D. S. M. Chan

Body mass index and survival in women with breast cancer—systematic literature review and meta-analysis of 82 follow-up studies

The current systematic literature review and meta-analysis extends and confirms the associations of obesity with an unfavourable overall and breast cancer survival in pre and postmenopausal breast cancer, regardless of when BMI is ascertained. Increased risks of mortality in underweight and overweight women and J-shape associations with total mortality were also observed. The recommendation of maintaining a healthy body weight throughout life is important as obesity is a pandemic health concern.

Dairy products and colorectal cancer risk: a systematic review and meta-analysis of cohort studies

BACKGROUND Previous studies of the association between intake of dairy products and colorectal cancer risk have indicated an inverse association with milk, however, the evidence for cheese or other dairy products is inconsistent. METHODS We conducted a systematic review and meta-analysis to clarify the shape of the dose-response relationship between dairy products and colorectal cancer risk. We searched the PubMed database for prospective studies published up to May 2010. Summary relative risks (RRs) were estimated using a random effects model. RESULTS Nineteen cohort studies were included. The summary RR was 0.83 (95% CI [confidence interval]: 0.78-0.88, I2=25%) per 400 g/day of total dairy products, 0.91 (95% CI: 0.85-0.94, I2=0%) per 200 g/day of milk intake and 0.96 (95% CI: 0.83-1.12, I2=28%) per 50 g/day of cheese. Inverse associations were observed in both men and women but were restricted to colon cancer. There was evidence of a nonlinear association between milk and total dairy products and colorectal cancer risk, P<0.001, and the inverse associations appeared to be the strongest at the higher range of intake. CONCLUSION This meta-analysis shows that milk and total dairy products, but not cheese or other dairy products, are associated with a reduction in colorectal cancer risk.BACKGROUND Previous studies of the association between intake of dairy products and colorectal cancer risk have indicated an inverse association with milk, however, the evidence for cheese or other dairy products is inconsistent. METHODS We conducted a systematic review and meta-analysis to clarify the shape of the dose-response relationship between dairy products and colorectal cancer risk. We searched the PubMed database for prospective studies published up to May 2010. Summary relative risks (RRs) were estimated using a random effects model. RESULTS Nineteen cohort studies were included. The summary RR was 0.83 (95% CI [confidence interval]: 0.78-0.88, I2 = 25%) per 400 g/day of total dairy products, 0.91 (95% CI: 0.85-0.94, I2 = 0%) per 200 g/day of milk intake and 0.96 (95% CI: 0.83-1.12, I2 = 28%) per 50 g/day of cheese. Inverse associations were observed in both men and women but were restricted to colon cancer. There was evidence of a nonlinear association between milk and total dairy products and colorectal cancer risk, P < 0.001, and the inverse associations appeared to be the strongest at the higher range of intake. CONCLUSIONS This meta-analysis shows that milk and total dairy products, but not cheese or other dairy products, are associated with a reduction in colorectal cancer risk.

Meta-analyses of vitamin D intake, 25-hydroxyvitamin D status, vitamin D receptor polymorphisms and colorectal cancer risk

Background: Our objective was to conduct a systematic review and meta-analysis of prospective studies on colorectal cancer (CRC) and vitamin D intake and 25-hydroxyvitamin D status, as part of the World Cancer Research Fund Continuous Update Project. We also aimed at conducting meta-analysis of all studies on CRC and vitamin D receptor (VDR) single-nucleotide polymorphisms. Methods: Relevant studies were identified in PubMed (up to June 2010). Inclusion criteria were original and peer-reviewed publications with a prospective design (for studies on vitamin D intake or status). Random effects of dose-response meta-analyses were performed on cancer incidence. Results: We observed inverse associations of CRC risk with dietary vitamin D [summary relative risk (RR) per 100 IU/day = 0.95, 95% CI: 0.93–0.98; 10 studies; range of intake (midpoints) = 39–719 IU/day] and serum/plasma 25-hydroxyvitamin D (RR per 100 IU/L = 0.96, 0.94–0.97; 6 studies; range = 200–1,800 IU/L), but not with total vitamin D (5 studies). Supplemental (2 studies; range = 0–600 IU/day) and total (4 studies; range = 79–732 IU/day) vitamin D intake and 25-hydroxyvitamin D status (6 studies; range = 200–1,800 IU/L) were inversely associated with colon cancer risk. We did not observe statistically significant associations between FokI, PolyA, TaqI, Cdx2, and ApaI VDR polymorphisms and CRC risk. The BsmI polymorphism was associated with a lower CRC risk (RR = 0.57, 0.36–0.89 for BB versus bb, 8 studies). Conclusions: These meta-analyses support the evidence of an inverse association between vitamin D intake, 25-hydroxyvitamin D status, and the BsmI VDR polymorphism and CRC risk. Impact: Improving vitamin D status could be potentially beneficial against CRC incidence. Cancer Epidemiol Biomarkers Prev; 20(5); 1003–16. ©2011 AACR.

