Repository hosted by TU Delft Library

With the growing number of epidemiologic publications on the relation between dietary factors and cancer risk, pooled analyses that summarize results from multiple studies are becoming more common. Here, the authors describe the methods being used to summarize data on diet-cancer associations within the ongoing Pooling Project of Prospective Studies of Diet and Cancer, begun in 1991. In the Pooling Project, the primary data from prospective cohort studies meeting prespecified inclusion criteria are analyzed using standardized criteria for modeling of exposure, confounding, and outcome variables. In addition to evaluating main exposure-disease associations, analyses are also conducted to evaluate whether exposure-disease associations are modified by other dietary and nondietary factors or vary among population subgroups or particular cancer subtypes. Study-specific relative risks are calculated using the Cox proportional hazards model and then pooled using a random- or mixed-effects model. The study-specific estimates are weighted by the inverse of their variances in forming summary estimates. Most of the methods used in the Pooling Project may be adapted for examining associations with dietary and nondietary factors in pooled analyses of case-control studies or case-control and cohort studies combined. Copyright © 2006 by the Johns Hopkins Bloomberg School of Public Health All rights reserved.

The association between vegetable and fruit consumption and stomach cancer risk was investigated in the Netherlands Cohort Study among 120,852 men and women aged 55-69 years at the start in September 1986. Analyses were based on 282 incident stomach cancer cases after 6.3 years of follow-up. Age- and sex-adjusted rate ratios of stomach cancer in increasing quintiles of combined vegetable and fruit consumption were 1.00, 0.70, 0.65, 0.76, and 0.64 (p trend = 0.04). Multivariate analysis resulted in rate ratios that were somewhat closer to one (p trend = 0.14). Furthermore, inverse associations for total vegetables, pulses, raw leafy vegetables, total fruit, citrus fruit, and apples and pears that were observed in crude analyses became weaker or disappeared in multivariate analyses. Total vegetable, but not fruit, consumption was significantly lower in cases diagnosed in the first follow-up year. In analyses limited to first year cases (resembling a case-control study), rate ratios for increasing tertiles of total vegetable consumption were 1.00, 0.17, and 0.18 (p trend = 0.0001), which may indicate the presence of information bias in case-control studies. This prospective study suggests that vegetable and fruit consumption was not clearly associated with stomach cancer risk in the Dutch population. The findings of this study are comparable with findings of other cohort studies, but they do not support the findings of case-control studies.

The association between 21 vegetables and eight fruits and prostate cancer risk was assessed in the Netherlands Cohort Study among 58,279 men of ages 55-69 years at baseline in 1986. After 6.3 years of follow-up, 610 cases with complete vegetable data and 642 cases with complete fruit data were available for analysis. In multivariate case-cohort analyses, the following rate ratios (RRs) and 95% confidence intervals (CIs) for vegetable consumption were found (comparing highest versus lowest quintile): total vegetables (RR, 0.80; CI, 0.57-1.12); prepared vegetables (RR, 0.85; CI, 0.61-1.19); and raw vegetables (RR, 0.96; CI, 0.69-1.34). For vegetables categorized in botanical groups, no associations were found except for consumption of pulses (RR, 0.71; CI, 0.51-0.98; P for trend, 0.01). The RRs for total fruit and citrus fruit were 1.31 (CI, 0.96-1.79) and 1.27 (CI, 0.93-1.73), respectively; the corresponding Ps for trend were 0.02 and 0.01, respectively. In a continuous model, no association for total fruit was observed. Individual vegetables and fruits were evaluated as continuous variables (g/day). Nonsignificant inverse associations (RRs per increment of 25 g/day) were found for consumption of kale (RR, 0.74), raw endive (RR, 0.72), mandarins (RR, 0.75), and raisins or other dried fruit (RR, 0.49). Observed positive associations were significant for consumption of leek (RR, 1.38) and oranges (RR, 1.07) and nonsignificant for sweet peppers (RR, 1.60) and mushrooms (RR, 1.49). Results in subgroups of cases were more or less consistent with the overall results. From our study, we cannot conclude that vegetable consumption is important in prostate cancer etiology, but for certain vegetables or fruits, an association cannot be excluded.

