Lifestyle factors and colorectal cancer risk (2): a systematic review and meta-analysis of associations with leisure-time physical activity

The association between physical activity and renal cancer: systematic review and meta-analysis

Background:

Physical activity may decrease renal cancer risk by reducing obesity, blood pressure, insulin resistance, and lipid peroxidation. Despite plausible biologic mechanisms linking increased physical activity to decreased risk for renal cancer, few epidemiologic studies have been able to report a clear inverse association between physical activity and renal cancer, and no meta-analysis is available on the topic.

Methods:

We searched the literature using PubMed and Web of Knowledge to identify published non-ecologic epidemiologic studies quantifying the relationship between physical activity and renal cancer risk in individuals without a cancer history. Following the PRISMA guidelines, we conducted a systematic review and meta-analysis, including information from 19 studies based on a total of 2 327 322 subjects and 10 756 cases. The methodologic quality of the studies was examined using a comprehensive scoring system.

Results:

Comparing high vs low levels of physical activity, we observed an inverse association between physical activity and renal cancer risk (summary relative risk (RR) from random-effects meta-analysis=0.88; 95% confidence interval (CI)=0.79–0.97). Summarising risk estimates from high-quality studies strengthened the inverse association between physical activity and renal cancer risk (RR=0.78; 95% CI=0.66–0.92). Effect modification by adiposity, hypertension, type 2 diabetes, smoking, gender, or geographic region was not observed.

Conclusion:

Our comprehensive meta-analysis provides strong support for an inverse relation of physical activity to renal cancer risk. Future high-quality studies are required to discern which specific types, intensities, frequencies, and durations of physical activity are needed for renal cancer risk reduction.

Diet and colorectal cancer risk and survival

SUMMARY Unhealthy dietary and other lifestyle factors account for 20–45% of all colorectal cancer cases. Being overweight or obese, having a high intake of red and processed meat and alcohol increase the risk of colorectal cancer, while a high intake of dairy products, fruits and vegetables, foods containing dietary fiber and being physically active lower the risk of colorectal cancer. There are only a limited number of studies available on diet and outcomes in colorectal cancer survivors. Most of these studies are retrospective in nature, and are small in size, which makes it difficult to draw conclusions. However, the available studies to date putatively suggest that lifestyle factors lowering the risk of colorectal cancer are also beneficial for cancer survivors.

Job strain as a risk factor for leisure-time physical inactivity: an individual-participant meta-analysis of up to 170,000 men and women: the IPD-Work Consortium

Unfavorable work characteristics, such as low job control and too high or too low job demands, have been suggested to increase the likelihood of physical inactivity during leisure time, but this has not been verified in large-scale studies. The authors combined individual-level data from 14 European cohort studies (baseline years from 1985–1988 to 2006–2008) to examine the association between unfavorable work characteristics and leisure-time physical inactivity in a total of 170,162 employees (50% women; mean age, 43.5 years). Of these employees, 56,735 were reexamined after 2–9 years. In cross-sectional analyses, the odds for physical inactivity were 26% higher (odds ratio = 1.26, 95% confidence interval: 1.15, 1.38) for employees with high-strain jobs (low control/high demands) and 21% higher (odds ratio = 1.21, 95% confidence interval: 1.11, 1.31) for those with passive jobs (low control/low demands) compared with employees in low-strain jobs (high control/low demands). In prospective analyses restricted to physically active participants, the odds of becoming physically inactive during follow-up were 21% and 20% higher for those with high-strain (odds ratio = 1.21, 95% confidence interval: 1.11, 1.32) and passive (odds ratio = 1.20, 95% confidence interval: 1.11, 1.30) jobs at baseline. These data suggest that unfavorable work characteristics may have a spillover effect on leisure-time physical activity.

Risk factors for young-onset colorectal cancer

PURPOSE

We investigated risk factors for colorectal cancer in early-onset cancers, to provide quantitative estimates for major selected risk factors.

METHODS

We analyzed data from three Italian and Swiss case-control studies conducted between 1985 and 2009, including 329 colorectal cancer cases and 1,361 controls aged ≤45 years. We computed odds ratios (ORs) from unconditional logistic regression models, adjusted for major confounding factors.

RESULTS

The OR of young-onset colorectal cancer was 4.50 for family history of colorectal cancer in first-degree relatives, the association being higher in subjects with affected siblings (OR 11.68) than parents (OR 3.75). The ORs of young-onset colorectal cancer were 1.56 for ≥14 drinks/week of alcohol, 1.56 for the highest tertile of processed meat, 0.40 for vegetables, 0.75 for fruit, and 0.78 for fish intake. Among micronutrients, the ORs were 0.52 for β-carotene, 0.68 for vitamin C, 0.38 for vitamin E, and 0.59 for folate. No significant associations emerged for physical activity, overweight, and diabetes.

CONCLUSIONS

This study-the largest on young-onset colorectal cancer-confirms that several recognized risk factors for colorectal cancer are also relevant determinants of young-onset colorectal cancer. Family history of colorectal cancer in particular is a stronger risk factor in young subjects, as compared to middle age and elderly ones.

