Subgroup-specific associations in the face of overall null results: should we rush in or fear to tread?

Association of prenatal exposure to ambient air pollution with adverse birth outcomes and effect modification by socioeconomic factors

BACKGROUND

Maternal exposure to air pollution has been associated with birth outcomes; however, few studies examined biologically critical exposure windows shorter than trimesters or potential effect modifiers.

OBJECTIVES

To examine associations of prenatal fine particulate matter (PM_2.5), by trimester and in biologically critical windows, with birth outcomes and assess potential effect modifiers.

METHODS

This study used two pregnancy cohorts (CANDLE and TIDES; N = 2099) in the ECHO PATHWAYS Consortium. PM_2.5 was estimated at the maternal residence using a fine-scale spatiotemporal model, averaged over pregnancy, trimesters, and critical windows (0-2 weeks, 10-12 weeks, and last month of pregnancy). Outcomes were preterm birth (PTB, <37 completed weeks of gestation), small-for-gestational-age (SGA), and continuous birthweight. We fit multivariable adjusted linear regression models for birthweight and Poisson regression models (relative risk, RR) for PTB and SGA. Effect modification by socioeconomic factors (maternal education, household income, neighborhood deprivation) and infant sex were examined using interaction terms.

RESULTS

Overall, 9% of births were PTB, 10.4% were SGA, and mean term birthweight was 3268 g (SD = 558.6). There was no association of PM_2.5 concentration with PTB or SGA. Lower birthweight was associated with higher PM_2.5 averaged over pregnancy (β -114.2, 95%CI -183.2, -45.3), during second (β -52.9, 95%CI -94.7, -11.2) and third (β -45.5, 95%CI -85.9, -5.0) trimesters, and the month prior to delivery (β -30.5, 95%CI -57.6, -3.3). Associations of PM_2.5 with likelihood of SGA and lower birthweight were stronger among male infants (p-interaction ≤0.05) and in those with lower household income (p-interaction = 0.09).

CONCLUSIONS

Findings from this multi city U.S. birth cohort study support previous reports of inverse associations of birthweight with higher PM_2.5 exposure during pregnancy. Findings also suggest possible modification of this association by infant sex and household income.

Sex differences in associations between birth characteristics and childhood cancers: a five-state registry-linkage study

BACKGROUND

There is a well-recognized male excess in childhood cancer incidence; however, it is unclear whether there is etiologic heterogeneity by sex when defined by epidemiologic risk factors.

METHODS

Using a 5-state registry-linkage study (cases n = 16,411; controls n = 69,816), we estimated sex-stratified odds ratios (OR) and 95% confidence intervals (95% CI) between birth and demographic characteristics for 16 pediatric cancers. Evidence of statistical interaction (p-interaction < 0.01) by sex was evaluated for each characteristic in each cancer.

RESULTS

Males comprised > 50% of cases for all cancers, except Wilms tumor (49.6%). Sex interacted with a number of risk factors (all p-interaction < 0.01) including gestational age for ALL (female, 40 vs. 37-39 weeks OR: 0.84, 95% CI 0.73-0.97) and ependymoma (female, 40 vs. 37-39 OR: 1.78, 95% CI 1.14-2.79; female, ≥ 41 OR: 2.01. 95% CI 1.29-3.14), birth order for AML (female,  ≥ 3rd vs. 1st OR: 1.39, 95% CI 1.01-1.92), maternal education for Hodgkin lymphoma (male, any college vs. < high school[HS] OR: 1.47, 95% CI 1.03-2.09) and Wilms tumor (female, any college vs. HS OR: 0.74, 95% CI 0.59-0.93), maternal race/ethnicity for neuroblastoma (male, black vs. white OR: 2.21, 95% CI 1.21-4.03; male, Hispanic vs. white OR: 1.86, 95% CI 1.26-2.75; female, Asian/Pacific Islander vs. white OR: 0.28, 95% CI 0.12-0.69), and paternal age (years) for hepatoblastoma in males (< 24 vs. 25-29 OR: 2.17, 95% CI 1.13-4.19; ≥ 35 vs. 25-29 OR: 2.44, 95% CI 1.28-4.64).