Doel. Beschrijven van de incidentie van baarmoederhalskanker bij vrouwen in Noord-Holland naar geboorteland. Opzet. Beschrijvend epidemiologisch onderzoek op basis van kankerregistratiegegevens. Methode. Met behulp van de regionale kankerregistratie van het Integraal Kankercentrum Amsterdam (IKA) werd het aantal gevallen van baarmoederhalskanker in Noord-Holland vastgesteld voor de periode 1988-1998. Het waargenomen aantal gevallen (O) werd vergeleken met het aantal dat op basis van de Nederlandse Kankerregistratie kon worden verwacht (E), waarbij een onderverdeling werd gemaakt naar woonplaats (Amsterdam of de rest van Noord-Holland) en naar het geboorteland van de vrouw. Resultaten. In de periode 1988-1998 was de incidentie van baarmoederhalskanker bij vrouwen wonend in Noord-Holland verhoogd ten opzichte van de landelijke incidentie (O/E-ratio: 1,2; 95-BI: 1,1-1,2). De incidentie van baarmoederhalskanker was sterk verhoogd bij vrouwen wonend in Amsterdam (O/E-ratio: 1,5; 95-BI: 1,4-1,6) en bij vrouwen geboren in Marokko (O/E-ratio: 2,1; 95-BI: 1,4-3,1) of Suriname (O/E-ratio: 1,5; 95-BI: 1,1-2,0). Van 10 van de vrouwen was het geboorteland niet te achterhalen. Wat betreft het percentage baarmoederhalskankerpatiënten met uitbreiding van de ziekte buiten de baarmoeder (TNM-stadium II-IV) was er geen verschil tussen allochtone en autochtone vrouwen. Conclusie. Bij vrouwen woonachtig in Amsterdam en vrouwen geboren in Marokko of Suriname was in de periode 1988-1998 de incidentie van baarmoederhalskanker hoger dan gemiddeld in Nederland. Er was geen statistisch significant verschil in stadium bij diagnose tussen allochtone en autochtone vrouwen.

This paper first gives an overview of the epidemiological data concerning the cancer-preventive effect of brassica vegetables, including cabbages, kale, broccoli, Brussels sprouts, and cauliflower. A protective effect of brassicas against cancer may be plausible due to their relatively high content of glucosinolates. Certain hydrolysis products of glucosinolates have shown anticarcinogenic properties. The results of six cohort studies and 74 case-control studies on the association between brassica consumption and cancer risk are summarized. The cohort studies showed inverse associations between the consumption of brassica's and risk of lung cancer, stomach cancer, all cancers taken together. Of the case-control studies 64% showed an inverse association between consumption of one or more brassica vegetables and risk of cancer at various sites. Although the measured effects might have been distorted by various types of bias, it is concluded that a high consumption of brassica vegetables is associated with a decreased risk of cancer. This association appears to be most consistent for lung, stomach, colon and rectal cancer, and least consistent for prostatic, endometrial and ovarian cancer. It is not yet possible to resolve whether associations are to be attributed to brassica vegetables per se or to vegetables in general. Further epidemiological research should separate the anticarcinogenic effect of brassica vegetables from the effect of vegetables in general. The mechanisms by which brassica vegetables might decrease the risk of cancer are reviewed in the second part of this paper. Brassicas, including all types of cabbages, broccoli, cauliflower, and Brussels sprouts, may be protective against cancer due to their glucosinolate content. Glucosinolates are usually broken down through hydrolysis catalysed by myrosinase, an enzyme that is released from damaged plant cells. Some of the hydrolysis products, viz, indoles, and isothiocyanates, are able to influence phase 1 and phase 2 biotransformation enzyme activities, thereby possibly influencing several processes related to chemical carcinogenesis, e.g. the metabolism, DNA-binding, and mutagenic activity of promutagens. Most evidence concerning anticarcinogenic effects of glucosinolate hydrolysis products and brassica vegetables has come from studies in animals. In addition, studies carried out in humans using high but still realistic human consumption levels of indoles and brassica vegetables have shown putative positive effects on health. The combination of epidemiological and experimental data provide suggestive evidence for a cancer preventive effect of a high intake of brassica vegetables. Chemicals/CAS: Anticarcinogenic Agents

Objective: Only a few consistent findings on individual foods or nutrients that influence breast cancer risk have emerged thus far. Since people do not consume individual foods but certain combinations of them, the analysis of dietary patterns may offer an additional aspect for assessing associations between diet and diseases such as breast cancer. It is also important to examine whether the relationships between dietary patterns and breast cancer risk are consistent across populations. Methods: We examined the risk of breast cancer with two dietary patterns, identified as "Vegetables" (VEG) and "Pork, Processed Meat, Potatoes" (PPP), common to all cohorts of the DIETSCAN project. During 7 to 13 years of follow-up, three of the cohorts - the Netherlands Cohort Study on diet and cancer (NLCS), the Swedish Mammography Cohort (SMC), and the Ormoni e Dieta nella Eziologia dei Tumori (Italy-ORDET) - provided data on 3271 breast cancer cases with complete information on their baseline diet measured by a validated food frequency questionnaire. Results: After adjustment for potential confounders, VEG was not associated with the risk of breast cancer across all cohorts. PPP was also not associated with the risk of breast cancer in SMC and ORDET, but a high PPP score tended to be inversely associated with breast cancer in the NLCS study (RR = 0.69; 95% CI, 0.52-0.92, highest versus lowest quartile). PPP differed in one aspect between the cohorts: butter loaded positively on the pattern in all cohorts except NLCS, in which butter loaded negatively and appeared to be substituted by low-fat margarine loading positively. Conclusion: In general, the dietary patterns showed consistent results across the three cohorts except for the possible protective effect of PPP in the NLCS cohort, which could be explained by a difference in that pattern for NLCS. The results supported the suggestion derived from traditional epidemiology that relatively recent diet may not have an important role in the etiology of breast cancer. © Springer 2005.

