The age-dependent association of risk factors with pancreatic cancer

BACKGROUND

Pancreatic cancer presents as advanced disease in >80% of patients; yet, appropriate ages to consider prevention and early detection strategies are poorly defined. We investigated age-specific associations and attributable risks of pancreatic cancer for established modifiable and non-modifiable risk factors.

PATIENTS AND METHODS

We included 167 483 participants from two prospective US cohort studies with 1190 incident cases of pancreatic cancer during >30 years of follow-up; 5107 pancreatic cancer cases and 8845 control participants of European ancestry from a completed multicenter genome-wide association study (GWAS); and 248 893 pancreatic cancer cases documented in the US Surveillance, Epidemiology, and End Results (SEER) Program. Across different age categories, we investigated cigarette smoking, obesity, diabetes, height, and non-O blood group in the prospective cohorts; weighted polygenic risk score of 22 previously identified single nucleotide polymorphisms in the GWAS; and male sex and black race in the SEER Program.

RESULTS

In the prospective cohorts, all five risk factors were more strongly associated with pancreatic cancer risk among younger participants, with associations attenuated among those aged >70 years. The hazard ratios comparing participants with three to five risk factors with those with no risk factors were 9.24 [95% confidence interval (CI) 4.11-20.77] among those aged ≤60 years, 3.00 (95% CI 1.85-4.86) among those aged 61-70 years, and 1.46 (95% CI 1.10-1.94) among those aged >70 years (Pheterogeneity = 3×10-5). These factors together were related to 65.6%, 49.7%, and 17.2% of incident pancreatic cancers in these age groups, respectively. In the GWAS and the SEER Program, the associations with the polygenic risk score, male sex, and black race were all stronger among younger individuals (Pheterogeneity ≤0.01).

CONCLUSIONS

Established risk factors are more strongly associated with earlier-onset pancreatic cancer, emphasizing the importance of age at initiation for cancer prevention and control programs targeting this highly lethal malignancy.

Mendelian Randomization Analysis of n-6 Polyunsaturated Fatty Acid Levels and Pancreatic Cancer Risk

BACKGROUND

Whether circulating polyunsaturated fatty acid (PUFA) levels are associated with pancreatic cancer risk is uncertain. Mendelian randomization (MR) represents a study design using genetic instruments to better characterize the relationship between exposure and outcome.

METHODS

We utilized data from genome-wide association studies within the Pancreatic Cancer Cohort Consortium and Pancreatic Cancer Case-Control Consortium, involving approximately 9,269 cases and 12,530 controls of European descent, to evaluate associations between pancreatic cancer risk and genetically predicted plasma n-6 PUFA levels. Conventional MR analyses were performed using individual-level and summary-level data.

RESULTS

Using genetic instruments, we did not find evidence of associations between genetically predicted plasma n-6 PUFA levels and pancreatic cancer risk [estimates per one SD increase in each PUFA-specific weighted genetic score using summary statistics: linoleic acid odds ratio (OR) = 1.00, 95% confidence interval (CI) = 0.98-1.02; arachidonic acid OR = 1.00, 95% CI = 0.99-1.01; and dihomo-gamma-linolenic acid OR = 0.95, 95% CI = 0.87-1.02]. The OR estimates remained virtually unchanged after adjustment for covariates, using individual-level data or summary statistics, or stratification by age and sex.

CONCLUSIONS

Our results suggest that variations of genetically determined plasma n-6 PUFA levels are not associated with pancreatic cancer risk.

IMPACT

These results suggest that modifying n-6 PUFA levels through food sources or supplementation may not influence risk of pancreatic cancer.