CONCLUSIONS

These findings suggest etiologic heterogeneity by sex for childhood cancers for gestational age, maternal education, and race/ethnicity and paternal age.

Fine Particulate Matter and Dementia Incidence in the Adult Changes in Thought Study

BACKGROUND

Air pollution may be associated with elevated dementia risk. Prior research has limitations that may affect reliability, and no studies have evaluated this question in a population-based cohort of men and women in the United States.

OBJECTIVES

We evaluated the association between time-varying, 10-y average fine particulate matter (PM2.5) exposure and hazard of all-cause dementia. An additional goal was to understand how to adequately control for age and calendar-time-related confounding through choice of the time axis and covariate adjustment.

METHODS

Using the Adult Changes in Thought (ACT) population-based prospective cohort study in Seattle, we linked spatiotemporal model-based PM2.5 exposures to participant addresses from 1978 to 2018. Dementia diagnoses were made using high-quality, standardized, consensus-based protocols at biennial follow-ups. We conducted multivariable Cox proportional hazards regression to evaluate the association between time-varying, 10-y average PM2.5 exposure and time to event in a model with age as the time axis, stratified by apolipoprotein E (APOE) genotype, and adjusted for sex, education, race, neighborhood median household income, and calendar time. Alternative models used calendar time as the time axis.

RESULTS

We report 1,136 cases of incident dementia among 4,166 individuals with nonmissing APOE status. Mean [mean ± standard deviation (SD)] 10-y average PM2.5 was 10.1 (±2.9) μg/m3. Each 1-μg/m3 increase in the moving average of 10-y PM2.5 was associated with a 16% greater hazard of all-cause dementia [1.16 (95% confidence interval: 1.03, 1.31)]. Results using calendar time as the time axis were similar.

DISCUSSION

In this prospective cohort study with extensive exposure data and consensus-based outcome ascertainment, elevated long-term exposure to PM2.5 was associated with increased hazard of all-cause dementia. We found that optimal control of age and time confounding could be achieved through use of either age or calendar time as the time axis in our study. Our results strengthen evidence on the neurodegenerative effects of PM2.5. https://doi.org/10.1289/EHP9018.

Case-control investigation of occupational lead exposure and kidney cancer

Objectives

Lead is a suspected carcinogen that has been inconsistently associated with kidney cancer. To clarify this relationship, we conducted an analysis of occupational lead exposure within a population-based study of kidney cancer using detailed exposure assessment methods.

Methods

Study participants (1217 cases and 1235 controls), enrolled between 2002 and 2007, provided information on their occupational histories and, for selected lead-related occupations, answered questions regarding workplace tasks, and use of protective equipment. Industrial hygienists used this information to develop several estimates of occupational lead exposure, including probability, duration and cumulative exposure. Unconditional logistic regression was used to compute ORs and 95% CIs for different exposure metrics, with unexposed subjects serving as the reference group. Analyses were also conducted stratifying on several factors, including for subjects of European ancestry only, single nucleotide polymorphisms in ALAD (rs1805313, rs1800435, rs8177796, rs2761016), a gene involved in lead toxicokinetics.

Results

In our study, cumulative occupational lead exposure was not associated with kidney cancer (OR 0.9, 95% CI 0.7 to 1.3 for highest quartile vs unexposed; ptrend=0.80). Other lead exposure metrics were similarly null. We observed no evidence of effect modification for the evaluated ALAD variants (subjects of European ancestry only, 662 cases and 561 controls) and most stratifying factors, although lead exposure was associated with increased risk among never smokers.

Conclusions

The findings of this study do not offer clear support for an association between occupational lead exposure and kidney cancer.

Ambient Air Pollution Exposure and Fecundability in Women Undergoing In Vitro Fertilization

BACKGROUND

Limited research suggests ambient air pollution impairs fecundity but groups most susceptible have not been identified. We studied whether long-term ambient air pollution exposure prior to an in vitro fertilization (IVF) cycle was associated with successful livebirth, and whether associations were modified by underlying infertility diagnosis.