Background: Dairy foods and their constituents (lactose and calcium) have been hypothesized to promote ovarian carcinogenesis. Although case-control studies have reported conflicting results for dairy foods and lactose, several cohort studies have shown positive associations between skim milk, lactose, and ovarian cancer. Methods: A pooled analysis of the primary data from 12 prospective cohort studies was conducted. The study population consisted of 553,217 women among whom 2,132 epithelial ovarian cases were identified. Study-specific relative risks and 95% confidence intervals were calculated by Cox proportional hazards models and then pooled by a random-effects model. Results: No statistically significant associations were observed between intakes of milk, cheese, yogurt, ice cream, and dietary and total calcium intake and risk of ovarian cancer. Higher lactose intakes comparing ≥30 versus <10 g/d were associated with a statistically significant higher risk of ovarian cancer, although the trend was not statistically significant (pooled multivariate relative risk, 1.19; 95% confidence interval, 1.01-1.40; P trend = 0.19). Associations for endometrioid, mucinous, and serous ovarian cancer were similar to the overall findings. Discussion: Overall, no associations were observed for intakes of specific dairy foods or calcium and ovarian cancer risk. A modest elevation in the risk of ovarian cancer was seen for lactose intake at the level that was equivalent to three or more servings of milk per day. Because a new dietary guideline recommends two to three servings of dairy products per day, the relation between dairy product consumption and ovarian cancer risk at these consumption levels deserves further examination. Copyright © 2006 American Association for Cancer Research.

Objective: To investigate baseline fat intake and the risk of colon and rectal tumors lacking MLH1 (mutL homolog 1, colon cancer, nonpolyposis type 2) repair gene expression and harboring mutations in the APC (adenomatous polyposis coli) tumor suppressor gene and in the KRAS (v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) oncogene. Methods: After 7.3 years of follow-up of the Netherlands Cohort Study (n = 120,852), adjusted incidence rate ratios (RR) and 95% confidence intervals (CI) were computed, based on 401 colon and 130 rectal cancer patients. Results: Total, saturated and monounsaturated fat were not associated with the risk of colon or rectal cancer, or different molecular subgroups. There was also no association between polyunsaturated fat and the risk of overall or subgroups of rectal cancer. Linoleic acid, the most abundant polyunsaturated fatty acid in the diet, was associated with increased risk of colon tumors with only a KRAS mutation and no additional truncating APC mutation or lack of MLH1 expression (RR = 1.41, 95% CI 1.18-1.69 for one standard deviation (i.e., 7.5 g/day) increase in intake, p-trend over the quartiles of intake <0.001). Linoleic acid intake was not associated with risk of colon tumors without any of the gene defects, or with tumors harboring aberrations in either MLH1 or APC. Conclusion: Linoleic acid intake is associated with colon tumors with an aberrant KRAS gene, but an intact APC gene and MLH1 expression, suggesting a unique etiology of tumors with specific genetic aberrations. © 2007 Springer Science + Business Media B.V.

Objective: The aim of this study was to investigate the associations between meat and fish consumption and APC mutation status and hMLH1 expression in colon and rectal cancer. Methods: The associations were investigated in the Netherlands Cohort Study, and included 434 colon and 154 rectal cancer patients on whom case-cohort analyses (subcohort n = 2948) were performed. Results: Total meat consumption was not associated with the endpoints studied. Meat product (i.e. processed meat) consumption showed a positive association with colon tumours harbouring a truncating APC mutation, whereas beef consumption was associated with an increased risk of colon tumours without a truncating APC mutation (incidence rate ratio (RR) highest versus lowest quartile of intake 1.61, 95% confidence interval (CI) 0.96-2.71, p-trend = 0.04 and 1.58, 95% CI 1.10-2.25, p-trend = 0.01, respectively). Consumption of other meat (horsemeat, lamb, mutton, frankfurters and deep-fried meat rolls) was associated with an increased risk of rectal cancer without a truncating APC mutation (RR intake versus no intake 1.79, 95% CI 1.10-2.90). No associations were observed for meat consumption and tumours lacking hMLH1 expression. Conclusions: Our data indicate that several types of meat may contribute differently to the aetiology of colon and rectal cancer, depending on APC mutation status but not hMLH1 expression of the tumour. © Springer 2005.