Environmental Factors and Colorectal Tumor Risk in Individuals With Hereditary Nonpolyposis Colorectal Cancer
Authors: Brenda Diergaarde, Hanneke Braam, Hans F. Vasen, Fokko M. Nagengast, Goos N.P. van Muijen, Frans J. Kok, Ellen Kampman
Journal: Clinical Gastroenterology and Hepatology (2007)

Background & Aims: Individuals with hereditary nonpolyposis colorectal cancer (HNPCC) are at increased risk for colorectal cancer. Environmental factors might play a role in HNPCC-associated carcinogenesis. The aim of this study was to gain insight into the effects of environmental factors on colorectal tumor risk in individuals with HNPCC. Methods: We examined associations between dietary factors, cigarette smoking, and HNPCC-associated colorectal tumors in a Dutch case-control study (145 cases, 103 tumor-free controls; all study participants were known or suspected carriers of a germline mutation in one of the DNA mismatch repair genes). We also assessed associations between the various environmental factors and occurrence of adenomatous polyposis coli (APC) mutations in HNPCC-associated polyps in a subset of the study population. Results: Fruit consumption was inversely associated with ever developing HNPCC-associated colorectal tumors (odds ratio [95% confidence interval] for highest vs lowest tertile, 0.4 [0.2–0.9]; Ptrend = .03); a borderline significant inverse association was observed for dietary fiber intake (0.5 [0.2–1.0]; Ptrend = .06). Cigarette smoking seemed to increase the risk of HNPCC-associated colorectal tumors. Truncating APC mutations were detected in 30 (37.5%) of the 80 available HNPCC-associated polyps; frameshift mutations were most common (73.3%). None of the evaluated environmental factors was distinctively associated with a specific APC status of the polyps. Conclusions: Our data suggest that fruit consumption and dietary fiber intake might decrease the risk of colorectal tumors in individuals with HNPCC, whereas cigarette smoking might increase the risk of HNPCC-associated colorectal tumors. The observed associations support the hypothesis that HNPCC-associated outcomes might be modified by environmental factors. Background & Aims: Individuals with hereditary nonpolyposis colorectal cancer (HNPCC) are at increased risk for colorectal cancer. Environmental factors might play a role in HNPCC-associated carcinogenesis. The aim of this study was to gain insight into the effects of environmental factors on colorectal tumor risk in individuals with HNPCC. Methods: We examined associations between dietary factors, cigarette smoking, and HNPCC-associated colorectal tumors in a Dutch case-control study (145 cases, 103 tumor-free controls; all study participants were known or suspected carriers of a germline mutation in one of the DNA mismatch repair genes). We also assessed associations between the various environmental factors and occurrence of adenomatous polyposis coli (APC) mutations in HNPCC-associated polyps in a subset of the study population. Results: Fruit consumption was inversely associated with ever developing HNPCC-associated colorectal tumors (odds ratio [95% confidence interval] for highest vs lowest tertile, 0.4 [0.2–0.9]; Ptrend = .03); a borderline significant inverse association was observed for dietary fiber intake (0.5 [0.2–1.0]; Ptrend = .06). Cigarette smoking seemed to increase the risk of HNPCC-associated colorectal tumors. Truncating APC mutations were detected in 30 (37.5%) of the 80 available HNPCC-associated polyps; frameshift mutations were most common (73.3%). None of the evaluated environmental factors was distinctively associated with a specific APC status of the polyps. Conclusions: Our data suggest that fruit consumption and dietary fiber intake might decrease the risk of colorectal tumors in individuals with HNPCC, whereas cigarette smoking might increase the risk of HNPCC-associated colorectal tumors. The observed associations support the hypothesis that HNPCC-associated outcomes might be modified by environmental factors. Hereditary nonpolyposis colorectal cancer (HNPCC) is one of the most common cancer predisposition syndromes in humans. It is characterized by an