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Iron homeostasis and distal colorectal adenoma risk in the prostate, lung, colorectal, and ovarian cancer screening trial.

ABSTRACT: Red meat consumption has been positively associated with colorectal cancer; however, the biological mechanism underlying this relationship is not understood. Red meat is a major source of iron, which may play a role in colorectal carcinogenesis via increased crypt cell proliferation, cytotoxicity, and endogenous N-nitrosation. In a nested case-control study within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, we prospectively evaluated multiple iron exposure parameters, including dietary intake and serum measures of iron, ferritin, transferrin, total iron binding capacity (TIBC), and unsaturated iron binding capacity (UIBC) in relation to incident colorectal adenoma in 356 cases and 396 matched polyp-free controls. We also investigated variation in eight key genes involved in iron homeostasis in relation to colorectal adenoma in an additional series totaling 1,126 cases and 1,173 matched controls. We observed a positive association between red meat intake and colorectal adenoma [OR comparing extreme quartiles (OR(q4-q1)) = 1.59, 95% CI = 1.02-2.49, P(trend) = 0.03]. Serum TIBC and UIBC were inversely associated with colorectal adenoma (OR(q4-q1) = 0.57, 95% CI = 0.37-0.88, P(trend) = 0.03; and OR(q4-q1) = 0.62, 95% CI = 0.40-0.95, P(trend) = 0.04, respectively). Colorectal adenoma was not associated with serum ferritin, iron, or transferrin saturation or with polymorphisms in genes involved in iron homeostasis. Serum TIBC and UIBC, parameters that have a reciprocal relationship with overall iron load, were inversely related to colorectal adenoma, suggesting that individuals with lower iron status have a reduced risk of developing colorectal adenoma.

SUBMITTER: Cross AJ

PROVIDER: S-EPMC3168068 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Iron homeostasis and distal colorectal adenoma risk in the prostate, lung, colorectal, and ovarian cancer screening trial.

Cross Amanda J AJ Sinha Rashmi R Wood Richard J RJ Xue Xiaonan X Huang Wen-Yi WY Yeager Meredith M Hayes Richard B RB Gunter Marc J MJ

Cancer prevention research (Philadelphia, Pa.) 20110617 9

Red meat consumption has been positively associated with colorectal cancer; however, the biological mechanism underlying this relationship is not understood. Red meat is a major source of iron, which may play a role in colorectal carcinogenesis via increased crypt cell proliferation, cytotoxicity, and endogenous N-nitrosation. In a nested case-control study within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, we prospectively evaluated multiple iron exposure parameters, inc ...[more]

PMID: 21685236

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Project description:Dietary fiber has been associated with a reduced risk of colorectal cancer. However, it remains unclear at which stage in the carcinogenic pathway fiber may act or which food sources of dietary fiber may be most beneficial against colorectal cancer development.The objective was to prospectively evaluate the association between dietary fiber intake and the risk of incident and recurrent colorectal adenoma and incident colorectal cancer.Study participants were identified from the intervention arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Participants received flexible sigmoidoscopy at baseline and 3 or 5 y after. Dietary fiber intake was measured by using a self-reported dietary questionnaire. The colorectal cancer, incident adenoma, and recurrent adenoma analyses were based on 57,774, 16,980, and 1667 participants, respectively. Unconditional logistic regression was used to assess the risk of incident and recurrent adenoma, and Cox proportional hazards models were used to assess the risk of colorectal cancer across categories of dietary fiber intake, with adjustment for potential confounders.Elevated total dietary fiber intake was associated with a significantly reduced risk of incident distal colorectal adenoma (ORhighest vs. lowest tertile of intake: 0.76; 95% CI: 0.63, 0.91; P-trend = 0.003) but not recurrent adenoma (P-trend = 0.67). Although the association was not statistically significant for colorectal cancer overall (HR: 0.85; 95% CI: 0.70, 1.03; P-trend = 0.10), a reduced risk of distal colon cancer was observed with increased total fiber intake (HR: 0.62; 95% CI: 0.41, 0.94; P-trend = 0.03). Protective associations were most notable for fiber originating from cereals or fruit.This large, prospective study within a population-based screening trial suggests that individuals consuming the highest intakes of dietary fiber have reduced risks of incident colorectal adenoma and distal colon cancer and that this effect of dietary fiber, particularly from cereals and fruit, may begin early in colorectal carcinogenesis. This trial was registered at clinicaltrials.gov as NCT01696981.