Assessment of polygenic architecture and risk prediction based on common variants across fourteen cancers

Genome-wide association studies (GWAS) have led to the identification of hundreds of susceptibility loci across cancers, but the impact of further studies remains uncertain. Here we analyse summary-level data from GWAS of European ancestry across fourteen cancer sites to estimate the number of common susceptibility variants (polygenicity) and underlying effect-size distribution. All cancers show a high degree of polygenicity, involving at a minimum of thousands of loci. We project that sample sizes required to explain 80% of GWAS heritability vary from 60,000 cases for testicular to over 1,000,000 cases for lung cancer. The maximum relative risk achievable for subjects at the 99th risk percentile of underlying polygenic risk scores (PRS), compared to average risk, ranges from 12 for testicular to 2.5 for ovarian cancer. We show that PRS have potential for risk stratification for cancers of breast, colon and prostate, but less so for others because of modest heritability and lower incidence.

A prospective study of coffee intake and pancreatic cancer: results from the NIH-AARP Diet and Health Study

BACKGROUND

Evidence evaluating the association between type of coffee intake (caffeinated, decaffeinated) and risk of pancreatic cancer is limited.

METHODS

In the US NIH-AARP Diet and Health Study, we used Cox proportional hazards regression to estimate hazard ratios and 95% confidence intervals (CIs) for coffee intake and risk of pancreatic cancer among 457 366 US adults.

RESULTS

Over 4 155 256 person-years of follow-up, 1541 incident first primary pancreatic cancers occurred. Following detailed adjustment for tobacco smoking history, risk estimates for coffee drinking were not statistically significant; compared with never drinkers of coffee, the hazard ratios (95% CI) were 1.05 (0.85-1.30), 1.06 (0.86-1.31), 1.03 (0.85-1.25), 1.00 (0.79-1.25), and 1.24 (0.93-1.65) for <1, 1, 2-3, 4-5, and ≥6 cups per day, respectively (P-value for trend 0.46). The observed null association was consistent across all examined strata (sex, smoking status, coffee caffeination, and prevalent diabetes).

CONCLUSIONS

In a prospective study of coffee intake with the largest number of pancreatic cancer cases to date, we did not observe an association between total, caffeinated, or decaffeinated coffee intake and pancreatic cancer.

Central adiposity, obesity during early adulthood, and pancreatic cancer mortality in a pooled analysis of cohort studies

BACKGROUND

Body mass index (BMI), a measure of obesity typically assessed in middle age or later, is known to be positively associated with pancreatic cancer. However, little evidence exists regarding the influence of central adiposity, a high BMI during early adulthood, and weight gain after early adulthood on pancreatic cancer risk.

DESIGN

We conducted a pooled analysis of individual-level data from 20 prospective cohort studies in the National Cancer Institute BMI and Mortality Cohort Consortium to examine the association of pancreatic cancer mortality with measures of central adiposity (e.g. waist circumference; n = 647 478; 1947 pancreatic cancer deaths), BMI during early adulthood (ages 18-21 years) and BMI change between early adulthood and cohort enrollment, mostly in middle age or later (n = 1 096 492; 3223 pancreatic cancer deaths). Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards regression models.

RESULTS

Higher waist-to-hip ratio (HR = 1.09, 95% CI 1.02-1.17 per 0.1 increment) and waist circumference (HR = 1.07, 95% CI 1.00-1.14 per 10 cm) were associated with increased risk of pancreatic cancer mortality, even when adjusted for BMI at baseline. BMI during early adulthood was associated with increased pancreatic cancer mortality (HR = 1.18, 95% CI 1.11-1.25 per 5 kg/m(2)), with increased risk observed in both overweight and obese individuals (compared with BMI of 21.0 to <23 kg/m(2), HR = 1.36, 95% CI 1.20-1.55 for BMI 25.0 < 27.5 kg/m(2), HR = 1.48, 95% CI 1.20-1.84 for BMI 27.5 to <30 kg/m(2), HR = 1.43, 95% CI 1.11-1.85 for BMI ≥30 kg/m(2)). BMI gain after early adulthood, adjusted for early adult BMI, was less strongly associated with pancreatic cancer mortality (HR = 1.05, 95% CI 1.01-1.10 per 5 kg/m(2)).

CONCLUSIONS

Our results support an association between pancreatic cancer mortality and central obesity, independent of BMI, and also suggest that being overweight or obese during early adulthood may be important in influencing pancreatic cancer mortality risk later in life.