autosomal dominant mode of inheritance and an early onset of carcinogenesis (mean age at diagnosis of colorectal cancer, ∼45 years). Colorectal tumors are the predominant form of cancer in HNPCC, but extracolonic cancers, endometrial, ovarian, and stomach cancer in particular, are also often observed.1Marra G. Boland C.R. Hereditary nonpolyposis colorectal cancer: the syndrome, the genes, and historical perspectives.J Natl Cancer Inst. 1995; 87: 1114-1125Crossref PubMed Scopus (482) Google Scholar, 2Lynch H.T. De la Chapelle A. Hereditary colorectal cancer.N Engl J Med. 2003; 348: 919-932Crossref PubMed Scopus (1672) Google Scholar Germline mutations in DNA mismatch repair (MMR) genes are responsible for HNPCC; most (∼90%) have been detected in hMLH1 and hMSH2 (see ICG-HNPCC/INSiGHT mutation database at www.insight-group.org). HNPCC is thought to account for 1%–5% of all colorectal cases,3Rodriguez-Bigas M.A. Boland C.R. Hamilton S.R. et al.A National Cancer Institute work shop on hereditary nonpolyposis colorectal cancer syndrome: meeting highlights and Bethesda guidelines.J Natl Cancer Inst. 1997; 89: 1758-1762Crossref PubMed Scopus (949) Google Scholar, 4Aaltonen L.A. Salovaara R. Kristo P. et al.Incidence of hereditary nonpolyposis colorectal cancer and the feasibility of molecular screening for the disease.N Engl J Med. 1998; 338: 1481-1487Crossref PubMed Scopus (989) Google Scholar, 5Samowitz W. Curtin K. Lin H.H. et al.The colon cancer burden of genetically defined hereditary nonpolyposis colon cancer.Gastroenterology. 2001; 121: 830-838Abstract Full Text Full Text PDF PubMed Scopus (215) Google Scholar, 6Cunningham J.M. Kim C.-Y. Christensen E.R. et al.The frequency of hereditary defective mismatch repair in a prospective series of unselected colorectal carcinomas.Am J Hum Genet. 2001; 69: 780-790Abstract Full Text Full Text PDF PubMed Scopus (294) Google Scholar and mutation carriers might have a lifetime risk of developing colorectal cancer of 60%–80%.7Mitchell R.J. Farrington S.M. Dunlop M.G. et al.Mismatch repair genes hMLH1 and hMSH2 and colorectal cancer: a HuGE review.Am J Epidemiol. 2002; 156: 885-902Crossref PubMed Scopus (119) Google Scholar HNPCC-associated colorectal tumors are often located in the proximal part of the colon, have a more favorable prognosis than sporadic colorectal cancer, and most exhibit microsatellite instability (MSI).1Marra G. Boland C.R. Hereditary nonpolyposis colorectal cancer: the syndrome, the genes, and historical perspectives.J Natl Cancer Inst. 1995; 87: 1114-1125Crossref PubMed Scopus (482) Google Scholar, 2Lynch H.T. De la Chapelle A. Hereditary colorectal cancer.N Engl J Med. 2003; 348: 919-932Crossref PubMed Scopus (1672) Google Scholar Colorectal polyps in individuals with HNPCC progress into cancer more rapidly, within 2–3 years instead of the 10–15 years in the general population, but they do not seem to occur with obviously increased frequency. Several studies have reported the occurrence of inactivating mutations in the adenomatous polyposis coli (APC) tumor suppressor gene in HNPCC-associated colorectal tumors.8Huang J. Papadopoulos N. McKinley A.J. et al.APC mutations in colorectal tumors with mismatch repair deficiency.Proc Natl Acad Sci U S A. 1996; 93: 9049-9054Crossref PubMed Scopus (295) Google Scholar, 9Miyaki M. Iijima T. 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The incomplete penetrance of disease among mutation carriers and the observation that the clinical expression of HNPCC seems to vary between regions and to have changed over time suggest that environmental factors might play a role in HNPCC-associated carcinogenesis.1Marra G. Boland C.R. Hereditary nonpolyposis colorectal cancer: the syndrome, the genes, and historical perspectives.J Natl Cancer Inst. 1995; 87: 1114-1125Crossref PubMed Scopus (482) Google Scholar, 7Mitchell R.J. Farrington S.M. Dunlop M.G. et al.Mismatch repair genes hMLH1 and hMSH2 and colorectal cancer: a HuGE review.Am J Epidemiol. 2002; 156: 885-902Crossref PubMed Scopus (119) Google Scholar, 12Park J.-G. Park Y.J. Wijnen J.T. et al.Gene-environment interaction in hereditary nonpolyposis colorectal cancer with implications for diagnosis and genetic testing.Int J Cancer. 