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

Instrumented Assessment of Physical Activity Is Associated With Muscle Function but Not With Muscle Mass in a General Population

OBJECTIVES

Self-reported physical activity has shown to affect muscle-related parameters. As self-report is likely biased, this study aimed to assess the association between instrumented assessment of physical activity (I-PA) and muscle-related parameters in a general population.

METHOD

Included were 156 young-to-middle-aged and 80 older community-dwelling adults. Seven days of trunk accelerometry (DynaPort MoveMonitor, McRoberts B.V.) quantified daily physical activity (i.e., active/inactive duration, number and mean duration of active/inactive periods, and number of steps per day). Muscle-related parameters included muscle mass, handgrip strength, and gait speed.

RESULTS

I-PA was associated with handgrip strength in young-to-middle-aged adults and with gait speed in older adults. I-PA was not associated with muscle mass in either age group.

DISCUSSION

The association between I-PA and muscle-related parameters was age dependent. The lack of an association between I-PA and muscle mass indicates the relevance of muscle function rather than muscle mass.

The association of lifetime physical inactivity with bladder and renal cancer risk: A hospital-based case-control analysis

OBJECTIVES

Recreational physical inactivity has been gaining recognition as an independent epidemiological exposure of interest in relation to cancer endpoints due to evidence suggesting that it may associate with cancer independent of obesity. In the current analyses, we examined the associations of lifetime recreational physical inactivity with renal and bladder cancer risk.

METHODS

In this hospital-based case-control study, we identified N=160 renal cancer patients, N=208 bladder cancer patients, and N=766 age frequency-matched controls without cancer. Participants self-reporting never participating in any regular/weekly recreational physical activity throughout their lifetime were classified as physically inactive. Utilizing unconditional multivariable logistic regression analyses, we estimated odds ratios and 95% confidence intervals to represent the associations between lifetime physical inactivity and renal and bladder cancer risk.

RESULTS

In multivariable logistic regression models, we observed significant positive associations between lifetime recreational physical inactivity and renal cancer and bladder cancer risk: odds ratio=1.77 (95% CI: 1.10-2.85) and odds ratio=1.73 (95% CI: 1.13-2.63), respectively. Similar associations also persisted among individuals who were not obese for both renal and bladder cancer: odds ratio=1.75 (95% CI: 1.03-2.98) and odds ratio=1.70 (95% CI: 1.08-2.69), respectively.

CONCLUSIONS

In this case-control study, we observed evidence of a positive association between renal and bladder cancer with lifetime recreational physical inactivity. These data add to the growing body of evidence suggesting that physical inactivity may be an important independent risk factor for cancer. However, additional studies using a larger sample and prospectively collected data are needed to substantiate the current findings.

Cancer incidence attributable to inadequate physical activity in Alberta in 2012

BACKGROUND

Physical inactivity has been consistently associated with increased risk of colorectal, endometrial, breast (in postmenopausal women), prostate, lung and ovarian cancers. The objective of the current analysis was to estimate the proportion and absolute number of site-specific cancer cases attributable to inadequate physical activity in Alberta in 2012.

METHODS

We used population attributable risks to estimate the proportion of each site-specific cancer attributable to inactivity. Relative risk estimates were obtained from the epidemiological literature, and prevalence estimates were calculated with the use of data from the Canadian Community Health Survey cycle 2.1 (2003). Respondents who acquired 1.5-2.9 kcal/kg per day and less than 1.5 kcal/kg per day of physical activity were classified as moderately active and inactive, respectively, and both levels were considered inadequate for mitigating cancer risks. We obtained age-, sex- and site-specific cancer incidence data from the Alberta Cancer Registry for 2012.

RESULTS

About 59%-75% of men and 69%-78% of women did not engage in adequate physical activity. Overall, 13.8% of cancers across all associated cancers were estimated to be attributable to inadequate physical activity, representing 7.2% of all cancers diagnosed in Alberta in 2012. Suboptimal levels of physical activity had a greater impact among women: the proportion of all associated cancers attributable to inadequate physical activity was 18.3% for women and 9.9% for men.

INTERPRETATION

A substantial proportion of cancer cases diagnosed in Alberta were estimated to be attributable to inadequate physical activity. With the high prevalence of physical inactivity among adults in the province, developing strategies to increase physical activity levels could have a notable impact on reducing future cancer burden in Alberta.

Exercise-induced biochemical changes and their potential influence on cancer: a scientific review

AIM

To review and discuss the available international literature regarding the indirect and direct biochemical mechanisms that occur after exercise, which could positively, or negatively, influence oncogenic pathways.

METHODS

The PubMed, MEDLINE, Embase and Cochrane libraries were searched for papers up to July 2016 addressing biochemical changes after exercise with a particular reference to cancer. The three authors independently assessed their appropriateness for inclusion in this review based on their scientific quality and relevance.

RESULTS

168 papers were selected and categorised into indirect and direct biochemical pathways. The indirect effects included changes in vitamin D, weight reduction, sunlight exposure and improved mood. The direct effects included insulin-like growth factor, epigenetic effects on gene expression and DNA repair, vasoactive intestinal peptide, oxidative stress and antioxidant pathways, heat shock proteins, testosterone, irisin, immunity, chronic inflammation and prostaglandins, energy metabolism and insulin resistance.