Dairy products and pancreatic cancer risk: a pooled analysis of 14 cohort studies

Pancreatic cancer has few early symptoms, is usually diagnosed at late stages, and has a high case-fatality rate. Identifying modifiable risk factors is crucial to reducing pancreatic cancer morbidity and mortality. Prior studies have suggested that specific foods and nutrients, such as dairy products and constituents, may play a role in pancreatic carcinogenesis. In this pooled analysis of the primary data from 14 prospective cohort studies, 2212 incident pancreatic cancer cases were identified during follow-up among 862 680 individuals. Adjusting for smoking habits, personal history of diabetes, alcohol intake, body mass index (BMI), and energy intake, multivariable study-specific hazard ratios (MVHR) and 95% confidence intervals (CIs) were calculated using the Cox proportional hazards models and then pooled using a random effects model. There was no association between total milk intake and pancreatic cancer risk (MVHR = 0.98, 95% CI = 0.82-1.18 comparing ≥500 with 1-69.9 g/day). Similarly, intakes of low-fat milk, whole milk, cheese, cottage cheese, yogurt, and ice-cream were not associated with pancreatic cancer risk. No statistically significant association was observed between dietary (MVHR = 0.96, 95% CI = 0.77-1.19) and total calcium (MVHR = 0.89, 95% CI = 0.71-1.12) intake and pancreatic cancer risk overall when comparing intakes ≥1300 with <500 mg/day. In addition, null associations were observed for dietary and total vitamin D intake and pancreatic cancer risk. Findings were consistent within sex, smoking status, and BMI strata or when the case definition was limited to pancreatic adenocarcinoma. Overall, these findings do not support the hypothesis that consumption of dairy foods, calcium, or vitamin D during adulthood is associated with pancreatic cancer risk.

Flavonoid intake and risk of pancreatic cancer in the National Institutes of Health-AARP Diet and Health Study Cohort

Background:

Limited epidemiological studies show inverse associations between dietary flavonoid intake and pancreatic cancer risk, but results are inconsistent and are based on few cases. We examined the association between intake of flavonoids and pancreatic cancer risk in the large, prospective National Institutes of Health-AARP Diet and Health Study Cohort.

Methods:

During follow-up through 2006 (median follow-up 10.6 years), 2379 pancreatic cancer cases were identified. We used Cox proportional hazards modelling to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

Results:

We found no association between total flavonoid intake (Q5 vs Q1 HR=1.09, 95% CI: 0.96–1.24) or any flavonoid subtypes and pancreatic cancer risk. Significant interactions were not observed by age, sex, smoking status, BMI or diabetes.

Conclusion:

Our results do not support the hypothesis that flavonoids have a protective role in pancreatic cancer carcinogenesis.

Is dietary fat, vitamin D, or folate associated with pancreatic cancer?

Although potentially modifiable risk factors for pancreatic cancer include smoking, obesity, and diabetes, less is known about the extent to which diet affects cancer risk. Recent studies have demonstrated some consistency for dietary fat being associated with elevated pancreatic cancer risk, particularly from animal sources. However, less is known about which fatty acids pose the greatest risk. Vitamin D, due to its endogenous production following UV-B exposure, is a unique risk factor in that researchers have created several methods to assess its exposure in humans. Studies that measured vitamin D exposure differently have shown inconsistent results. Dietary studies suggest protective associations, whereas studies of circulating 25-hydroxyvitamin D status show null or positive associations with low or very high concentrations, respectively. Several, but not all epidemiologic studies provide evidence of an inverse relationship between total and/or dietary folate and risk of pancreatic cancer. Protective associations for circulating folate are more often observed among populations with inadequate status. This article reviews the current epidemiological and experimental evidence investigating the relationship of dietary fat, vitamin D, and folate with pancreatic cancer. Additionally the mechanisms by which these risk factors may contribute to cancer, the methodological challenges involved with assessing risk, and other obstacles encountered when ascertaining the magnitude and direction of these three exposures are discussed.