Glycaemic index and glycaemic load in relation to risk of diabetes-related cancers: a meta-analysis

Diets high in glycaemic index (GI) or glycaemic load (GL) have been hypothesised to increase the risks of certain cancers by increasing blood glucose or insulin concentrations. We aimed to conduct a meta-analysis of prospective cohort studies to evaluate the association between GI or GL and diabetes-related cancers (DRC), including bladder, breast, colon-rectum, endometrium, liver and pancreas, which are associated with an increased risk for diabetes, and prostate cancer, which is associated with a reduced risk for diabetes. We searched Pubmed, EMBASE and MEDLINE databases up to September 2011 and reference lists of relevant articles. Relative risks (RR) and 95 % CI for the highest v. the lowest categories were extracted and pooled using a random-effects model. Thirty-six prospective cohort studies with a total of 60 811 DRC cases were included in the present meta-analysis. In a comparison of the highest and lowest categories, the pooled RR of DRC were 1·07 (95 % CI 1·04, 1·11; n 30) for GI and 1·02 (95 % CI 0·96, 1·08; n 33) for GL. In an analysis of site-specific cancer risks, we found significant associations for GI in relation to breast cancer (RR 1·06; 95 % CI 1·02, 1·11; n 11) and colorectal cancer (RR 1·08; 95 % CI 1·00, 1·17; n 9 studies). GL was significantly associated with the risk of endometrial cancer (RR 1·21; 95 % CI 1·07, 1·37; n 5). In conclusion, the findings of the present study suggest a modest-to-weak association between a diet that induces a high glucose response and DRC risks.

Prediction of Colorectal Cancer Risk Using a Genetic Risk Score: The Korean Cancer Prevention Study-II (KCPS-II)

Colorectal cancer (CRC) is among the leading causes of cancer deaths and can be caused by environmental factors as well as genetic factors. Therefore, we developed a prediction model of CRC using genetic risk scores (GRS) and evaluated the effects of conventional risk factors, including family history of CRC, in combination with GRS on the risk of CRC in Koreans. This study included 187 cases (men, 133; women, 54) and 976 controls (men, 554; women, 422). GRS were calculated with most significantly associated single-nucleotide polymorphism with CRC through a genomewide association study. The area under the curve (AUC) increased by 0.5% to 5.2% when either counted or weighted GRS was added to a prediction model consisting of age alone (AUC 0.687 for men, 0.598 for women) or age and family history of CRC (AUC 0.692 for men, 0.603 for women) for both men and women. Furthermore, the risk of CRC significantly increased for individuals with a family history of CRC in the highest quartile of GRS when compared to subjects without a family history of CRC in the lowest quartile of GRS (counted GRS odds ratio [OR], 47.9; 95% confidence interval [CI], 4.9 to 471.8 for men; OR, 22.3; 95% CI, 1.4 to 344.2 for women) (weighted GRS OR, 35.9; 95% CI, 5.9 to 218.2 for men; OR, 18.1, 95% CI, 3.7 to 88.1 for women). Our findings suggest that in Koreans, especially in Korean men, GRS improve the prediction of CRC when considered in conjunction with age and family history of CRC.

Autophagy modulation as a potential therapeutic target for diverse diseases

Autophagy is an essential, conserved lysosomal degradation pathway that controls the quality of the cytoplasm by eliminating protein aggregates and damaged organelles. It begins when double-membraned autophagosomes engulf portions of the cytoplasm, which is followed by fusion of these vesicles with lysosomes and degradation of the autophagic contents. In addition to its vital homeostatic role, this degradation pathway is involved in various human disorders, including metabolic conditions, neurodegenerative diseases, cancers and infectious diseases. This article provides an overview of the mechanisms and regulation of autophagy, the role of this pathway in disease and strategies for therapeutic modulation.

Colorectal cancer screening and physical activity promotion among obese women: an online evaluation of targeted messages

Obese women are at higher risk for several cancers, but are less likely than normal weight women to engage in cancer prevention behaviors such as screening and physical activity. Targeted health messages may help increase healthy behaviors among vulnerable groups such as obese women. Using findings from focus groups with obese women, the authors created targeted messages to promote colorectal cancer screening and physical activity among obese women. The messages addressed psychosocial constructs, such as benefits and barriers to colorectal cancer screening and exercise, which were relevant to the target population. Messages were tested online with women age 50 years and older (N = 181). Participants were stratified by weight (obese vs. nonobese) and randomized to review either 10 targeted (intervention) or 10 generic (control) messages. Study outcomes included elaboration about the messages, message relevance and trustworthiness, and behavioral intentions. The authors used moderation and subgroup analyses to determine whether the intervention messages were better received by certain women. They found no differences in elaboration, behavioral intentions, relevance, or trustworthiness between intervention and control for either weight group. However, exercise intentions increased more (p = .06) among inactive obese women who received intervention messages (+2.9) compared with those who were in the control group (+1.2). Intervention messages also produced more elaboration among women who viewed their weight as a barrier to screening or exercise. Tailoring intervention messages for obese women on the basis of behavior and barriers may improve outcomes more than giving the same messages to all obese women.

