methods: Using 16S rRNA gene sequencing, we assessed gut microbiota in fecal samples from 151 healthy adults in two independent study populations: Study A, n = 75 (healthy controls from a colorectal cancer case-control study), and Study B, n = 76 (polyp-free subjects from a cross-sectional colonoscopy study). We calculated energy-adjusted total dietary fiber intake of participants based on food frequency questionnaires. For each study population, we evaluated the relationship between quartiles of higher fiber intake as a continuous ordinal variable, and global gut microbiota community composition (via PERMANOVA of weighted UniFrac distance) and specific taxon abundance (via DESeq2). Results: We found that fiber intake was significantly associated with overall microbial community composition in Study B (p = 0.003) but not Study A (p = 0.68), after adjustment for age, sex, race, body mass index, and cigarette smoking. In a taxonomy-based meta-analysis of these two study populations, higher fiber intake was associated with lower abundance of genus Actinomyces (fold change [FC] = 0.769, p = 0.003), and higher abundance of genera Faecalibacterium (FC = 1.153, p = 0.03), Lachnospira (FC = 1.167, p = 0.04), and SMB53 (FC = 1.201, p = 0.05). A species-level meta-analysis showed an association between higher fiber intake and higher abundance of Faecalibacterium prausnitzii (FC = 1.165, p = 0.03) and lower abundance of Ruminococcus bromii (FC = 0.828, p = 0.08). Conclusions: Our results suggest that higher intake of dietary fiber may alter gut microbiota in healthy adults. Given the potentially modifiable nature of the gut microbiota through diet, these findings warrant further study of diet-microbiota based colorectal cancer prevention strategies.

Percent mammographic density prediction: development of a model in the nurses' health studies.

To develop a model to predict percent mammographic density (MD) using questionnaire data and mammograms from controls in the Nurses' Health Studies' nested breast cancer case-control studies. Further, we assessed the association between both measured and predicted percent MD and breast cancer risk. Using data from 2,955 controls, we assessed several variables as potential predictors. We randomly divided our dataset into a training dataset (two-thirds of the dataset) and a testing dataset (one-third of the dataset). We used stepwise linear regression to identify the subset of variables that were most predictive. Next, we examined the correlation between measured and predicted percent MD in the testing dataset and computed the r 2 in the total dataset. We used logistic regression to examine the association between measured and predicted percent MD and breast cancer risk. In the training dataset, several variables were selected for inclusion, including age, body mass index, and parity, among others. In the testing dataset, the Spearman correlation coefficient between predicted and measured percent MD was 0.61. As the prediction model performed well in the testing dataset, we developed the final model in the total dataset. The final prediction model explained 41% of the variability in percent MD. Both measured and predicted percent MD were similarly associated with breast cancer risk adjusting for age, menopausal status, and hormone use (OR per five unit increase=1.09 for both). These results suggest that predicted percent MD may be useful for research studies in which mammograms are unavailable.

Association of Aflatoxin and Gallbladder Cancer

Aflatoxin, which causes hepatocellular carcinoma, may also cause gallbladder cancer. We investigated whether patients with gallbladder cancer have higher exposure to aflatoxin than patients with gallstones. We measured aflatoxin B1 (AFB1)-lysine adducts in plasma samples from the Shanghai Biliary Tract Cancer case-control study, conducted from 1997 through 2001. We calculated age- and sex-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) and the population-attributable fraction for 209patients with gallbladder cancer and gallstones vs 250 patients with gallstones without cancer (controls). In 54 patients with gallbladder cancer, tumor tissue was examined for the R249S mutation in TP53, associated with aflatoxin exposure, through targeted sequencing. The AFB1-lysine adduct was detected in 67 (32%) of 209 patients with gallbladder cancer and 37 (15%) of the 250 controls (χ2P< .0001), almost threefold more patients with gallbladder cancer than controls (OR, 2.71; 95% CI, 1.70-4.33). Among participants with detectable levels of AFB1-lysine, the median level of AFB1-lysine was 5.4 pg/mg in those with gallbladder cancer, compared with 1.2 pg/mg in controls. For patients in the fourth quartile of AFB1-lysine level vs the first quartile, the OR for gallbladder cancer was 7.61 (95% CI, 2.01-28.84). None of the 54 gallbladder tumors sequenced were found to have the R249S mutation in TP53. The population-attributable fraction for cancer related to aflatoxin was 20% (95% CI, 15%-25%). In a case-control study of patients with gallbladder cancer and gallstones vs patients with gallstones without cancer, we associated exposure to aflatoxin (based on plasma level of AFB1-lysine) with gallbladder cancer. Gallbladder cancer does not appear associate with the R249S mutation in TP53. If aflatoxin is a cause of gallbladder cancer, it may have accounted for up to 20% of the gallbladder cancers in Shanghai, China, during the study period, and could account for an even higher proportion in high-risk areas. If our findings are verified, reducing aflatoxin exposure might reduce the incidence of gallbladder cancer.