Predictors of vitamin D biochemical status in a large sample of middle-aged male smokers in Finland

BACKGROUND/OBJECTIVES

As vitamin D deficiency is considered to be more common in regions with little solar ultraviolet (UV) light in winter, the aim of this study was to analyze predictors of vitamin D status by season within a large sample of male smokers from Finland, a country where there is negligible solar UV light in winter.

SUBJECTS/METHODS

Vitamin D (measured by 25-hydroxyvitamin D (25(OH)D) nmol/l) and other serum constituents were assayed. Measured anthropometry, and self-reported dietary intake and physical activity (PA) were obtained and analyzed using stepwise multiple linear and logistic regression in 2271 middle-aged Finnish male smokers.

RESULTS

In all, 27% of the population in winter and 17% in summer had serum 25(OH)D levels of <25 nmol/l, respectively. In summer, in multiple logistic regression analyses with adjustment for confounding and other predictors, high vitamin D intake (odds ratios (OR) 3.6; 95% confidence interval (CI) 1.5-8.5), some leisure time PA (OR 2.0; 95% CI 1.3-3.1) and having a body mass index (BMI) of >or=21 kg/m(2) compared with <21 kg/m(2) (OR 2.6; 95% CI 1.3-5.0), were associated with 25(OH)D >or=25 nmol/l. In winter, additional modifiable factors were occupational PA (OR 1.6; 95% CI 1.1-2.5) and high fish (OR 3.1; 95% CI 1.7-6.2) or poultry consumption (OR 1.7; 95% CI 1.2-2.5). Predictors from linear regression analyses of continuous levels of 25(OH)D were similar to the logistic regression analyses of 25(OH)D >or=25 nmol/l.

CONCLUSION

In this Finnish sample more vitamin D intake, PA and having a BMI of >or=21 may have important modifiable roles in maintaining an adequate vitamin D status.

Alcohol intake and risk of thyroid cancer in the NIH-AARP Diet and Health Study

Background:

Certain studies suggest that alcohol may reduce the risk of thyroid cancer in women, but the effect in men remains unclear.

Methods:

We analysed the association between alcohol and thyroid cancer in a large (n=490 159) prospective NIH-AARP Diet and Health Study with self-reported beer, wine, and liquor intakes.

Results:

Over 7.5 years of follow-up (median), 170 men and 200 women developed thyroid cancer. Overall, the thyroid cancer risk decreased with greater alcohol consumption (⩾2 drinks per day vs none, relative risk=0.57, 95% CI 0.36–0.89, P-trend=0.01).

Conclusions:

These results suggest a potential protective role for alcohol consumption in thyroid cancer.

Review and pooled analysis of studies on MTHFR C677T polymorphism and esophageal cancer

Esophageal cancer has been associated with tobacco and alcohol consumption, gastric reflux, exposure to nitrosamines from food or other environmental sources, and diets lacking folate. Susceptibility to esophageal cancer may be modified by functional polymorphisms in genes along the folate metabolic pathway, such as methylenetetrahydrofolate reductase (MTHFR). The C677T polymorphism is the most common functional variant, leading to a reduction in enzyme activity. We report a pooled analysis of 5 studies on the association of MTHFR C677T polymorphism and esophageal cancer, including 725 cases and 1531 controls. A significant association between the MTHFR 677 TT genotype and esophageal cancer was observed (OR=2.63, 95% CI: 1.75-3.94), although there was significant heterogeneity between studies. A sensitivity analysis excluded one study; the association between TT genotype and esophageal cancer was still present, although of reduced magnitude (OR=1.57, 95% CI: 0.96-2.56). A significant interaction between smoking and TT genotype on esophageal cancer risk was observed, while no interaction was observed between alcohol consumption and genotype.

Helicobacter pylori seropositivity as a risk factor for pancreatic cancer

BACKGROUND

Pancreatic cancer is among the most fatal cancers worldwide and one for which few preventable risk factors have been established. Gastric carriage of Helicobacter pylori, particularly cytotoxin-associated gene-A-positive (CagA+) strains, is known to be a risk factor for peptic ulcer disease and gastric cancer and may have a similar etiologic relationship with pancreatic cancer.