METHODS

Data on women initiating their 1st autologous IVF cycle in 2012-13 were obtained from four U.S. clinics. Outcomes included pregnancy, pregnancy loss, and livebirth. Annual average exposure to fine particulate matter (PM2.5), PM10, and nitrogen dioxide (NO2) prior to IVF start were estimated at residential address using a validated national spatial model incorporating land-use regression and universal kriging. We also assessed residential distance to major roadway. We calculated risk ratios (RR) using modified Poisson regression and evaluated effect modification (EM) by infertility diagnosis on additive and multiplicative scales.

RESULTS

Among 7,463 eligible participants, 36% had a livebirth. There was a non-significant indication of an association between PM2.5 or NO2 and decreased livebirth and increased pregnancy loss. Near roadway residence was associated with decreased livebirth (RR: 0.96, 95% CI: 0.82, 0.99. There was evidence for EM between high exposure to air pollutants and a diagnosis of diminished ovarian reserve (DOR) or male infertility and decreased livebirth.

CONCLUSIONS

Despite suggestive but uncertain findings for the overall effect of air pollution on fecundity, we found a suggestive indication that there may be synergistic effects of air pollution and DOR or male infertility diagnosis on livebirth. This suggests two possible targets for future research and intervention.

Constrained Score Statistics Identify Genetic Variants Interacting with Multiple Risk Factors in Barrett's Esophagus

Few gene-environment interactions (G × E) have been discovered in cancer epidemiology thus far, in part due to the large number of possible G × E to be investigated and inherent low statistical power of traditional analytic methods for discovering G × E. We consider simultaneously testing for interactions between several related exposures and a genetic variant in a genome-wide study. To improve power, constrained testing strategies are proposed for multivariate gene-environment interactions at two levels: interactions that have the same direction (one-sided or bidirectional hypotheses) or are proportional to respective exposure main effects (a variant of Tukey's one-degree test). Score statistics were developed to expedite the genome-wide computation. We conducted extensive simulations to evaluate validity and power performance of the proposed statistics, applied them to the genetic and environmental exposure data for esophageal adenocarcinoma and Barrett's esophagus from the Barretts Esophagus and Esophageal Adenocarcinoma Consortium (BEACON), and discovered three loci simultaneously interacting with gastresophageal reflux, obesity, and tobacco smoking with genome-wide significance. These findings deepen understanding of the genetic and environmental architecture of Barrett's esophagus and esophageal adenocarcinoma.

A perspective on interaction effects in genetic association studies

The identification of gene–gene and gene–environment interaction in human traits and diseases is an active area of research that generates high expectation, and most often lead to high disappointment. This is partly explained by a misunderstanding of the inherent characteristics of standard regression‐based interaction analyses. Here, I revisit and untangle major theoretical aspects of interaction tests in the special case of linear regression; in particular, I discuss variables coding scheme, interpretation of effect estimate, statistical power, and estimation of variance explained in regard of various hypothetical interaction patterns. Linking this components it appears first that the simplest biological interaction models—in which the magnitude of a genetic effect depends on a common exposure—are among the most difficult to identify. Second, I highlight the demerit of the current strategy to evaluate the contribution of interaction effects to the variance of quantitative outcomes and argue for the use of new approaches to overcome this issue. Finally, I explore the advantages and limitations of multivariate interaction models, when testing for interaction between multiple SNPs and/or multiple exposures, over univariate approaches. Together, these new insights can be leveraged for future method development and to improve our understanding of the genetic architecture of multifactorial traits.

Brain tumours and cigarette smoking: analysis of the INTERPHONE Canada case-control study

BACKGROUND

There is conflicting evidence regarding the associations between cigarette smoking and glioma or meningioma. Our purpose is to provide further evidence on these possible associations.

METHODS

We conducted a set of case-control studies in three Canadian cities, Montreal, Ottawa and Vancouver. The study included 166 subjects with glioma, 93 subjects with meningioma, and 648 population-based controls. A lifetime history of cigarette smoking was collected and various smoking indices were computed. Multivariable logistic regression was used to estimate odds ratios (ORs) between smoking and each of the two types of brain tumours.

RESULTS

Adjusted ORs between smoking and each type of brain tumour were not significantly elevated for all smokers combined or for smokers with over 15 pack-years ((packs / day) x years) accumulated. We tested for interactions between smoking and several sociodemographic variables; the interaction between smoking and education on glioma risk was significant, with smoking showing an elevated OR among subjects with lower education and an OR below unity among subjects with higher education.