Dietary fiber and breast cancer risk: a systematic review and meta-analysis of prospective studies

BACKGROUND Evidence from case-control studies suggest that dietary fiber may be inversely related to breast cancer risk, but it is unclear if this is supported by prospective data. We conducted a systematic review and meta-analysis of the evidence from prospective studies. METHODS PubMed was searched for prospective studies of fiber intake and breast cancer risk until 31st August 2011. Random effects models were used to estimate summary relative risks (RRs). RESULTS Sixteen prospective studies were included. The summary RR for the highest versus the lowest intake was 0.93 [95% confidence interval (CI) 0.89-0.98, I(2) = 0%] for dietary fiber, 0.95 (95% CI 0.86-1.06, I(2) = 4%) for fruit fiber, 0.99 (95% CI 0.92-1.07, I(2) = 1%) for vegetable fiber, 0.96 (95% CI 0.90-1.02, I(2) = 5%) for cereal fiber, 0.91 (95% CI 0.84-0.99, I(2) = 7%) for soluble fiber and 0.95 (95% CI 0.89-1.02, I(2) = 0%) for insoluble fiber. The summary RR per 10 g/day of dietary fiber was 0.95 (95% CI 0.91-0.98, I(2) = 0%, P(heterogeneity) = 0.82). In stratified analyses, the inverse association was only observed among studies with a large range (≥13 g/day) or high level of intake (≥25 g/day). CONCLUSION In this meta-analysis of prospective studies, there was an inverse association between dietary fiber intake and breast cancer risk.

Dairy products, calcium, and prostate cancer risk: a systematic review and meta-analysis of cohort studies

BACKGROUND Dairy product and calcium intakes have been associated with increased prostate cancer risk, but whether specific dairy products or calcium sources are associated with risk is unclear. OBJECTIVE In the Continuous Update Project, we conducted a meta-analysis of prospective studies on intakes of dairy products and calcium and prostate cancer risk. DESIGN PubMed and several other databases were searched up to April 2013. Summary RRs were estimated by using a random-effects model. RESULTS Thirty-two studies were included. Intakes of total dairy products [summary RR: 1.07 (95% CI: 1.02, 1.12; n = 15) per 400 g/d], total milk [summary RR: 1.03 (95% CI: 1.00, 1.07; n = 14) per 200 g/d], low-fat milk [summary RR: 1.06 (95% CI: 1.01, 1.11; n = 6) per 200 g/d], cheese [summary RR: 1.09 (95% CI: 1.02, 1.18; n = 11) per 50 g/d], and dietary calcium [summary RR: 1.05 (95% CI: 1.02, 1.09; n = 15) per 400 mg/d] were associated with increased total prostate cancer risk. Total calcium and dairy calcium intakes, but not nondairy calcium or supplemental calcium intakes, were also positively associated with total prostate cancer risk. Supplemental calcium was associated with increased risk of fatal prostate cancer. CONCLUSIONS High intakes of dairy products, milk, low-fat milk, cheese, and total, dietary, and dairy calcium, but not supplemental or nondairy calcium, may increase total prostate cancer risk. The diverging results for types of dairy products and sources of calcium suggest that other components of dairy rather than fat and calcium may increase prostate cancer risk. Any additional studies should report detailed results for subtypes of prostate cancer.