1999; 82: 516-519Crossref PubMed Scopus (64) Google Scholar It is possible that dietary and lifestyle factors known to be relevant in sporadic colorectal carcinogenesis also play a role in HNPCC-associated colorectal cancer; however, epidemiologic data supporting this hypothesis are currently limited. Watson et al13Watson P. Ashwathnarayan R. Lynch H.T. et al.Tobacco use and increased colorectal cancer risk in patients with hereditary nonpolyposis colorectal cancer (Lynch syndrome).Arch Intern Med. 2004; 164: 2429-2431Crossref PubMed Scopus (64) Google Scholar reported a positive association between cigarette smoking and HNPCC-associated colorectal cancer. To our knowledge, the only other study on associations between environmental factors and HNPCC-associated colorectal tumors in humans published to date looked at meat consumption and meat preparation only and observed no clear associations.14Voskuil D.W. Kampman E. Grubben M.J.A.L. et al.Meat consumption and meat preparation in relation to colorectal adenomas among sporadic and HNPCC family patients in the Netherlands.Eur J Cancer. 2002; 38: 2300-2308Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar It has been shown, however, that MMR-deficient cells are more resistant to the cytotoxic effects of various DNA-damaging agents and display a greater increase in induced mutations than MMR-proficient cells.15Glaad W.E. Skopek T.R. Cytotoxic and mutagenic response of mismatch repair- defective human cancer cells exposed to a food-associated heterocyclic amine.Carcinogenesis. 1999; 20: 391-394Crossref PubMed Scopus (21) Google Scholar, 16Glaad W.E. Kort K.L. Skopek T.R. Specificity of mutations induced by the food-associated heterocyclic amine 2-amino-1-1methyl-6-phenylimidazo-[4,5-b]-pyridine in colon cancer cell lines defective in mismatch repair.Cancer Res. 2000; 60: 4921-4925PubMed Google Scholar, 17Glaab W.E. Hill R.B. Skopek T.R. Suppression of spontaneous and hydrogen peroxide-induced mutagenesis by the antioxidant ascorbate in mismatch repair-deficient human colon cancer cells.Carcinogenesis. 2001; 22: 1709-1713Crossref PubMed Scopus (36) Google Scholar The same response to DNA-damaging agents has been observed in MMR-deficient mice.18Wei K. Kucherlapati R. Edelmann W. Mouse models for human DNA mismatch repair gene defects.Trends Mol Med. 2002; 8: 346-352Abstract Full Text Full Text PDF PubMed Scopus (108) Google Scholar The possibility that a simple change in diet and/or lifestyle might result in a decrease in colorectal tumor risk in individuals with HNPCC warrants further investigation, especially because even individuals with HNPCC who are participating in an intensive colorectal surveillance program still seem to have a substantial risk of developing colorectal cancer.19De Vos tot Nederveen Cappel W.H. Nagengast F.M. Griffioen G. et al.Surveillance for hereditary nonpolyposis colorectal cancer.Dis Colon Rectum. 2002; 45: 1588-1594Crossref PubMed Scopus (189) Google Scholar In this study, we examined associations between dietary factors previously reported to be associated with sporadic colorectal cancer risk, cigarette smoking, and development of HNPCC-associated colorectal tumors. APC mutation analysis was performed on polyp tissue from a subset of the study population, and to further explore the relationship between environmental factors and HNPCC-associated colorectal tumors, we also assessed associations between the various dietary factors, cigarette smoking, and the occurrence of truncating APC mutations in HNPCC-associated colorectal polyps. Participants for this case-control study on environmental factors and HNPCC-associated colorectal tumors were recruited in the Netherlands between April 1999–April 2002. All participants belonged to a family fulfilling the Amsterdam criteria for HNPCC20Vasen H.F. Mecklin J.-P. Meera Khan P. et al.The International Collaborative group on Hereditary Nonpolyposis Colorectal Cancer (ICG-HNPCC).Dis Colon Rectum. 1991; 34: 424-425Crossref PubMed Scopus (1755) Google Scholar, 21Vasen H.F. Watson P. Mecklin J.