CONCLUSION

Except for an unexplained and possibly artefactual excess risk in one population subgroup, we found little or no evidence of an association between smoking and either glioma or meningioma.

Cardiovascular and mortality risk in elderly Medicare beneficiaries treated with olmesartan versus other angiotensin receptor blockers

PURPOSE

In the randomized trial, Randomized Olmesartan and Diabetes Microalbuminuria Prevention, acute cardiovascular death was increased nearly fivefold in diabetic patients treated with high-dose olmesartan, an angiotensin receptor blocker (ARB), compared with placebo.

METHODS

Medicare beneficiaries were entered into new-user cohorts of olmesartan or other ARBs and followed on therapy for occurrence of acute myocardial infarction, stroke, or death. Analyses focused on specific subgroups defined by diabetes status, ARB dose, and duration of therapy. Hazard ratios (HR) with 95% confidence intervals (CIs) were estimated using Cox proportional hazards regression, with other ARBs as reference.

RESULTS

A total of 158,054 olmesartan and 724,673 other ARB users were followed for 54,285 and 260,390 person-years, respectively, during which 9237 endpoint events occurred. Lower-dose olmesartan was not associated with increased risk for any endpoint, regardless of duration of use. High-dose olmesartan for 6 months or longer was associated with increased risk of death in patients with diabetes (HR 2.03, 95%CI 1.09-3.75, p = 0.02) and with reduced risk in nondiabetic patients (HR 0.46, 95%CI 0.24-0.86, p = 0.01). Some, but not all, sensitivity analyses suggested that selective prescribing of olmesartan to healthier patients (channeling bias) may have accounted for the reduced risk in nondiabetic patients.

CONCLUSIONS

High-dose olmesartan was associated with an increased risk of death in diabetic patients treated for 6 months or longer and with a reduced risk of death in nondiabetic patients, when compared with use of other ARBs. This latter effect was probably because of selective prescribing of olmesartan to healthier patients, although effect modification cannot be excluded. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Evidence of subgroup-specific treatment effect in the absence of an overall effect: is there really a contradiction?

PURPOSE

Interaction and subgroup analyses remain controversial topics in epidemiology. A recent theoretical paper suggested that a combination of no overall treatment-outcome association and treatment effect limited to a single subgroup would imply a clinically implausible interaction, with opposite treatment effects in the two subgroups. However, this argument was based entirely on point estimates and ignored sampling error and statistical inference.

METHODS

We simulated hypothetical studies in which treatment truly affected the outcome in only one subgroup, with no effect in the other subgroup. We generated 1000 random samples for three study designs (small clinical study, case-control, and large cohort), and different values of total sample size (N), relative size of the affected subgroup, and treatment effect. We estimated the frequency of significant results for tests of overall and subgroup-specific treatment effects, and treatment-by-subgroup interaction.

RESULTS

Combination of statistically non-significant overall treatment effect and significant treatment-by-subgroup interaction occurred frequently, especially if the affected subgroup was proportionally smaller, even in studies with high power to detect the overall effect (e.g. in 37.1% of samples with N = 20 000, with 600 outcomes, and an effect (odds ratio of 1.5) limited to 30% of subjects). Furthermore, in most samples with a significant interaction, subgroup analyses correctly indicated that the significant effect was limited to one subgroup.

CONCLUSION

In studies where the treatment truly affects the risks in only one subgroup, a non-significant overall effect will often coincide with a statistically significant treatment-by-subgroup interaction. Thus, a non-significant overall effect should not prevent testing plausible interactions.