Project description:BackgroundThe 5-year overall survival rate of lung cancer patients is approximately 15%. Most patients are diagnosed with advanced-stage disease and have shorter survival rates than patients with early-stage disease. Although screening for lung cancer has the potential to increase early diagnosis, it has not been shown to reduce lung cancer mortality rates. In 1993, the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial was initiated specifically to determine whether screening would reduce mortality rates from PLCO cancers.MethodsA total of 77 464 participants, aged 55-74 years, were randomly assigned to the intervention arm of the PLCO Cancer Screening Trial between November 8, 1993, and July 2, 2001. Participants received a baseline chest radiograph (CXR), followed by three annual single-view CXRs at the 10 US screening centers. Cancers were classified as screen detected and nonscreen detected (interval or never screened) and according to tumor histology. The positivity rates of screen-detected cancers and positive predictive values (PPVs) were calculated. Because 51.6% of the participants were current or former smokers, logistic regression analysis was performed to control for smoking status. All statistical tests were two-sided.ResultsCompliance with screening decreased from 86.6% at baseline to 78.9% at the last screening. Overall positivity rates were 8.9% at baseline and 6.6%-7.1% at subsequent screenings; positivity rates increased modestly with smoking risk categories (P(trend) < .001). The PPVs for all participants were 2.0% at baseline and 1.1%, 1.5%, and 2.4% at years 1, 2, and 3, respectively; PPVs in current smokers were 5.9% at baseline and 3.3%, 4.2%, and 5.6% at years 1, 2, and 3, respectively. A total of 564 lung cancers were diagnosed, of which 306 (54%) were screen-detected cancers and 87% were non-small cell lung cancers. Among non-small cell lung cancers, 59.6% of screen-detected cancers and 33.3% of interval cancers were early (I-II) stage.ConclusionsThe PLCO Cancer Screening Trial demonstrated the ability to recruit, retain, and screen a large population over multiple years at multiple centers. A higher proportion of screen-detected lung cancers were early stage, but a conclusion on the effectiveness of CXR screening must await final PLCO results, which are anticipated at the end of 2015.

Project description:IntroductionIdentification of individuals at high risk for lung cancer should be of value to individuals, patients, clinicians, and researchers. Existing prediction models have only modest capabilities to classify persons at risk accurately.MethodsProspective data from 70 962 control subjects in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) were used in models for the general population (model 1) and for a subcohort of ever-smokers (N = 38 254) (model 2). Both models included age, socioeconomic status (education), body mass index, family history of lung cancer, chronic obstructive pulmonary disease, recent chest x-ray, smoking status (never, former, or current), pack-years smoked, and smoking duration. Model 2 also included smoking quit-time (time in years since ever-smokers permanently quit smoking). External validation was performed with 44 223 PLCO intervention arm participants who completed a supplemental questionnaire and were subsequently followed. Known available risk factors were included in logistic regression models. Bootstrap optimism-corrected estimates of predictive performance were calculated (internal validation). Nonlinear relationships for age, pack-years smoked, smoking duration, and quit-time were modeled using restricted cubic splines. All reported P values are two-sided.ResultsDuring follow-up (median 9.2 years) of the control arm subjects, 1040 lung cancers occurred. During follow-up of the external validation sample (median 3.0 years), 213 lung cancers occurred. For models 1 and 2, bootstrap optimism-corrected receiver operator characteristic area under the curves were 0.857 and 0.805, and calibration slopes (model-predicted probabilities vs observed probabilities) were 0.987 and 0.979, respectively. In the external validation sample, models 1 and 2 had area under the curves of 0.841 and 0.784, respectively. These models had high discrimination in women, men, whites, and nonwhites.ConclusionThe PLCO lung cancer risk models demonstrate high discrimination and calibration.