Menopausal hormone therapy and risk of gastrointestinal cancer: nested case-control study within a prospective cohort, and meta-analysis

Use of menopausal hormone therapy (HT) has been associated with reduced risk of colorectal cancer; evidence for its effect on other gastrointestinal cancers is limited. We conducted a nested case-control study within a UK cohort, and meta-analyses combining our results with those from published studies. Our study included women aged 50+ in the UK General Practice Research Database (GPRD): 1,054 with oesophageal, 750 with gastric and 4,708 with colorectal cancer, and 5 age- and practice-matched controls per case. Relative risks (RRs) and 95% confidence intervals (CIs) for cancer in relation to prospectively-recorded HT prescriptions were estimated by conditional logistic regression. Women prescribed HT had a reduced risk of oesophageal cancer (adjusted RR for 1+ vs. no HT prescriptions, 0.68, 95% CI 0.53-0.88; p = 0.004), gastric cancer (0.75, 0.54-1.05; p = 0.1) and colorectal cancer (0.81, 0.73-0.90; p < 0.001). There were no significant differences in cancer risk by HT type, estimated duration of HT use or between past and current users. In meta-analyses, risks for ever vs. never use of HT were significantly reduced for all three cancers (summary RR for oesophageal cancer, 0.68, 0.55-0.84, p < 0.001; for gastric cancer, 0.78, 0.65-0.94, p = 0.008; for colorectal cancer, 0.84, 0.81-0.88, p < 0.001). In high-income countries, estimated incidence over 5 years of these three cancers combined in women aged 50-64 was 2.9/1,000 in HT users and 3.6/1,000 in never users. The absolute reduction in risk of these cancers in HT users is small compared to the HT-associated increased risk of breast cancer.

Subsite-specific colorectal cancer risk in the colorectal endoscopy era

BACKGROUND

Colorectal endoscopy (sigmoidoscopy and colonoscopy) is thought to reduce colorectal cancer (CRC) risk. Since the 1980s, its use has increased in the United States, which may be a reason for decreasing CRC incidence rates.

OBJECTIVE

To investigate the plausibility of a contribution of colorectal endoscopy use to the decrease in CRC risk.

DESIGN

Descriptive analysis of temporal trends.

SETTING

U.S. population from 1978 to 2007.

MAIN OUTCOME MEASUREMENTS

Using incidence data from the Surveillance, Epidemiology and End Results Program, we assessed the subsite-specific cumulative risk of CRC developing until age 79 years.

RESULTS

The cumulative risk of proximal CRC remained relatively stable over the observation period, varying between 2.09% (95% CI, 2.06%-2.11%) and 2.66% (95% CI,2.62%-2.69%) for men and between 1.90% (95% CI, 1.88%-1.93%) and 2.24% (95% CI, 2.21%-2.27%) for women. By contrast, the cumulative risk of distal CRC decreased from 4.68% (95% CI, 4.64%-4.73%) to 3.03% (95% CI, 3.00%-3.06%) for men and from 3.15% (95% CI, 3.11%-3.18%) to 1.93% (95% CI, 1.91%-1.95%) for women, which was largely attributable to the reduced cumulative risk of cancer in the sigmoid colon. The observed pattern was restricted to the population aged 50 to 79 years, whereas the magnitude of the decrease was greater for older age groups and similar across stages.

LIMITATIONS

The study is based on aggregated registry data only; therefore, no inferences about causal effects can be drawn.

CONCLUSIONS

The results show a major reduction of CRC risk, particularly in the sigmoid colon. Increased use of colorectal endoscopy in the population aged 50 years and older along with environmental factors may have contributed to the decreasing risk.

Polymorphic variation in the GC and CASR genes and associations with vitamin D metabolite concentration and metachronous colorectal neoplasia

BACKGROUND

Vitamin D levels and calcium intake have been associated with risk of colorectal neoplasia, and genetic variation in vitamin D pathway genes may affect circulating vitamin D metabolite concentrations and/or risk for colorectal lesions. This study evaluated associations between polymorphic variation in the Gc-globulin (GC) and calcium-sensing receptor (CASR) and odds for metachronous colorectal neoplasia and vitamin D metabolite concentrations.

METHODS

Participants from the Ursodeoxycholic Acid (UDCA) and Wheat Bran Fiber (WBF) trials (n = 1,439) were analyzed using a single-nucleotide polymorphism (SNP) tagging approach, with a subset (n = 404) of UDCA trial participants for whom vitamin D metabolite concentrations were also available. A total of 25 GC and 35 CASR tagSNPs were evaluated using multiple statistical methods.

RESULTS

Principal components analyses did not reveal gene-level associations between GC or CASR and colorectal neoplasia; however, a significant gene-level association between GC and 25(OH)D concentrations (P < 0.01) was observed. At the individual SNP level and following multiple comparisons adjustments, significant associations were observed between seven GC (rs7041, rs222035, rs842999, rs1155563, rs12512631, rs16846876, and rs1746825) polymorphisms and circulating measures of 25(OH)D (adjusted P < 0.01) and CASR SNP rs1042636 and proximal colorectal neoplasia (adjusted P = 0.01).

CONCLUSIONS

These results show a possible association between variation in CASR and odds of colorectal neoplasia as well as the potential role of variation in GC with circulating 25(OH)D concentrations.

IMPACT

Additional research is warranted to determine the mechanism of GC genotype in influencing 25(OH)D concentrations and to further elucidate the role of CASR in colorectal neoplasia.