METHODS

We investigated the association of H. pylori carriage and exocrine pancreatic cancer in a nested case-control study within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort of 29 133 male Finnish smokers aged 50-69 years at baseline. Case subjects (n = 121) were matched on date of baseline serum collection, study center, age, trial intervention, and completion of the dietary questionnaire to 226 control subjects who were alive at the time the matching case subject was diagnosed and who remained free of cancer, during up to 10 years of follow-up. Levels of immunoglobulin G antibodies to H. pylori whole-cell and CagA+ antigens from stored baseline serum were measured by enzyme-linked immunosorbent assay. Smoking-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by use of conditional logistic regression. Statistical tests were two-sided.

RESULTS

Seroprevalence of H. pylori was 82% and 73% among case and control subjects, respectively. Compared with seronegative subjects, those with H. pylori or CagA+ strains were at statistically significantly elevated risk of pancreatic cancer (OR = 1.87 [95% CI = 1.05 to 3.34]; OR = 2.01 [95% CI = 1.09 to 3.70], respectively).

CONCLUSIONS

Our findings support a possible role for H. pylori carriage in the development of exocrine pancreatic cancer.

Dietary and other methyl-group availability factors and pancreatic cancer risk in a cohort of male smokers

The authors examined prospectively whether dietary folate and other factors known to influence methyl-group availability were associated with the development of exocrine pancreatic cancer within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort. Of the 27,101 healthy male smokers aged 50--69 years who completed a self-administered dietary questionnaire at baseline, 157 developed pancreatic cancer during up to 13 years of follow-up from 1985 to 1997. Cox proportional hazards models were used to estimate the hazards ratios and 95% confidence intervals. The adjusted hazards ratio comparing the highest with the lowest quintile of dietary folate intake was 0.52 (95% confidence interval: 0.31, 0.87; p-trend = 0.05). Dietary methionine, alcohol intake, and smoking history did not modify this relation. No significant associations were observed between dietary methionine, vitamins B(6) and B(12), or alcohol intake and pancreatic cancer risk. Consistent with prior studies, this study shows that cigarette smoking was associated with an increased risk (highest compared with lowest quintile, cigarettes per day: hazards ratio = 1.82; 95% confidence interval: 1.10, 3.03; p-trend = 0.05). These results support the hypothesis that dietary folate intake is inversely associated with the risk of pancreatic cancer and confirm the risk associated with greater cigarette smoking.

The effects of supplementation with alpha-tocopherol and beta-carotene on the incidence and mortality of carcinoma of the pancreas in a randomized, controlled trial

BACKGROUND

Dietary components may be both causal and protective in cases of pancreatic carcinoma, but the preventive potential of single constituents has not been evaluated. The authors report the effects of alpha-tocopherol and beta-carotene supplementations on the rates of incidence of and mortality from pancreatic carcinoma in a randomized, controlled trial.

METHODS

The 29,133 participants in the Alpha-Tocopherol Beta-Carotene Cancer Prevention (ATBC) Study were male smokers who were ages 50-69 years at the time they were randomized into 1 of the following 4 intervention groups: dl-alpha-tocopherol (AT; 50 mg/day), beta-carotene (BC; 20 mg/day), both AT and BC, and placebo. The daily supplementation lasted for 5-8 years. Incident cancers were identified through the national Finnish Cancer Registry and death certificates of the Statistics Finland. Results were analyzed by supplementation with Cox regression models.

RESULTS

Effects of both supplementations were statistically nonsignificant. The rate of incidence of pancreatic carcinoma was 25% lower for the men who received beta-carotene supplements (n = 38) compared with the rate for those who did not receive beta-carotene (n = 51) (95% CI, -51% to 14%). Supplementation with alpha-tocopherol (n = 51) increased the rate of incidence by 34% (95% CI, -12% to 105%) compared with the rate for those who did not receive alpha-tocopherol. Mortality from pancreatic carcinoma during the follow-up, adjusted for stage and anatomic location of the tumor, was 19% (95% CI, -47% to 26%) lower among those who received beta-carotene and 11% (95% CI, -28% to 72%) higher among those who received alpha-tocopherol as compared with those who did not receive supplementation.