Project description:Non-steroidal anti-inflammatory drugs (NSAIDs) have been documented in animal and human studies to reduce risk for colorectal cancer and adenomatous polyps, but risk modification for subgroups of the population and effects on hyperplastic polyps have been less studied.Data on recent use of two frequently ingested NSAIDs, aspirin and ibuprofen, were collected at baseline from participants aged 55-74 years in the 10 centers of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO). Participants randomized to the intervention arm of the trial received a flexible sigmoidoscopy during a baseline examination. Follow-up of detected polyps was accomplished outside the Trial setting and relevant records were sought and abstracted. Cases (n=4,017) included subjects with a biopsy-proven polyp in the left side of the colon (descending colon, sigmoid, and rectum) detected as a consequence of PLCO screening; controls (n=38,396) were subjects with no left-sided colon polyp.Regular use of aspirin (≥ 4 times/month) in the past year was inversely associated with hyperplastic polyps (odds ratios (OR)=0.8, 95% confidence interval (CI)=0.7-0.9), adenomatous polyps (OR=0.8, 95% CI=0.8-0.9), and advanced adenomas (OR=0.8, 95% CI=0.7-0.9). As frequency of aspirin use increased, the prevalence of polyps decreased significantly for each histological classification (P for trend ≤ 0.0004). Similar patterns were found for adenomas and ibuprofen. Overall protection was consistent in both the descending colon or sigmoid and the rectum, but more evident in males. In males, the OR for heavy use of combined aspirin and ibuprofen (≥ 2 times/day) was 0.6 (95% CI=0.5-0.8), as opposed to 0.9 (95% CI=0.8-1.1) in females. The protective effects of NSAIDs for females were apparent only among those with body mass index (BMI) <25 (OR=0.8, 95% CI=0.7-1.0 for regular use of NSAIDs; P interaction=0.04). We also found a slightly stronger protection of NSAIDs in the 70-74 years age group compared with those aged 55-69 years.This study of a large general risk population supports previous work that recent use of aspirin and ibuprofen is associated with a decreased risk of colorectal adenomas and demonstrates that this protective effect may be stronger in certain population subgroups and is also evident for aspirin and hyperplastic polyps.

Project description:BackgroundThe impact of lung cancer screening on smoking behavior is unclear. The aims of this ancillary study of the Prostate Lung Colorectal and Ovarian Cancer Screening Trial were to produce risk prediction models to identify individuals at risk of relapse or continued smoking and to evaluate whether cancer-screening variables affect long-term smoking outcomes.MethodsParticipants completed a baseline questionnaire at trial enrollment and a supplemental questionnaire 4-14 years after enrollment, which assessed several cancer-related variables, including family history of cancer, comorbidities, and tobacco use. Multivariable logistic regression models were used to predict smoking status at completion of the supplemental questionnaire. The models' predictive performances were evaluated by assessing discrimination via the receiver operator characteristic area under the curve (ROC AUC) and calibration. Models were internally validated using bootstrap methods.ResultsOf the 31&emsp14;694 former smokers on the baseline questionnaire, 1042 (3.3%) had relapsed (ie, reported being a current smoker on the supplemental questionnaire). Of the 6807 current smokers on the baseline questionnaire, 4439 (65.2%) reported continued smoking on the supplemental questionnaire. Relapse was associated with multiple demographic, medical, and tobacco-related characteristics. This model had a bootstrap median ROC AUC of 0.862 (95% confidence interval [CI] = 0.858 to 0.866) and a calibration slope of 1.004 (95% CI = 0.978 to 1.029), indicating excellent discrimination and calibration. Predictors of continued smoking also included multiple demographic, medical, and tobacco-related characteristics. This model had an ROC AUC of 0.611 (95% CI = 0.605 to 0.614) and a slope of 1.006 (95% CI = 0.962 to 1.041), indicating modest discrimination. Neither the trial arm nor the lung-screening result was statistically significantly associated with smoking outcomes.ConclusionThese models, if validated externally, may have public health utility in identifying individuals at risk for adverse smoking outcomes, who may benefit from relapse prevention and smoking cessation interventions.

Dataset Information

Iron homeostasis and distal colorectal adenoma risk in the prostate, lung, colorectal, and ovarian cancer screening trial.

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Iron homeostasis and distal colorectal adenoma risk in the prostate, lung, colorectal, and ovarian cancer screening trial.

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