Molecular mechanisms linking adipokines to obesity-related colon cancer: focus on leptin

Obesity is linked to increased risk of colon cancer, currently the third most common cancer. Consequently rising levels of obesity worldwide are likely to significantly impact on obesity-related colon cancers in the decades to come. Understanding the molecular mechanisms whereby obesity increases colon cancer risk is thus a focus for research to inform strategies to prevent the increasing trend in obesity-related cancers. This review will consider research on deregulation of adipokine signalling, a consequence of altered adipokine hormone secretion from excess adipose tissue, with a focus on leptin, which has been studied extensively as a potential mediator of obesity-related colon cancer. Numerous investigations using colon cell lines in vitro, in vivo studies in rodents and investigations of colon cancer patients illuminate the complexity of the interactions of leptin with colon tissues via leptin receptors expressed by the colon epithelium. Although evidence indicates a role for leptin in proliferation of colon epithelial cells in vitro, this has been contradicted by studies in rodent models. However, recent studies have indicated that leptin may influence inflammatory mediators linked with colon cancer and also promote cell growth dependent on genotype and is implicated in growth promotion of colon cancer cells. Studies in human cancer patients indicate that there may be different tumour sub-types with varying levels of leptin receptor expression, indicating the potential for leptin to induce variable responses in the different tumour types. These studies have provided insights into the complex interplay of adipokines with responsive tissues prone to obesity-related colon cancer. Deregulation of adipokine signalling via adipokine receptors located in the colon appears to be a significant factor in obesity-related colon cancer. Molecular profiling of colon tumours will be a useful tool in future strategies to characterise the influence that adipokines may have on tumour development and subsequent therapeutic intervention. Study of the molecular mechanisms linking obesity with cancer also supports recommendations to maintain a normal body weight to reduce the risk of colon cancer.

Timing and intensity of recreational physical activity and the risk of subsite-specific colorectal cancer

PURPOSE

Although there is convincing evidence that physical activity reduces colon cancer risk, there are important questions that remain unanswered about the association. These include the timing and intensity of activity required to optimally reduce risk, and whether physical activity has a different effect on cancers at different sites within the colon. We conducted a case-control study to investigate these issues.

METHODS

A case-control study of colorectal cancer was conducted in Western Australia in 2005-2007. Data were collected on various risk factors. The estimated effects of recreational physical activity on the risk of cancers of the distal colon, proximal colon, and rectum were analyzed using multinomial logistic regression. This analysis included 870 cases and 996 controls.

RESULTS

The risk of distal colon cancer was reduced by performing a high level of vigorous-intensity activity between the ages 19 and 34 years (women), 35 and 50 years (men), after the age of 51 years (men and women), and consistently over the adult lifetime (men and women). The risk of rectal cancer was reduced by performing a high level of vigorous activity between the ages 35 and 50 years (men), and consistently over the adult lifetime (men). Proximal colon cancer risk was not associated with physical activity in any of the age periods or over the adult lifetime. Moderate intensity activity did not reduce the risk of colorectal cancer.

CONCLUSION

Physical activity may have a greater effect on the risk of distal colon cancer than proximal colon cancer. Vigorous physical activity is required to reduce colorectal cancer risk.

Higher bone mineral density is associated with a decreased risk of colorectal adenomas

Bone mineral density (BMD) is a biomarker for cumulative exposure to multiple factors including estrogen, calcium, vitamin D and physical activity, which have all been independently associated with colorectal cancer. Furthermore, higher levels of BMD have been inversely associated with colorectal cancer risk, particularly in postmenopausal women. However, no prior studies have examined the potential association between BMD and colorectal adenomas, which are precursor lesions to most colorectal cancers. Therefore, we evaluated the association between BMD, which was measured using a whole body, dual-energy X-ray absorptiometry scan and colorectal adenomas in 167 patients who underwent colonoscopy screening. We found that patients in the highest tertile of total body BMD (>1.294 g/cm(2)) and in the middle tertile (≥1.167 to ≤1.294 g/cm(2)) compared to those with a total body BMD in the lowest tertile (<1.167 g/cm(2)) had a lower risk of colorectal adenomas (highest vs. lowest tertile: OR = 0.29 (0.10-0.84); middle vs. lowest tertile: OR=0.26 (0.08-0.80); p-trend=0.02). Stratification by gender revealed that this association was more pronounced in women (highest (>1.280 g/cm(2)) vs. lowest (<1.130 g/cm(2)) tertile: OR=0.08 (0.01-0.70); middle (≥1.130 to ≤1.280 g/cm(2)) vs. lowest tertile: OR=0.15 (0.04-0.94); p-trend=0.02) even after excluding hormone replacement therapy users (highest (>1.295 g/cm(2)) and middle (≥1.132 to ≤1.295 g/cm(2)) vs. lowest (<1.132 g/cm(2)) tertile: OR=0.17 (0.03-0.97); p-trend=0.04). Our results show, for the first time, that BMD is inversely associated with colorectal adenomas, particularly in women. Although additional larger, prospective studies are needed, our results suggest that BMD may be a biomarker for colorectal cancer precursor lesions.