Dietary compared with blood concentrations of carotenoids and breast cancer risk: a systematic review and meta-analysis of prospective studies

BACKGROUND Measurement errors in the dietary assessment of fruit and vegetable intake may attenuate associations with breast cancer risk and might explain the weak associations observed in epidemiologic studies. Carotenoid concentrations in blood are biomarkers of fruit and vegetable intake; however, no systematic assessment has compared dietary intake with blood concentrations of carotenoids and breast cancer risk. OBJECTIVE We conducted a systematic review and meta-analysis of prospective studies of dietary intake and blood concentrations of carotenoids and breast cancer risk. DESIGN We searched PubMed and several other databases for relevant studies up to 31 August 2011. Random-effects models were used to estimate summary estimates. RESULTS Of the 6 dietary carotenoids assessed, only intake of β-carotene was significantly associated with a reduced breast cancer risk (summary RR: 0.95; 95% CI: 0.91, 0.99; I(2): 0%) per 5000 μg/d (n = 10). In contrast, the summary RR for blood concentrations of carotenoids was 0.78 (95% CI: 0.61, 0.99; I(2): 53%) per 100 μg total carotenoids/dL (n = 7), 0.74 (95% CI: 0.57, 0.97; I(2): 43%) per 50 μg β-carotene/dL (n = 13), 0.82 (95% CI: 0.73, 0.92, I(2): 3%) per 10 μg α-carotene/dL (n = 12), and 0.68 (95% CI: 0.52, 0.89; I(2): 0%) per 25 μg lutein/dL (n = 6). CONCLUSIONS Blood concentrations of carotenoids are more strongly associated with reduced breast cancer risk than are carotenoids assessed by dietary questionnaires. Our results suggest that the use of certain biomarkers may clarify inconsistent and weak results between dietary intake and breast cancer risk.

Anthropometric factors and endometrial cancer risk: A systematic review and dose-response meta-analysis of prospective studies

BACKGROUND Greater body mass index (BMI) has been convincingly related to increased endometrial cancer risk, however, whether adiposity earlier in life or abdominal fatness is an independent risk factor and whether weight gain or greater height increases the risk is not clear. METHODS As part of the Continuous Update Project of the World Cancer Research Fund International, we conducted a systematic review and meta-analysis of prospective studies of the association between anthropometric measures and endometrial cancer risk and searched PubMed and several other databases up to February 2015. Summary relative risks (RRs) were calculated using a random-effects model. RESULTS Thirty prospective studies of BMI and endometrial cancer risk with 22 320 cases among 6 445 402 participants were included. The summary RR for a 5-unit increment was 1.54 [95% confidence interval (CI) 1.47-1.61, I(2) = 81%]. Although the test for non-linearity was significant, Pnon-linearity < 0.0001, and the curve was steeper within the overweight and obese BMI ranges, there was evidence of increased risk even within the high normal BMI range. The summary RR was 1.45 (95% CI 1.28-1.64, I(2) = 76%) per 5 BMI units for BMI in young adulthood, 1.18 (95% CI 1.14-1.23, I(2) = 67%) per 5 kg increase of weight, and 1.16 (95% CI 1.12-1.20, I(2) = 51%) per 5 kg of weight gained between young adulthood and study baseline, 1.27 (95% CI 1.17-1.39, I(2) = 71%) per 10 cm increase in waist circumference, 1.21 (95% CI 1.13-1.29, I(2) = 0%) per 0.1-unit increment in waist-to-hip ratio and 1.30 (95% CI 1.19-1.41, I(2) = 0%) per 10-cm increase in hips circumference. The summary RR was 1.15 (95% CI 1.09-1.22, I(2) = 61%) for a 10-cm increase in height. CONCLUSIONS All measures of adiposity were associated with increased risk of endometrial cancer, and in addition increasing height was associated with increased risk.