The Interaction between Pesticide Use and Genetic Variants Involved in Lipid Metabolism on Prostate Cancer Risk

Background. Lipid metabolism processes have been implicated in prostate carcinogenesis. Since several pesticides are lipophilic or are metabolized via lipid-related mechanisms, they may interact with variants of genes in the lipid metabolism pathway. Methods. In a nested case-control study of 776 cases and 1444 controls from the Agricultural Health Study (AHS), a prospective cohort study of pesticide applicators, we examined the interactions between 39 pesticides (none, low, and high exposure) and 220 single nucleotide polymorphisms (SNPs) in 59 genes. The false discovery rate (FDR) was used to account for multiple comparisons. Results. We found 17 interactions that displayed a significant monotonic increase in prostate cancer risk with pesticide exposure in one genotype and no significant association in the other genotype. The most noteworthy association was for ALOXE3 rs3027208 and terbufos, such that men carrying the T allele who were low users had an OR of 1.86 (95% CI = 1.16–2.99) and high users an OR of 2.00 (95% CI = 1.28–3.15) compared to those with no use of terbufos, while men carrying the CC genotype did not exhibit a significant association. Conclusion. Genetic variation in lipid metabolism genes may modify pesticide associations with prostate cancer; however our results require replication.

Genetic variation in base excision repair pathway genes, pesticide exposure, and prostate cancer risk

BACKGROUND

Previous research indicates increased prostate cancer risk for pesticide applicators and pesticide manufacturing workers. Although underlying mechanisms are unknown, evidence suggests a role of oxidative DNA damage.

OBJECTIVES

Because base excision repair (BER) is the predominant pathway involved in repairing oxidative damage, we evaluated interactions between 39 pesticides and 394 tag single-nucleotide polymorphisms (SNPs) for 31 BER genes among 776 prostate cancer cases and 1,444 male controls in a nested case-control study of white Agricultural Health Study (AHS) pesticide applicators.

METHODS

We used likelihood ratio tests from logistic regression models to determine p-values for interactions between three-level pesticide exposure variables (none/low/high) and SNPs (assuming a dominant model), and the false discovery rate (FDR) multiple comparison adjustment approach.

RESULTS

The interaction between fonofos and rs1983132 in NEIL3 [nei endonuclease VIII-like 3 (Escherichia coli)], which encodes a glycosylase that can initiate BER, was the most significant overall [interaction p-value (pinteract) = 9.3 × 10-6; FDR-adjusted p-value = 0.01]. Fonofos exposure was associated with a monotonic increase in prostate cancer risk among men with CT/TT genotypes for rs1983132 [odds ratios (95% confidence intervals) for low and high use compared with no use were 1.65 (0.91, 3.01) and 3.25 (1.78, 5.92), respectively], whereas fonofos was not associated with prostate cancer risk among men with the CC genotype. Carbofuran and S-ethyl dipropylthiocarbamate (EPTC) interacted similarly with rs1983132; however, these interactions did not meet an FDR < 0.2.

CONCLUSIONS

Our significant finding regarding fonofos is consistent with previous AHS findings of increased prostate cancer risk with fonofos exposure among those with a family history of prostate cancer. Although requiring replication, our findings suggest a role of BER genetic variation in pesticide-associated prostate cancer risk.

Haplotypes of DNA repair and cell cycle control genes, X-ray exposure, and risk of childhood acute lymphoblastic leukemia

BACKGROUND

Acute leukemias of childhood are a heterogeneous group of malignancies characterized by cytogenetic abnormalities, such as translocations and changes in ploidy. These abnormalities may be influenced by altered DNA repair and cell cycle control processes.

METHODS

We examined the association between childhood acute lymphoblastic leukemia (ALL) and 32 genes in DNA repair and cell cycle pathways using a haplotype-based approach, among 377 childhood ALL cases and 448 controls enrolled during 1995-2002.

RESULTS

We found that haplotypes in APEX1, BRCA2, ERCC2, and RAD51 were significantly associated with total ALL, while haplotypes in NBN and XRCC4, and CDKN2A were associated with structural and numerical change subtypes, respectively. In addition, we observed statistically significant interaction between exposure to 3 or more diagnostic X-rays and haplotypes of XRCC4 on risk of structural abnormality-positive childhood ALL.

CONCLUSIONS

These results support a role of altered DNA repair and cell cycle processes in the risk of childhood ALL, and show that this genetic susceptibility can differ by cytogenetic subtype and may be modified by exposure to ionizing radiation. To our knowledge, our study is the first to broadly examine the DNA repair and cell cycle pathways using a haplotype approach in conjunction with X-ray exposures in childhood ALL risk. If confirmed, future studies are needed to identify specific functional SNPs in the regions of interest identified in this analysis.