Leptin up-regulates pro-inflammatory cytokines in discrete cells within mouse colon

Dysregulation of leptin associated with obesity is implicated in obesity-related colon cancer, but mechanisms are elusive. Increased adiposity and elevated plasma leptin are associated with perturbed metabolism in colon and leptin receptors are expressed on colon epithelium. We hypothesise that obesity increases the sensitivity of the colon to cancer by disrupting leptin-regulated gene targets within colon tissues. PCR arrays were used to firstly identify leptin responsive genes and secondly to identify responses to leptin challenge in wild-type mice, or those lacking leptin (ob/ob). Leptin-regulated genes were localised in the colon using in situ hybridisation. IL6, IL1β and CXCL1 were up-regulated by leptin and localised to discrete cells in gut epithelium, lamina propria, muscularis and at the peritoneal serosal surface. Leptin regulates pro-inflammatory genes such as IL6, IL1β and CXCL1, and might increase the risk of colon cancer among obese individuals.

Racial disparities in risk of second primary cancers in endometrial cancer patients: Analysis of SEER Data

INTRODUCTION: Endometrial cancer (EC) is the most common gynecologic cancer in the United States. Racial disparities in the incidence and mortality of this cancer are apparent; black women are less likely to develop this malignancy, and yet are more likely to die when diagnosed. Racial differences of second primary cancer (SPC) have not been examined and are the goal of this study. METHODS: Using the National Cancer Institute's Surveillance, Epidemiology, and End Results database, SPC risk in white and black EC cases was compared to the general population and to women with other primary cancers. Standardized incidence ratios (SIRs) of SPC (overall and by tumor site) with 95% confidence intervals were calculated. Poisson regression was used to estimate the race-specific risk of SPC in EC cases treated with radiotherapy vs. non-irradiated cases. RESULTS: The analysis included 11,047 EC cases diagnosed between 1973 and 2007 that developed a SPC. Overall risk of SPC in white EC cases was significantly lower than the general population (SIR=0.85, 95% CI: 0.84, 0.87), but significantly higher in black EC cases (SIR=1.19, 95% CI: 1.08, 1.31). White EC cases treated with radiotherapy were more likely to develop SPC compared to non-irradiated cases (IRR=1.18, 95% CI: 1.14, 1.23). CONCLUSIONS: This is the first analysis of race-specific SPC risk in EC cases and it suggests differences between white and black cases. Although exploratory, these data provide important clues about the etiology of SPC in patients with EC. This analysis also highlights the need for careful monitoring following diagnosis and treatment of EC.

Colorectal cancer: what should patients and families be told to lower the risk of colorectal cancer?

Colorectal cancer (CRC) is the second most common cause of cancer-related death in the United States. CRC, however, is potentially preventable, and several strategies may be employed to decrease the incidence of and mortality from CRC. Understanding of individual risk and adherence to screening and surveillance recommendations undoubtedly will reduce CRC-associated deaths. Several natural and synthetic chemopreventive agents may prove effective for both primary and secondary CRC chemoprevention. Finally, dietary modifications (ie, increased dietary fiber, fruits and vegetables, and decreased red meat) and other lifestyle changes (i.e., increased physical activity, weight maintenance, avoidance of smoking, and moderation of alcohol intake) also may lower the risk of developing CRC.

State of the epidemiological evidence on physical activity and cancer prevention

BACKGROUND

Physical activity is a modifiable lifestyle risk factor that has the potential to reduce the risk of most major cancer sites.

METHODS

We examined the strength, consistency, dose-response and biological plausibility of an association between physical activity and risk of colon, breast, endometrium, lung, prostate, ovarian, gastric, rectal, pancreatic, bladder, testicular, kidney and haematological cancers. We also estimated the population-attributable risk (PAR) for physical inactivity and cancer in 15 European countries.

RESULTS

There is convincing or probable evidence for a beneficial effect of physical activity on the risk of colon, breast and endometrial cancers. The evidence is weaker for ovarian, lung and prostate cancers and generally either null or insufficient for all remaining cancers. Several hypothesised biological mechanisms include a likely effect of physical activity on insulin resistance, body composition, sex steroid hormones and a possible effect on vitamin D, adipokines, inflammation and immune function. Somewhere between 165,000 and 330,000 cases of the six major cancers (breast, colon, lung, prostate, endometrium and ovarian) could have been prevented in 2008 in Europe alone if the population had maintained sufficient levels of physical activity.

CONCLUSION

There is strong and consistent evidence that physical activity reduces the risk of several of the major cancer sites, and that between 9% and 19% of cancer cases could be attributed to lack of sufficient physical activity in Europe. Public health recommendations for physical activity and cancer prevention generally suggest 30-60 min of moderate or vigorous-intensity activity done at least 5d per week.

Lifestyle changes and reduction of colon cancer incidence in Europe: A scenario study of physical activity promotion and weight reduction

BACKGROUND

Across Europe, there are over 300,000 new cases of colorectal cancer annually. Major risk factors include excess body weight (usually expressed by a high body mass index, BMI) and physical inactivity (PA). In this study we modelled the potential long-term effects on colon cancer incidence of changes in prevalence of excess body weight and physical inactivity in seven European countries across Europe with adequate data.

METHODS

We addressed the impact of interventions aimed at preventing weight gain and increasing physical activity on colon cancer incidence using the Prevent model as refined in the FP-6 Eurocadet project. Relative risk (RR) estimates were derived from meta-analyses; sex- and country-specific prevalences of BMI and PA were determined from survey data. Models were made for Czech Republic, Denmark, France, Latvia, the Netherlands, Spain and the United Kingdom.