Weighted pseudolikelihood for SNP set analysis with multiple secondary outcomes in case-control genetic association studies.

We propose a weighted pseudolikelihood method for analyzing the association of a SNP set, example, SNPs in a gene or a genetic pathway or network, with multiple secondary phenotypes in case-control genetic association studies. To boost analysis power, we assume that the SNP-specific effects are shared across all secondary phenotypes using a scaled mean model. We estimate regression parameters using Inverse Probability Weighted (IPW) estimating equations obtained from the weighted pseudolikelihood, which accounts for case-control sampling to prevent potential ascertainment bias. To test the effect of a SNP set, we propose a weighted variance component pseudo-score test. We also propose a penalized IPW pseudolikelihood method for selecting a subset of SNPs that are associated with the multiple secondary phenotypes. We show that the proposed variable selection procedure has the oracle properties and is robust to misspecification of the correlation structure among secondary phenotypes. We select the tuning parameter using a weighted Bayesian Information-like Criterion (wBIC). We evaluate the finite sample performance of the proposed methods via simulations, and illustrate the methods by the analysis of the multiple secondary smoking behavior outcomes in a lung cancer case-control genetic association study.

DNA Methylation-Derived Neutrophil-to-Lymphocyte Ratio: An Epigenetic Tool to Explore Cancer Inflammation and Outcomes.

Background: The peripheral blood neutrophil-to-lymphocyte ratio (NLR) is a cytologic marker of both inflammation and poor outcomes in patients with cancer. DNA methylation is a key element of the epigenetic program defining different leukocyte subtypes and may provide an alternative to cytology in assessing leukocyte profiles. Our aim was to create a bioinformatic tool to estimate NLR using DNA methylation, and to assess its diagnostic and prognostic performance in human populations.Methods: We developed a DNA methylation-derived NLR (mdNLR) index based on normal isolated leukocyte methylation libraries and established cell-mixture deconvolution algorithms. The method was applied to cancer case-control studies of the bladder, head and neck, ovary, and breast, as well as publicly available data on cancer-free subjects.Results: Across cancer studies, mdNLR scores were either elevated in cases relative to controls, or associated with increased hazard of death. High mdNLR values (>5) were strong indicators of poor survival. In addition, mdNLR scores were elevated in males, in nonHispanic white versus Hispanic ethnicity, and increased with age. We also observed a significant interaction between cigarette smoking history and mdNLR on cancer survival.Conclusions: These results mean that our current understanding of mature leukocyte methylomes is sufficient to allow researchers and clinicians to apply epigenetically based analyses of NLR in clinical and epidemiologic studies of cancer risk and survival.Impact: As cytologic measurements of NLR are not always possible (i.e., archival blood), mdNLR, which is computed from DNA methylation signatures alone, has the potential to expand the scope of epigenome-wide association studies. Cancer Epidemiol Biomarkers Prev; 26(3); 328-38. ©2016 AACR.

Stomach Cancer Following Hodgkin Lymphoma, Testicular Cancer and Cervical Cancer: A Pooled Analysis of Three International Studies with a Focus on Radiation Effects.

To further understand the risk of stomach cancer after fractionated high-dose radiotherapy, we pooled individual-level data from three recent stomach cancer case-control studies. These studies were nested in cohorts of five-year survivors of first primary Hodgkin lymphoma (HL), testicular cancer (TC) or cervical cancer (CX) from seven countries. Detailed data were abstracted from patient records and radiation doses were reconstructed to the site of the stomach cancer for cases and to the corresponding sites for matched controls. Among 327 cases and 678 controls, mean doses to the stomach were 15.3 Gy, 24.7 Gy and 1.9 Gy, respectively, for Hodgkin lymphoma, testicular cancer and cervical cancer survivors, with an overall mean dose of 10.3 Gy. Risk increased with increasing radiation dose to the stomach cancer site (P < 0.001) with no evidence of nonlinearity or of a downturn at the highest doses (≥35 Gy). The pooled excess odds ratio per Gy (EOR/Gy) was 0.091 [95% confidence interval (CI): 0.036-0.20] with estimates of 0.049 (95% CI: 0.007-0.16) for Hodgkin lymphoma, 0.27 (95% CI: 0.054-1.44) for testicular cancer and 0.096 (95% CI: -0.002-0.39) for cervical cancer (P homogeneity = 0.25). The EOR/Gy increased with time since exposure (P trend = 0.004), with an EOR/Gy of 0.38 (95% CI: 0.12-1.04) for stomach cancer occurring ≥20 years postirradiation corresponding to odds ratios of 4.8 and 10.5 at radiation doses to the stomach of 10 and 25 Gy, respectively. Of 111 stomach cancers occurring ≥20 years after radiotherapy, 63.8 (57%) could be attributed to radiotherapy. Our findings differ from those based on Japanese atomic-bomb survivors, where the overall EOR/Gy was higher and where there was no evidence of an increase with time since exposure. By pooling data from three studies, we demonstrated a clear increase in stomach cancer risk over a wide range of doses from fractionated radiotherapy with the highest risks occurring many years after exposure. These findings highlight the need to directly evaluate the health effects of high-dose fractionated radiotherapy rather than relying on the data of persons exposed at low and moderate acute doses.