CONCLUSIONS

Supplementation with beta-carotene or alpha-tocopherol does not have a statistically significant effect on the rate of incidence of pancreatic carcinoma or the rate of mortality caused by this disease.

Pancreatic cancer risk and nutrition-related methyl-group availability indicators in male smokers

BACKGROUND

Few risk factors for pancreatic cancer have been identified, with age and cigarette smoking being the most consistent. The protective effect associated with consumption of fruits and vegetables-the major dietary sources of folate-is suggestive of a role for factors influencing cellular methylation reactions; however, to our knowledge, no study has investigated this relationship. Whether biochemical indicators of methyl-group availability are associated with exocrine pancreatic cancer risk was the focus of this investigation.

METHODS

We conducted a nested case-control study within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort of 29133 male Finnish smokers aged 50-69 years. One hundred twenty-six subjects with incident exocrine pancreatic cancer were matched by date of baseline blood draw (+/-30 days), study center, age (+/-5 years), trial intervention group, and completion of dietary history to 247 control subjects, who were alive and free from cancer at the time the case subjects were diagnosed. Odds ratios (ORs) and 95% confidence intervals (CIs) were determined by use of conditional logistic regression. Reported P values are two-tailed.

RESULTS

Serum folate and pyridoxal-5'-phosphate (PLP) concentrations showed statistically significant inverse dose-response relationships with pancreatic cancer risk, with the highest serum tertiles having approximately half the risk of the lowest (folate: OR = 0.45; 95% CI = 0.24-0.82; P for trend = .009, and PLP: OR = 0.48; 95% CI = 0.26-0.88; P for trend = .02). An increased pancreatic cancer risk was also observed with greater exposure to cigarettes (e.g., pack-years [number of packs smoked per day x number of years of smoking], highest versus lowest quartile: OR = 2.13; 95% CI = 1.13-3.99; P for trend = .04).

CONCLUSIONS

These results support the hypothesis that maintaining adequate folate and pyridoxine status may reduce the risk of pancreatic cancer and confirm the risk previously associated with cigarette smoking.

Association of dietary protein intake and coffee consumption with serum homocysteine concentrations in an older population

BACKGROUND

Elevated blood concentrations of total homocysteine (tHcy) have been implicated in the pathogenesis of atherosclerotic cardiovascular disease. Previous studies identified suboptimal nutritional status and dietary intake of folate, vitamin B-6, and vitamin B-12 as determinants of elevated tHcy.

OBJECTIVE

We identified other nutritional factors associated with tHcy in 260 retired schoolteachers in the Baltimore metropolitan area.

DESIGN

We performed observational analyses of baseline and 2-4-mo follow-up data collected in a study designed to test the feasibility of conducting a large-scale clinical trial of vitamin supplements by mail. The study population consisted of 151 women and 109 men with a median age of 64 y. At baseline, each participant completed a food-frequency questionnaire. At follow-up, fasting serum tHcy was measured.

RESULTS

In multivariable linear regression and generalized linear models, there was an independent, inverse dose-response relation between dietary protein and In tHcy (P = 0.002) and a positive, significant dose-response relation between coffee consumption and In tHcy (P for trend = 0.01). Other significant predictors of In tHcy were creatinine (positive; P = 0.0001) and prestudy use of supplemental B vitamins (inverse; P = 0.03). In stratified analyses restricted to persons receiving standard multivitamin therapy, the association of 1n tHcy with dietary protein and coffee persisted.

CONCLUSIONS

These results support the hypothesis that increased protein intake and decreased coffee consumption may reduce tHcy and potentially prevent atherosclerotic cardiovascular disease and other disease outcomes.