Pediatric germ cell tumors and parental infertility and infertility treatment: a Children's Oncology Group report

BACKGROUND

Few risk factors have been established for childhood germ cell tumors (GCT). Parental infertility and infertility treatment may be associated with GCT development but these risk factors have not been fully investigated.

METHODS

A case-control study of childhood GCT was conducted through the Children's Oncology Group (COG). Cases, under the age of 15 years at diagnosis, were recruited through COG institutions from January 1993 to December 2002. Controls were obtained through random digit dialing. Information about infertility and infertility treatment along with demographic factors was collection through maternal interviews. Subgroups created by gender, age at diagnosis, and tumor location were examined separately. Statistical analysis was performed using multivariate logistic regression models.

RESULTS

Overall, no association between GCT and infertility or its treatment was found. In subgroup analysis, females whose mothers had two or more fetal losses were found to be at increased risk for non-gonadal tumors (Odds ratio (OR)=3.32, 95% Confidence interval (CI)=1.12-9.88). Younger maternal age was associated with a lower risk of gonadal GCT in females (OR=0.52, 95% CI=0.28-0.96). There was an increased risk of all GCT and gonadal GCT in males born to older mothers (OR=2.88, 95% CI=1.13-7.37 and OR=3.70, 95% CI=1.12-12.24).

CONCLUSION

While no association between parental infertility or its treatment and childhood GCT was found overall, possible associations with maternal age and history of recurrent fetal loss were found in subgroups defined by gender.

Genome-wide meta-analysis of joint tests for genetic and gene-environment interaction effects

BACKGROUND

There is growing interest in the study of gene-environment interactions in the context of genome-wide association studies (GWASs). These studies will likely require meta-analytic approaches to have sufficient power.

METHODS

We describe an approach for meta-analysis of a joint test for genetic main effects and gene-environment interaction effects. Using simulation studies based on a meta-analysis of five studies (total n = 10,161), we compare the power of this test to the meta-analysis of marginal test of genetic association and the meta-analysis of standard 1 d.f. interaction tests across a broad range of genetic main effects and gene-environment interaction effects.

RESULTS

We show that the joint meta-analysis is valid and can be more powerful than classical meta-analytic approaches, with a potential gain of power over 50% compared to the marginal test. The standard interaction test had less than 1% power in almost all the situations we considered. We also show that regardless of the test used, sample sizes far exceeding those of a typical individual GWAS will be needed to reliably detect genes with subtle gene-environment interaction patterns.

CONCLUSION

The joint meta-analysis is an attractive approach to discover markers which may have been missed by initial GWASs focusing on marginal marker-trait associations.

Endometrial cancer and genetic variation in PTEN, PIK3CA, AKT1, MLH1, and MSH2 within a population-based case-control study

OBJECTIVE

We assessed whether common genetic variation in PTEN, PIK3CA, AKT1, MLH1, and MSH2-genes that reportedly are frequently altered in endometrial cancer-was associated with risk of endometrial cancer.

METHODS

Using data from a population-based case-control study in Poland (PECS) of 417 cases and 407 matched controls, we genotyped 76 tagging single nucleotide polymorphisms (tagSNPs; located in or within 10 kb upstream or 5 kb downstream of the gene of interest, minor allele frequency >=5% among various ethnic groups, and not already represented by another tagSNP at a LD of r(2) >=0.80) on an Illumina Custom Infinium iSelect assay that included over 29,000 SNPs in 1316 genes. For individual SNPs, we used unconditional logistic regression models, adjusted for age and site, to generate odds ratios (ORs) and 95% confidence intervals (CIs). To replicate the one statistically significant association in PECS, we independently genotyped that tagSNP among 1141 endometrial cancer cases and 2275 controls from the SEARCH study in the UK. We assessed haplotypes via extended haplotype blocks and the sequential haplotype scan method.