RESULTS

In a hypothetical scenario in which a whole population had obtained an ideal weight distribution in the year 2009, up to 11 new cases per 100,000 person-years would be avoided by 2040. The population attributable fractions (PAF) for excess weight were much higher for males (between 13.5% and 18.2%) than for females (2.3-4.6%). In contrast, using the optimum scenario where everybody in Europe would adhere to the recommended guideline of at least 30 min of moderate PA 5d per week, the PAFs for PA in various countries were substantially greater in women (4.4-21.2%) than in men (3.2-11.6%). Sensitivity analyses were performed assuming underreporting of BMI by using self-reports (difference of 5 and 0.8 percent-points in males and females, respectively), using different risk estimates (between 5.8 and 11.5 percent-points difference for BMI for men and women, respectively, and up to 11.6 percent-points difference for PA for women).

INTERPRETATION

Changes in lifestyle can indeed result in large health benefits, including for colon cancer. Two interesting patterns emerged: for colon cancer, achieving optimum BMI levels in the population appears to offer the greatest health benefits in population attributable fractions in males, while increased physical activity might offer the greatest fraction of avoidable cancers in females. These observations suggest a sex-specific strategy to colon cancer prevention.

Walking pace, leisure time physical activity, and resting heart rate in relation to disease-specific mortality in London: 40 years follow-up of the original Whitehall study. An update of our work with professor Jerry N. Morris (1910-2009)

PURPOSE

To examine the association of leisure time physical activity, walking pace and resting heart rate with disease-specific mortality in a prospective cohort study by reporting updated analyses of an earlier report we produced with the British epidemiologist, Jerry N. Morris (1910-2009).

METHODS

In the original Whitehall study, 19,019 male, nonindustrial, London-based government employees, aged from 40 to 69 years in 1967 and 1970, participated in a medical examination during which data on leisure time physical activity (N = 6715), self-rated walking pace (N = 6729), and resting heart rate (N = 1183) were collected. Cox proportional hazards analyses were used to estimate hazard ratios for the relation between these exposures and disease-specific mortality.

RESULTS

In models adjusted for a range of covariates including socioeconomic status, smoking, and obesity, high resting heart rate was associated with a modestly elevated rate of mortality from all causes (hazard ratio; 95% confidence interval: tertile 3 vs. tertile 1: 1.17; 0.99, 1.37 p[trend]: 0.07) and respiratory disease (1.69; 1.04, 2.76 p[trend]: 0.03). Of the two markers of physical activity, walking pace was inversely related to mortality ascribed to all causes (slow vs. high walking pace 1.71; 1.53, 1.91 p[trend]: <0.001]), coronary heart disease (2.03; 1.68, 2.47 p[trend]: <0.001), and total cancers (1.25; 0.98, 1.59 p[trend]: 0.04). The corresponding associations for leisure time activity were typically weaker. For other mortality endpoints-respiratory disease (walking pace: 1.96; 1.48, 2.60 p[trend]: <0.001]), hematopoietic cancer (walking pace: 1.36; 0.52, 3.51 p[trend]: 0.03), stomach cancer (inactive versus active leisure time: 1.53; 0.88, 2.64 p[trend]: 0.04), and rectal cancer (walking pace: 4.85; 1.70, 13.8 p[trend]: 0.007)-individual activity indices revealed effects, but not both.

CONCLUSIONS

Higher levels of physical activity indexed by the various markers herein appeared to confer protection against a range of mortality outcomes.

Diet, physical activity, and body size associations with rectal tumor mutations and epigenetic changes

Diet and lifestyle factors have been inconsistently associated with rectal tumors. It is possible that evaluation of specific tumor markers with these factors may help clarify these associations. In this study, we examine energy contributing nutrients, dietary fiber, BMI (kg/m2), and long-term physical activity with TP53 mutations, KRAS2 mutations, and CpG Island Methylator Phenotype (CIMP) in 750 population-based cases of rectal cancer compared to healthy controls. We observed that high levels of physical activity reduced the risk of having TP53 and KRAS2 rectal tumor mutations. Dairy products rich in fat were associated with an increased risk of CIMP+ tumors (OR 1.88 95% CI 0.92, 3.84), while low-fat dairy products reduced risk of CIMP+ tumors (OR 0.56 95% CI 0.29, 1.09). Omega-3 fatty acids were associated with a twofold increased risk of a CIMP+ tumor. High levels of vegetable intake reduced risk of both TP53 mutations (OR 0.73 95% CI 0.54, 1.00; p trend 0.02) and KRAS2 mutations (OR 0.60 95% CI 0.40, 0.89; p trend <0.01). High intake of whole grains reduced the likelihood of a TP53 mutation (OR 0.74 95% CI 0.56, 0.99), while high intake of refined grains increased the likelihood of a TP53 mutation (OR 1.41 95% CI 1.02, 1.96). Dietary fiber also was associated with reduced risk of TP53 and KRAS2 rectal tumor mutations. Overall, a prudent dietary pattern significantly reduced the likelihood of a KRAS2 tumor mutation (OR 0.68 95% CI 0.47, 0.98; p linear trend 0.03). These data suggest that diet and lifestyle factors are associated with specific types of rectal tumor mutations and epigenetic changes. Findings need confirmation in other studies.