-P. et al.New clinical criteria for hereditary nonpolyposis colorectal cancer (HNPCC, Lynch syndrome) proposed by the International Collaborative group on HNPCC.Gastroenterology. 1999; 116: 1453-1456Abstract Full Text Full Text PDF PubMed Scopus (2104) Google Scholar and were known or suspected carriers of a germline mutation in one of the MMR genes. (Amsterdam criteria: at least 3 relatives with colorectal cancer [Amsterdam criteria I] or another HNPCC-associated cancer [ie, endometrial, stomach, ovary, ureter or renal-pelvis, small bowel, hepatobiliary tract, and sebaceous skin tumors; Amsterdam criteria II], one of whom is a first-degree relative of the other two; at least 2 successive generations are affected; at least one of the relatives is diagnosed with cancer before age 50 years; and familial adenomatous polyposis is excluded.) In addition to this, all participants were Dutch-speaking, white, between 18–75 years old, mentally competent to participate, had no known ulcerative colitis, Crohn's disease, or serious disabling morbidity, and had undergone at least one complete colonoscopy (ie, reaching the cecum). Proven noncarriers and individuals who had undergone a total colectomy were not eligible. In the Netherlands, surveillance recommendations for known and suspected "HNPCC-ers" currently include screening for colorectal tumors by complete colonoscopy at an interval of 2 years or less, starting at 20–25 years of age. Potential study participants were either registered at The Netherlands Foundation for the Detection of Hereditary Tumors (Leiden, The Netherlands), which keeps a registry for Dutch families with HNPCC, or undergoing HNPCC surveillance colonoscopies at the Department of Gastroenterology of UMC St Radboud (Nijmegen, The Netherlands). They were identified by review of randomly selected medical records at the 2 participating sites. After approval of their medical specialist, potential participants were informed about the study by mail. Overall, 84% (n = 312) of the subjects contacted agreed to participate and provided written informed consent. Dietary and lifestyle questionnaires were mailed to those who had agreed to participate. Medical records were checked for information on colonoscopies undergone, history of colorectal cancer and polyps, and other relevant medical history. Case-control status was determined after written informed consent was obtained. If a colorectal polyp(s) had been detected during the last colonoscopy or during a colonoscopy performed maximally 5 years earlier, we tried to obtain the polyp tissue from the pathology departments of the hospitals in which the study participants were under surveillance. Thirty-two (10%) of those who had agreed to participate did not meet the eligibility criteria retrospectively and were therefore excluded from the analyses. In addition, 32 (10%) did not return the questionnaires, leaving a final number of 248 participants with dietary and lifestyle information. Cases (n = 145) were women and men ever diagnosed with colorectal cancer or polyps. Thirty-six (25%) of the cases had ever been diagnosed with colorectal cancer. In total, 119 (82%) cases had at least one polyp diagnosed during their last colonoscopy or during a colonoscopy performed maximally 5 years earlier. But as a result of various reasons (administrative, tissue had been used up by others, tissue had never been stored, etc), polyp tissue from 43 (36%) of those cases was not available to us. Cases whose polyp tissue we did obtain were comparable with cases whose polyp tissue was not available to us (data not shown). The 119 cases diagnosed with a polyp during their last colonoscopy or during a colonoscopy performed maximally 5 years earlier differed significantly from the other 26 cases only in vegetable consumption; mean vegetable intake was lower in the latter group (data not shown). Controls (n = 103) were women and men never diagnosed with colorectal cancer or any kind of colorectal polyp. The average time between enrollment and last colonoscopy was 2.1 ± 1.9 years for cases and 1.9 ± 2.1 years for controls (P = .51). The study protocol was reviewed and approved by the Medical Ethical committees of UMC St Radboud and Wageningen