RESULTS

The rs2677764 tagSNP in PIK3CA was statistically significantly associated with endometrial cancer in PECS (OR=1.42, 95% CI, 1.03-1.95; P=0.03) but not SEARCH (OR=0.98, 95% CI=0.82-1.17). Of the 25 haplotypes observed in at least 5% of cases and controls in PECS, only 1, in PIK3CA, was statistically significantly associated with endometrial cancer (OR=1.39, 95% CI, 1.00-1.93). All haplotype global p-values were null.

CONCLUSION

Common genetic variation in PTEN, PIK3CA, AKT1, MLH1, or MSH2 was not statistically significantly associated with endometrial cancer.

N-acetyltransferase 2, exposure to aromatic and heterocyclic amines, and receptor-defined breast cancer

The role of N-acetyltransferase 2 (NAT2) polymorphism in breast cancer is still unclear. We explored the associations between potential sources of exposure to aromatic and heterocyclic amines (AHA), acetylation status and receptor-defined breast cancer in 1020 incident cases and 1047 population controls of the German GENICA study. Acetylation status was assessed as slow or fast. Therefore, NAT2 haplotypes were estimated using genotype information from six NAT2 polymorphisms. Most probable haplotypes served as alleles for the deduction of NAT2 acetylation status. The risks of developing estrogen receptor alpha (ER) and progesterone receptor (PR)-positive or negative tumors were estimated for tobacco smoking, consumption of red meat, grilled food, coffee, and tea, as well as expert-rated occupational exposure to AHA with logistic regression conditional on age and adjusted for potential confounders. Joint effects of these factors and NAT2 acetylation status were investigated. Frequent consumption of grilled food and coffee showed higher risks in slow acetylators for receptor-negative tumors [grilled food: ER-: odds ratio (OR) 2.57, 95% confidence interval (CI) 1.07-6.14 for regular vs. rare; coffee: ER-: OR 2.55, 95% CI 1.22-5.33 for >or=4 vs. 0 cups/day]. We observed slightly higher risks for never smokers that are fast acetylators for receptor-positive tumors compared with slow acetylators (ER-: OR 1.32, 95% CI 1.00-1.73). Our results support differing risk patterns for receptor-defined breast cancer. However, the modifying role of NAT2 for receptor-defined breast cancer is difficult to interpret in the light of complex mixtures of exposure to AHA.

Genetic susceptibility to distinct bladder cancer subphenotypes

BACKGROUND

Clinical, pathologic, and molecular evidence indicate that bladder cancer is heterogeneous with pathologic/molecular features that define distinct subphenotypes with different prognoses. It is conceivable that specific patterns of genetic susceptibility are associated with particular subphenotypes.

OBJECTIVE

To examine evidence for the contribution of germline genetic variation to bladder cancer heterogeneity.

DESIGN, SETTING, AND PARTICIPANTS

The Spanish Bladder Cancer/EPICURO Study is a case-control study based in 18 hospitals located in five areas in Spain. Cases were patients with a newly diagnosed, histologically confirmed, urothelial cell carcinoma of the bladder from 1998 to 2001. Case diagnoses were reviewed and uniformly classified by pathologists following the World Health Organisation/International Society of Urological Pathology 1999 criteria. Controls were hospital-matched patients (n=1149).

MEASUREMENTS

A total of 1526 candidate variants in 423 candidate genes were analysed. Three distinct subphenotypes were defined according to stage and grade: low-grade nonmuscle invasive (n=586), high-grade nonmuscle invasive (n=219), and muscle invasive (n=246). The association between each variant and subphenotype was assessed by polytomous risk models adjusting for potential confounders. Heterogeneity in genetic susceptibility among subphenotypes was also tested.

RESULTS AND LIMITATIONS

Two established bladder cancer susceptibility genotypes, NAT2 slow-acetylation and GSTM1-null, exhibited similar associations among the subphenotypes, as did VEGF-rs25648, which was previously identified in our study. Other variants conferred risks for specific tumour subphenotypes such as PMS2-rs6463524 and CD4-rs3213427 (respective heterogeneity p values of 0.006 and 0.004), which were associated with muscle-invasive tumours (per-allele odds ratios [95% confidence interval] of 0.56 [0.41-0.77] and 0.71 [0.57-0.88], respectively) but not with non-muscle-invasive tumours. Heterogeneity p values were not robust in multiple testing according to their false-discovery rate.