Colorectal cancer incidence trends in the United States and United kingdom: evidence of right- to left-sided biological gradients with implications for screening

Several lines of evidence support the premise that screening colonoscopy reduces colorectal cancer (CRC) incidence, but there may be differential benefits for right- and left-sided tumors. To better understand the biological basis of this differential effect, we derived biomathematical models of CRC incidence trends in U.S. and U.K. populations, representing relatively high- and low-prevalence screening, respectively. Using the Surveillance Epidemiology and End Results (SEER) and the Office for National Statistics (ONS) registries (both 1973-2006), we derived stochastic multistage clonal expansion (MSCE) models for right-sided (proximal colon) and left-sided (distal colon and rectal) tumors. The MSCE concept is based on the initiation-promotion-progression paradigm of carcinogenesis and provides a quantitative description of natural tumor development from the initiation of an adenoma (via biallelic tumor suppressor gene inactivation) to the clinical detection of CRC. From 1,228,036 (SEER: 340,582; ONS: 887,454) cases, parameter estimates for models adjusted for calendar-year and birth-cohort effects showed that adenoma initiation rates were higher for right-sided tumors, whereas, paradoxically, adenoma growth rates were higher for left-sided tumors. The net effect was a higher cancer risk in the right colon only after age 70 years. Consistent with this finding, simulations of adenoma development predicted that the relative prevalence for right- versus left-sided tumors increases with increasing age, a differential effect most striking in women. Using a realistic biomathematical description of CRC development for two nationally representative registries, we show age- and sex-dependent biological gradients for right- and left-sided colorectal tumors. These findings argue for an age-, sex-, and site-directed approach to CRC screening.

Annual report to the nation on the status of cancer, 1975-2006, featuring colorectal cancer trends and impact of interventions (risk factors, screening, and treatment) to reduce future rates

BACKGROUND

The American Cancer Society, the Centers for Disease Control and Prevention (CDC), the National Cancer Institute (NCI), and the North American Association of Central Cancer Registries (NAACCR) collaborate annually to provide updated information regarding cancer occurrence and trends in the United States. This year's report includes trends in colorectal cancer (CRC) incidence and death rates and highlights the use of microsimulation modeling as a tool for interpreting past trends and projecting future trends to assist in cancer control planning and policy decisions.

METHODS

Information regarding invasive cancers was obtained from the NCI, CDC, and NAACCR; and information on deaths was obtained from the CDC's National Center for Health Statistics. Annual percentage changes in the age-standardized incidence and death rates (based on the year 2000 US population standard) for all cancers combined and for the top 15 cancers were estimated by joinpoint analysis of long-term trends (1975-2006) and for short-term fixed-interval trends (1997-2006). All statistical tests were 2-sided.

RESULTS

Both incidence and death rates from all cancers combined significantly declined (P < .05) in the most recent time period for men and women overall and for most racial and ethnic populations. These decreases were driven largely by declines in both incidence and death rates for the 3 most common cancers in men (ie, lung and prostate cancers and CRC) and for 2 of the 3 leading cancers in women (ie, breast cancer and CRC). The long-term trends for lung cancer mortality in women had smaller and smaller increases until 2003, when there was a change to a nonsignificant decline. Microsimulation modeling demonstrates that declines in CRC death rates are consistent with a relatively large contribution from screening and with a smaller but demonstrable impact of risk factor reductions and improved treatments. These declines are projected to continue if risk factor modification, screening, and treatment remain at current rates, but they could be accelerated further with favorable trends in risk factors and higher utilization of screening and optimal treatment.

CONCLUSIONS

Although the decrease in overall cancer incidence and death rates is encouraging, rising incidence and mortality for some cancers are of concern.

Cancer survivorship, mor(t)ality and lifestyle discourses on cancer prevention

Despite ongoing controversies regarding the impact of lifestyle factors such as body weight, diet and exercise on health, this framework has become increasingly prominent in understandings of cancer aetiology. To date, little consideration has been given to the impacts of such discourses on people with a history of cancer. Drawing on an ethnographic study of cancer survivors, I explore the constitutive dimensions of these discourses and the ways that they shape the subjectivities of women and men with a history of the disease. Overall, the study participants evidenced a complex and ambivalent engagement with such discourses. While they were generally unwilling to accept that their lifestyle had an impact on the development of their cancer, to varying degrees they endorsed the idea that weight, diet and exercise affected cancer progression. However, this acceptance was generally borne of an active desire to gain control over the uncertainty of living with the disease and was mediated by other aspects of the experience of surviving cancer.

Annual report to the nation on the status of cancer, 1975-2006, featuring colorectal cancer trends and impact of interventions (risk factors, screening, and treatment) to reduce future rates

BACKGROUND

The American Cancer Society, the Centers for Disease Control and Prevention (CDC), the National Cancer Institute (NCI), and the North American Association of Central Cancer Registries (NAACCR) collaborate annually to provide updated information regarding cancer occurrence and trends in the United States. This year's report includes trends in colorectal cancer (CRC) incidence and death rates and highlights the use of microsimulation modeling as a tool for interpreting past trends and projecting future trends to assist in cancer control planning and policy decisions.