University. Information on lifestyle factors including smoking habits, medical history, reproductive history, physical activity, and family history of colorectal cancer was collected by using a self-administered, structured questionnaire. Regarding smoking habits, information on cigarette smoking status (current, former, never), number of cigarettes usually smoked per day, total number of years smoked, and, if applicable, age at which participant stopped smoking was obtained. Medical records were checked for information on history of colorectal cancer and polyps and other relevant medical history. Usual dietary intake was assessed with a validated, semiquantitative food frequency questionnaire that was originally developed for the Dutch cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC).22Ocké M.C. Bueno de Mesquita H.B. Goddijn H.E. et al.The Dutch EPIC food frequency questionnaire I. Description of the questionnaire, and relative validity and reproducibility for food groups.Int J Epidemiol. 1997; 26: S37-S48Crossref PubMed Google Scholar, 23Ocké M.C. Bueno de Mesquita H.B. Pols M.A. et al.The Dutch EPIC food frequency questionnaire II. Relative validity and reproducibility for nutrients.Int J Epidemiol. 1997; 26: S49-S58Crossref PubMed Google Scholar Briefly, this self-administered questionnaire contained questions on the average consumption frequency during 1 year for 79 main food items. Referent period for the current study was the year preceding inclusion in the study. For 21 foods, the questionnaire contained photographs of 2–4 different sized portions. For most other items the consumption frequency was asked in numbers of specified units (eg, slices or glasses); for a few foods, a standard portion size was assumed. Frequencies per day and portion sizes were multiplied to obtain grams per day for each food item. In total, the average daily consumption of 178 foods was estimated with the information obtained by the questionnaire. Energy and nutrient intakes were calculated by using an adapted version of the computerized Dutch food composition table. When questionnaires were returned incomplete, study staff followed up with the participants by phone. Information on completeness of colonoscopy (ie, whether cecum was reached), location (proximal: cecum through transverse colon; distal: splenic flexure through sigmoid; rectum: first 15 cm from anal opening; colon: exact location unknown), size, number, and type of colorectal tumors detected was obtained from endoscopy and pathology reports. The study pathologist re-evaluated the histology of all colorectal polyps obtained. DNA was extracted from formalin-fixed, paraffin-embedded tissue (10–12 10-μm thick sections) by using the Puregene DNA isolation kit (Gentra Systems, Minneapolis, MN). Polyp tissue was available from 76 cases and also from 11 participants who had agreed to participate and fulfilled all eligibility criteria but did not return the dietary and lifestyle questionnaires. Regarding individuals for whom tissue was available from more than one colorectal polyp (all detected during the same colonoscopy), the largest polyp in size was selected for mutation analysis. Microdissection was performed, guided by a hematoxylin-eosin–stained 4-μm section, and only those areas containing >60% tumor cells were used. Isolated tissue was incubated overnight at 55°C in 500-μL cell lysis solution containing 0.5 mg/mL proteinase K (Roche Diagnostics, Mannheim, Germany), followed by 72 hours at 37°C. Proteins were removed with the protein precipitation solution according to the manufacturer's protocol. DNA was precipitated with 500 μL 100% isopropanol at 4°C for 30 minutes. The pellet was washed with 70% ethanol, air-dried, and subsequently the DNA was rehydrated in 15 μL DNA hydration solution. Codons 1286–1585 of the APC gene (this area includes the mutation cluster region [MCR] in which most somatic inactivating APC mutations have been detected24Miyoshi Y. Nagase H. Ando H. et al.Somatic mutations of the APC gene in colorectal tumors: mutation cluster region in the APC gene.Hum Mol Genet. 