Fruits, vegetables and lung cancer risk: a systematic review and meta-analysis

BACKGROUND Lung cancer is the most common cause of cancer death. Fruits and vegetables containing carotenoids and other antioxidants have been hypothesized to decrease lung cancer risk. As part of the World Cancer Research Fund International Continuous Update Project, we conducted a systematic review and meta-analysis of prospective studies. METHODS We searched PubMed and several databases up to December 2014 for prospective studies. We conducted meta-analyses comparing the highest and lowest intakes and dose-response meta-analyses to estimate summary relative risks (RRs) and 95% confidence intervals (CIs), and examine possible non-linear associations. We combined results from the Pooling Project with the studies we identified to increase the statistical power of our analysis. RESULTS When comparing the highest with the lowest intakes, the summary RR estimates were 0.86 [95% CI 0.78-0.94; n (studies) = 18] for fruits and vegetables, 0.92 (95% CI 0.87-0.97; n = 25) for vegetables and 0.82 (95% CI 0.76-0.89; n = 29) for fruits. The association with fruit and vegetable intake was marginally significant in current smokers and inverse but not significant in former or never smokers. Significant inverse dose-response associations were observed for each 100 g/day increase: for fruits and vegetables [RR: 0.96; 95% CI 0.94-0.98, I(2) = 64%, n = 14, N (cases) = 9609], vegetables (RR: 0.94; 95% CI 0.89-0.98, I(2) = 48%, n = 20, N = 12 563) and fruits (RR: 0.92; 95% CI 0.89-0.95, I(2) = 57%, n = 23, N = 14 506). Our results were consistent among the different types of fruits and vegetables. The strength of the association differed across locations. There was evidence of a non-linear relationship (P < 0.01) between fruit and vegetable intake and lung cancer risk showing that no further benefit is obtained when increasing consumption above ∼400 g per day. CONCLUSIONS Eliminating tobacco smoking is the best strategy to prevent lung cancer. Although residual confounding by smoking cannot be ruled out, the current evidence from prospective studies is consistent with a protective role of fruit and vegetables in lung cancer aetiology.

Dietary carbohydrates, glycemic index, glycemic load and endometrial cancer risk: a systematic review and meta-analysis of prospective studies

Endometrial cancer is the 5 th most common cancer among women worldwide with 287 000 new cases diagnosed in 2008, accounting for 4.8% of all female cancer cases (1) . Insulin resistance may play a role in the etiology of endometrial cancer based on the observation that several risk factors for endometrial cancer including adiposity (2) , low physical activity (2) , elevated levels of blood glucose (3) and C-peptide (4) , and diabetes (5) are linked to insulin resistance. Carbohydrates are the main dietary component affecting an individual’s insulin secretion, therefore glycemic response is also relevant in this topic (6) . Both glycemic index (GI) and glycemic load (GL) are used to rank foods according to their effects on blood glucose concentration. High GI and GL have been associated with increased risk of type 2 diabetes, obesity, and metabolic syndrome in several studies (6) . The objective of this study was to review and quantitatively summarize in a meta-analysis the evidence for an association between GI, GL and carbohydrates intake with the incidence of endometrial cancer in prospective cohort studies. PubMed database was searched for prospective studies of carbohydrates intake, GI, and GL and endometrial cancer risk, up to December 2011. A pre-specified protocol, which includes details of the search terms used, for the review was followed (http:// www.dietandcancerreport.org/cancer_resource_center/cup_protocols.php). We computed 95 % Confidence Intervals (CIs) from the natural logs of the Relative Risks (RRs) and CIs across categories of carbohydrate, and GI and GL intake. Overall RRs were estimated by use of a random effects model. Six cohort studies met the eligibility criteria for inclusion in the meta-analysis of carbohydrates, GI, GL and endometrial cancer risk. The summary RR for high vs. low intake was 1.17 (95 % CI: 1.03‐1.34) for carbohydrate intake, 1.00 (95 % CI: 0.87‐1.14) for GI, and 1.22 (95 % CI: 1.09‐1.37) for GL. In the dose-response analysis the summary RR was 1.18 (95 % CI: 1.02‐1.37) per 100 grams of carbohydrates per day and 1.15 (95% CI: 1.06‐1.25) per 50 GL units. The summary RR was 1.21 (95 % CI: 1.05‐1.38) for high vs. low total sugar intake and 1.07 (95% CI: 1.01‐1.13) per 25 g/d. In this meta-analysis of prospective studies we found that a higher intake of carbohydrates, as well as a high GL were predictors of an increased risk of endometrial cancer. There was no evidence of an association between endometrial cancer and GI. Our results provide further support for the hypothesis that dietary carbohydrate, glycemic load and total sugars may increase the risk of endometrial cancer.