METHODS

Information regarding invasive cancers was obtained from the NCI, CDC, and NAACCR; and information on deaths was obtained from the CDC's National Center for Health Statistics. Annual percentage changes in the age-standardized incidence and death rates (based on the year 2000 US population standard) for all cancers combined and for the top 15 cancers were estimated by joinpoint analysis of long-term trends (1975-2006) and for short-term fixed-interval trends (1997-2006). All statistical tests were 2-sided.

RESULTS

Both incidence and death rates from all cancers combined significantly declined (P < .05) in the most recent time period for men and women overall and for most racial and ethnic populations. These decreases were driven largely by declines in both incidence and death rates for the 3 most common cancers in men (ie, lung and prostate cancers and CRC) and for 2 of the 3 leading cancers in women (ie, breast cancer and CRC). The long-term trends for lung cancer mortality in women had smaller and smaller increases until 2003, when there was a change to a nonsignificant decline. Microsimulation modeling demonstrates that declines in CRC death rates are consistent with a relatively large contribution from screening and with a smaller but demonstrable impact of risk factor reductions and improved treatments. These declines are projected to continue if risk factor modification, screening, and treatment remain at current rates, but they could be accelerated further with favorable trends in risk factors and higher utilization of screening and optimal treatment.

CONCLUSIONS

Although the decrease in overall cancer incidence and death rates is encouraging, rising incidence and mortality for some cancers are of concern.

Physical activity and gastrointestinal cancer survivorship

Research examining physical activity in gastrointestinal cancer survivors is in its early stages and has focused primarily on colorectal cancer. Moreover, the majority of the research to date has been observational in nature, with very little interventional research. Though limited, the results of this research have been promising in nature, showing positive associations between physical activity and quality of life as well as disease outcomes, including improved disease-free and overall survival. The potential benefits of physical activity for gastrointestinal cancer survivors warrant further research on the underlying mechanisms of the relationship between physical activity and colorectal cancer disease outcomes, to determine if these associations extend to other gastrointestinal cancers, and to determine appropriate physical activity interventions to realize any potential supportive care benefits in various gastrointestinal cancer survivor groups.

Public health benefits of strategies to reduce greenhouse-gas emissions: urban land transport

We used Comparative Risk Assessment methods to estimate the health effects of alternative urban land transport scenarios for two settings-London, UK, and Delhi, India. For each setting, we compared a business-as-usual 2030 projection (without policies for reduction of greenhouse gases) with alternative scenarios-lower-carbon-emission motor vehicles, increased active travel, and a combination of the two. We developed separate models that linked transport scenarios with physical activity, air pollution, and risk of road traffic injury. In both cities, we noted that reduction in carbon dioxide emissions through an increase in active travel and less use of motor vehicles had larger health benefits per million population (7332 disability-adjusted life-years [DALYs] in London, and 12 516 in Delhi in 1 year) than from the increased use of lower-emission motor vehicles (160 DALYs in London, and 1696 in Delhi). However, combination of active travel and lower-emission motor vehicles would give the largest benefits (7439 DALYs in London, 12 995 in Delhi), notably from a reduction in the number of years of life lost from ischaemic heart disease (10-19% in London, 11-25% in Delhi). Although uncertainties remain, climate change mitigation in transport should benefit public health substantially. Policies to increase the acceptability, appeal, and safety of active urban travel, and discourage travel in private motor vehicles would provide larger health benefits than would policies that focus solely on lower-emission motor vehicles.

Effect of aerobic exercise on tumor physiology in an animal model of human breast cancer

Recent epidemiologic studies report that regular exercise may be associated with substantial reductions in cancer-specific and all-cause mortality following a breast cancer diagnosis. The mechanisms underlying this relationship have not been identified. We investigated the effects of long-term voluntary wheel running on growth and progression using an animal model of human breast cancer. We also examined effects on the central features of tumor physiology, including markers of tumor blood perfusion/vascularization, hypoxia, angiogenesis, and metabolism. Athymic female mice fed a high-fat diet were orthotopically (direct into the mammary fat pad) implanted with human breast cancer cells (MDA-MB-231 at 1 x 10(6)) into the right dorsal mammary fat pad and randomly assigned (1:1) to voluntary wheel running (n = 25) or a nonintervention (sedentary) control group (n = 25). Tumor volume was measured every three days using digital calipers. All experimental animals were killed when tumor volume reached > or = 1,500 mm(3). Kaplan-Meier (KM) analysis indicated that tumor growth (survival) was comparable between the experimental groups (exercise 44 days vs. control 48 days; KM proportional hazard ratio = 1.41, 95% confidence interval, 0.77-2.58, P = 0.14). However, tumors from exercising animals had significantly improved blood perfusion/vascularization relative to the sedentary control group (P < 0.05). Histological analyses indicated that intratumoral hypoxia levels (as assessed by hypoxia-inducible factor 1) were significantly higher in the exercise group relative to sedentary control (P < 0.05). Aerobic exercise can significantly increase intratumoral vascularization, leading to "normalization" of the tissue microenvironment in human breast tumors. Such findings may have important implications for inhibiting tumor metastasis and improving the efficacy of conventional cancer therapies.