1992; 1: 229-233Crossref PubMed Scopus (872) Google Scholar, 25Miyaki M. Konishi M. Kikuchi-Yanoshita R. et al.Characteristics of somatic mutation of the adenomatous polyposis coli gene in colorectal tumors.Cancer Res. 1994; 54: 3011-3020PubMed Google Scholar) were analyzed for truncating mutations (ie, nonsense and frameshift mutations) by direct sequencing. The region was divided into 5 overlapping fragments (codons 1286–1358, 1337–1404, 1387–1455, 1437–1526, and 1509–1585, respectively), which were separately amplified in 2 consecutive polymerase chain reactions (PCRs) as described previously.26Diergaarde B. Van Geloof W.L. Van Muijen G.N.P. et al.Dietary factors and the occurrence of truncating APC mutations in sporadic colon carcinomas: a Dutch population-based study.Carcinogenesis. 2003; 24: 283-290Crossref PubMed Scopus (35) Google Scholar PCR products were checked on an ethidium bromide–stained 2% agarose gel and purified with the QIAquick PCR Purification Kit (Qiagen, Valencia, CA) according to the manufacturer's protocol. Subsequently, the PCR products were sequenced by using ABI PRISM BigDye Terminators v3.0 (Applied Biosystems, Foster City, CA) and cycle sequencing with AmpliTaq DNA polymerase, FS (Applied Biosystems). Sequencing was performed in both directions by using the same primers as in the second PCR. Samples were analyzed on an ABI PRISM 3730 DNA Analyzer (Applied Biosystems). Mutation analysis started in all samples with fragment 1, and only if no truncating mutations were detected was fragment 2 screened for mutations, and so on. We focused on truncating mutations because these mutations indisputably result in function loss of the APC protein, whereas the biologic significance of missense mutations in APC is uncertain. We were unable to perform mutation analysis on 7 polyps (5 from cases and 2 from participants who did not return their questionnaires) because of bad quality DNA and/or insufficient amounts of DNA. Polyps were classified as APC+ (with truncating mutation in APC) or APC− (without truncating mutation in APC and all 5 fragments completely analyzed for mutations). Energy-adjusted nutrient intake was computed with the residual method for women and men separately.27Willett W.C. Howe G.R. Kushi L.H. Adjustment for total energy intake in epidemiologic studies.Am J Clin Nutr. 1997; 65: 1220S-1228SPubMed Scopus (2575) Google Scholar To convey the sense of an actual nutrient intake, we added the mean nutrient intake to each residual.27Willett W.C. Howe G.R. Kushi L.H. Adjustment for total energy intake in epidemiologic studies.Am J Clin Nutr. 1997; 65: 1220S-1228SPubMed Scopus (2575) Google Scholar Differences in characteristics between groups were assessed with t tests for continuous variables and χ2 tests or Fisher exact tests for categorical variables. P values <.05 were considered significant. All significance tests were two-sided. The categorization of the dietary factors in tertiles was based on the distribution of intake in the control population. The interquartile ranges (Q3–Q1), used to quantify associations on a continuous scale, were also based on the distribution of intake in the control population. Cases were compared with the never-affected controls to estimate the relative risk of developing colorectal tumors. Case-control comparisons, separately comparing the APC+-polyp cases and APC−-polyp cases with the controls, were conducted to estimate the relative risk of developing HNPCC-associated polyps with and without truncating APC mutation, respectively. To evaluate heterogeneity in environmental risk factors for the 2 different polyp subsets, APC+ polyp cases were also compared with APC− polyp cases. Odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were calculated by using multiple logistic regression models. For continuous risk factors, linear trend was assessed with the tertile medians as continuous variables in multiple logistic regression models. All analyses were adjusted for age at last colonoscopy (continuously), sex, total energy intake (continuously), carrier status (known carrier, suspected carrier), and cigarette smoking status (never, ever, unknown). Analyses of cigarette smoking were also adjusted for alcohol intake (continuously). Additional adjustment for body mass index (continuously) and other dietary factors (continuously) did not change the estimates by more than 10%, and additional adjustment in the polyp analyses for polyp location (proximal, distal, rectum, colon), polyp size (<5 mm, ≥5 mm), polyp number (single, multiple), and polyp type (hyperplastic, tubular, tubulovillous) did not either. All analyses were performed with the SAS statistical software package (SAS version 8.2; SAS Institute Inc, Cary, NC). Characteristics of the study population are presented in Table 1. In total, the study population consisted of 73 known carriers (hMLH1, 49 [67%]; hMSH2, 22 [30%]; gene not disclosed to us, 2 [3%]). The frequency of known carriers did not differ significantly between cases and controls. Of the cases with unknown carrier status (n = 100), 26 (26%) had been diagnosed with at least one adenomatous polyp before 40 years of age, and 14 (14%) had been diagnosed with colorectal cancer before 50 years of age. Age at last colonoscopy and body mass index were significantly higher among the cases than among the never-affected controls. The case group also contained significantly more ever smokers than the control group. Regarding dietary factors, no marked differences were observed between cases and controls except for alcohol intake, which was significantly higher among cases than among controls.Table 1Characteristics of the Study PopulationControls (n = 103)Cases (n = 145)Known carrier, n (%)28 (27.2)45 (31.0)No. of women (%)57 (55.3)80 (55.2)Age at last colonoscopy, y (mean ± SD)41.1 ± 10.950.0 ± 10.9aP < .05; t tests for continuous and χ2 tests for categorical variables.Age at last colonoscopy, y (range)23–6924–75Body mass index, kg/m2 (mean ± SD)24.3 ± 2.925.1 ± 3.0aP < .05; t tests for continuous and χ2 tests for categorical variables.Total energy intake, kJ/day (mean ± SD)9813.5 ± 3945.79190.8 ± 2550.0Ever smoked,bInformation on smoking status was not available for 9 participants (6 cases; 3 controls). n (%)53 (53.0)99 (71.2)aP < .05; t tests for continuous and χ2 tests for categorical variables.Food groups, g/day (mean ± SD) Total vegetables and fruit295.9 ± 134.1298.0 ± 147.8 Vegetables112.6 ± 40.6113.6 ± 47.0 Fruit183.3 ± 121.8184.4 ± 131.7 Cereals59.5 ± 43.552.3 ± 40.7 Total meat93.6 ± 45.196.3 ± 47.8 Red meat58.4 ± 29.656.3 ± 30.8 Poultry11.8 ± 9.211.5 ± 10.5 Fish10.0 ± 10.010.8 ± 8.5 Dairy products410.8 ± 293.3414.3 ± 279.7Nutrients,cAdjusted for total energy intake by the residual method.g/day (mean ± SD) Alcohol9.8 ± 10.914.0 ± 15.2aP < .05; t tests for continuous and χ2 tests for categorical variables. Fat90.4 ± 17.088.2 ± 16.3 Protein83.7 ± 22.882.6 ± 16.1 Carbohydrates258.4 ± 48.8257.5± 48.3 Dietary fiber25.4 ± 6.024.9 ± 6.2 Calcium (mg/day)1121.5 ± 393.11130.8 ± 363.4 Vitamin C (mg/day)113.5 ± 64.6108.7 ± 46.5 β-carotene (μg/day)1491.1 ± 644.31420.4 ± 478.8 Folate (μg/day)200.5 ± 46.7203.9 ± 43.5SD, standard deviation.a P < .05; t tests for continuous and χ2 tests for categorical variables.b Information on smoking status was not available for 9 participants (6 cases; 3 controls).c Adjusted for total energy intake by the residual method. Open table in a new tab SD, standard deviation. Age was strongly, positively associated with ever been diagnosed with colorectal tumors: OR (95% CI) for ≥45 years at last colonoscopy versus ≤35 years at last colonoscopy, 6.4 (3.0–13.9), and Ptrend < .05 (adjusted for sex, total energy intake, carrier status, and cigarette smoking). No significant association with colorectal tumors was observed for body mass index: OR (95% CI) for >25.5 kg/m2 versus <23.2 kg/m2, 0.9 (0.4–1.8), and Ptrend = .83 (adjusted for age at last colonoscopy, sex, total energy intake, carrier status, and cigarette smoking). Results of case-control comparisons conducted to evaluate associations between dietary factors and risk of developing HNPCC-associated colorectal tumors are presented in Supplementary Table 1; (see supplementary material online at www.cghjournal.org). Consumption of fruits was significantly inversely associated with ever been diagnosed with colorectal tumors (OR[95%CI] for highest vs lowest terti