CONCLUSIONS

These exploratory analyses suggest that genetic susceptibility loci might be related to the molecular/pathologic diversity of bladder cancer. Validation through large-scale replication studies and the study of additional genes and single nucleotide polymorphisms are required.

Reproductive factors, exogenous hormone use and risk of lymphoid neoplasms among women in the National Institutes of Health-AARP Diet and Health Study Cohort

Reasons for higher incidence of lymphoid neoplasms among men than women are unknown. Because female sex hormones have immunomodulatory effects, reproductive factors and exogenous hormone use may affect risk for lymphoid malignancies. Previous epidemiologic studies on this topic have yielded conflicting results. Within the National Institutes of Health-AARP Diet and Health Study cohort, we prospectively analyzed detailed, questionnaire-derived information on menstrual and reproductive factors and use of oral contraceptives and menopausal hormone therapy among 134,074 US women. Using multivariable proportional hazards regression models, we estimated relative risks (RRs) for 85 plasma cell neoplasms and 417 non-Hodgkin lymphomas (NHLs) identified during follow-up from 1996 to 2002. We observed no statistically significant associations between plasma cell neoplasms, NHL, or the 3 most common NHL subtypes and age at menarche, parity, age at first birth, oral contraceptive use or menopausal status at baseline. For menopausal hormone therapy use, overall associations between NHL and unopposed estrogen and estrogen plus progestin were null, with the potential exception of an inverse association (RR = 0.49, 95% CI, 0.25-0.96) between use of unopposed estrogen and diffuse large B-cell lymphoma (DLBCL), the most common NHL subtype, among women with a hysterectomy. These data do not support an important role for reproductive factors or exogenous hormones in modulating lymphomagenesis.

Genetic variation in telomere maintenance genes, telomere length, and lung cancer susceptibility

Telomeres are responsible for the protection of the chromosome ends and shortened telomere length has been associated with risk of multiple cancers. Genetic variation in telomere-related genes may alter cancer risk associated with telomere length. Using lung cancer cases (n=120) and population-based controls (n=110) from Xuanwei, China, we analyzed telomere length separately and in conjunction with single nucleotide polymorphisms in the telomere maintenance genes POT1, TERT, and TERF2, which we have previously reported were associated with risk of lung cancer in this study. POT1 rs10244817, TERT rs2075786, and TERF2 rs251796 were significantly associated with lung cancer (p(trend)< or =0.05). The shortest tertile of telomere length was not significantly associated with risk of lung cancer (OR=1.58; 95% CI=0.79-3.18) when compared to the longest tertile of telomere length. When stratified by genotype, there was a suggestion of a dose-response relationship between tertiles of telomere length and risk of lung cancer among the POT1 rs10244817 common variant carriers (OR (95% CI)=1.33 (0.47-3.75), 3.30 (1.14-9.56), respectively) but not among variant genotype carriers (p(interaction)=0.05). Our findings provide evidence that telomere length and genetic variation in telomere maintenance genes may be associated with risk of lung cancer susceptibility and warrant replication in larger studies.

County mortality and cancer incidence in relation to living near two former nuclear materials processing facilities in Pennsylvania--an update

A previous county mortality study of populations living near two nuclear materials processing and fabrication facilities in Westmoreland and Armstrong counties in Pennsylvania (1950-1995) was extended through 2004. Noncancer mortality (1996-2004) and cancer incidence (1990-2004) were also evaluated. Among the Westmoreland and Armstrong populations, 10,547 cancer deaths occurred during the period 1996 through 2004 and the relative risk (RR) based on comparisons with six demographically similar counties in western Pennsylvania was 0.97, that is, almost exactly as expected, and no different from our previously published analyses covering the years 1950-1995. The results based on cancer incidence data were very similar to those based on cancer mortality data. Over the years 1990 though 2004, 39,350 incident cancers were reported among residents of Armstrong and Westmoreland counties and the RR based on the six demographically similar counties was 0.99, that is, almost exactly as expected. The number of deaths from nonmalignant conditions was 36,565 and very close to the number expected (RR 1.01). Overall, no increases in cancer or nonmalignant diseases could be attributed to living in counties with nuclear materials processing and fabrication facilities.