Hypertension among adults exposed to drinking water arsenic in Northern Chile

BackgroundA growing number of studies have identified an association between exposure to inorganic arsenic and hypertension. However, results have not been consistent across studies. Additional studies are warranted, given the global prevalence of both arsenic exposure and morbidity attributable to hypertension. MethodsWe analyzed data collected from October 2007-December 2010 for a population-based cancer case-control study in northern Chile. Data included lifetime individual arsenic exposure estimates and information on potential confounders for a total of 1266 subjects. Those self-reporting either a physician diagnosis of hypertension or use of an anti-hypertensive medication were classified as having hypertension (n=612). The association between hypertension and drinking water arsenic exposure was analyzed using logistic regression models. ResultsCompared to those in the lowest category for lifetime highest 5-year average arsenic exposure (<60µg/L), those in the middle (60–623μg/L) and upper (>623μg/L) exposure categories had adjusted hypertension ORs of 1.49 (95% CI: 1.09, 2.05) and 1.65 (95% CI: 1.18, 2.32), respectively. Similar results were observed in analyses of lifetime cumulative exposures and analyses restricted to exposures from the distant past. ConclusionsWe identified evidence of increased odds of hypertension with exposure to arsenic in drinking water among study participants. Our findings add to the growing body of research supporting this association, which could have important public health implications.

Association between Dietary Isoflavones in Soy and Legumes and Endometrial Cancer: A Systematic Review and Meta-Analysis

BackgroundEpidemiologic studies have reported conflicting findings between soy- and legume-derived dietary isoflavones and risk of endometrial cancer. ObjectiveThe aim of the present meta-analysis was to quantitatively investigate the association between daily intake of soy- and legume-derived isoflavones and risk of endometrial cancer. DesignA broad search was conducted in the following electronic databases: PubMed, EMBASE, Google Scholar, the Cochrane Library, the China Knowledge Resource Integrated Database, and the Chinese Biomedical Database based on combinations of the key words endometrial cancer, isoflavone, soy, and legume for epidemiologic studies that focused on relationships between dietary isoflavones and endometrial cancer risk. A fixed-effect or random-effect model was used to pool study-specific risk estimates. ResultsA total of 13 epidemiologic studies were included in the present meta-analysis, consisting of three prospective cohort studies and 10 population-based case-control studies. The final results indicated that higher dietary isoflavone levels from soy products and legumes were associated with a reduced risk of endometrial cancer (odds ratio [OR] 0.81, 95% CI 0.74 to 0.89). Low heterogeneous bias was observed (I2=11.7%; P=0.327). Subgroup analyses were conducted based on study design, source of dietary isoflavones, and study region. When restricted to study design, dietary isoflavones from soy and legumes played a role in prevention of endometrial cancer in case-control studies (OR 0.81, 95% CI 0.73 to 0.90). However, there did not appear to be an association between dietary isoflavones and endometrial cancer in cohort studies (OR 0.81, 95% CI 0.66 to 1.00). Significant associations were found between dietary isoflavones from soy products (OR 0.82, 95% CI 0.72 to 0.92) and legumes (OR 0.84, 95% CI 0.74 to 0.96) and endometrial cancer. Dietary isoflavones were associated with reduced incidence of endometrial cancer, both in Asian countries (OR 0.78, 95% CI 0.66 to 0.93) and non-Asian countries (OR 0.82, 95% CI 0.73 to 0.92). ConclusionsThe findings suggest a weak inverse association between higher consumption of dietary isoflavones from soy products and legumes and endometrial cancer risk. However, there is still a need for large, prospective epidemiologic studies that provide a higher level of evidence to verify these findings.