SUMMARY

Exercise is one of several lifestyle factors known to lower the risk of developing cancer and is associated with lower relapse rates and better survival. This review highlights the numerous biochemical processes, which explain these potential anticancer benefits.

Serum levels of HMGB1 have a diagnostic role in metastatic renal cell cancer

RCC constitutes approximately 90% of all renal malignancies and 2-3% of all malignant tumours in adults. In spite of the improvement in radiologic methods, nearly 30% of the early metastatic RCC patients are incidentally diagnosed. HMGB1 is an extracellular signalling molecule that plays a role both in inflammation and carcinogenesis. Patients who were followed in Medical Oncology Departments of Denizli Government Hospital and Antalya Education and Research Hospital with a histopathological diagnosis of RCC between years 2010-2012 were enrolled in this study. HMGB1 levels were also assessed in a manually performed quantitative sandwich-enzyme-linked immunosorbent assay (ELISA) assay kit. In our study, we showed that the serum level of HMGB1, whether 149.9 pg/ml or not is important in differential diagnosis between patient and control group.

Increasing trends in kidney cancer over the last 2 decades in Saudi Arabia

Objectives:

To examine the trends of kidney cancer over the last 2 decades in a subset of a Saudi Arabian population.

Methods:

We conducted a retrospective study in a tertiary care center including all adult patients with primary kidney cancer who presented and were managed between 1990 and 2010. The time period was split into 4 quartiles, and variables tested and compared using chi-square, T-test, and Kaplan-Meier curves for survival.

Results:

The total was 215 patients with a mean age of 57.8 years. There was an increase in the number of kidney cancer cases over the last 2 decades. There was no significant difference in the mode of presentation or stage distribution between quartiles. A significant change was observed in the management towards minimally invasive and nephron-sparing surgeries (p<0.001). There was no change in recurrence-free and disease-specific survival over the last 20 years.

Conclusions:

There have been an increasing number of kidney cancer patients over the last 2 decades with no observed migration towards more incidental and low stage tumors as compared with developed countries.

Physical Activity and Gastric Cancer Risk: A Systematic Review and Meta-Analysis

OBJECTIVE

Physical activity represents a well-established way to prolong the life span; yet, it remains an unfulfilled goal for a great part of the population. In parallel, the burden of gastric cancer is considerable throughout the globe. In that context, the present meta-analysis aims to shed light on the association between physical activity and gastric cancer risk.

DATA SOURCES

Eligible observational studies were sought in PubMed up to June 01, 2015. In addition, a snowball procedure was conducted and contact with authors was implemented. Separate analyses were performed by type of physical activity (total; occupational; recreational), study design, published/provided data, anatomical site, and study location, along with stratification by gender.

MAIN RESULTS

Ten cohort studies (7551 incident cases in a total cohort size of 1 541 208 subjects) and 12 case-control studies (5803 cases and 73 629 controls) were eligible. "Any" type of physical activity was associated with lower risk of gastric cancer [pooled relative risk (RR) = 0.81; 95% CI: 0.73 to 0.89], which was reproducible in men (pooled RR = 0.87; 95% CI: 0.77-0.99). The protective effect was significant in the subgroup analyses of published data, noncardia cancer (pooled RR = 0.62; 95% CI: 0.52-0.75), and studies stemming from Asia (pooled RR = 0.82; 95% CI: 0.74-0.90).

CONCLUSIONS

This meta-analysis suggests a protective effect of physical activity regarding gastric cancer risk, especially in Asian populations.

Exercise and Prostate Cancer: Evidence and Proposed Mechanisms for Disease Modification

Exercise has many potential benefits in relation to cancer. Apart from primary prevention, these include improvement of nonspecific cancer-related symptoms, amelioration of symptoms and cardiovascular risk factors related to cancer treatment, and improvements in various quality-of-life-related factors. Increasing evidence also points toward improved cancer-free and overall survival in cancer patients who undertake regular exercise, findings which should encourage further research in this area. Obesity is known to be associated with a proinflammatory, prothrombotic humoral milieu, which may promote aggressiveness in prostate cancer through interactions with NK-cell-mediated killing of circulating tumor cells, through platelet-circulating tumor cell interactions, and through alterations in adipokine and myokine profile among others. Physical activity reduces levels of systemic inflammatory mediators and so exercise may represent an accessible and cost-effective means of ameliorating the proinflammatory effects of obesity in cancer patients. This review outlines the evidence for the benefits of exercise in these patients, focusing on prostate cancer, and delineates current theories of the underlying biological mechanisms. Cancer Epidemiol Biomarkers Prev; 25(9); 1281-8. ©2016 AACR.

Association of Leisure-Time Physical Activity With Risk of 26 Types of Cancer in 1.44 Million Adults

IMPORTANCE

Leisure-time physical activity has been associated with lower risk of heart-disease and all-cause mortality, but its association with risk of cancer is not well understood.

OBJECTIVE

To determine the association of leisure-time physical activity with incidence of common types of cancer and whether associations vary by body size and/or smoking.

DESIGN, SETTING, AND PARTICIPANTS

We pooled data from 12 prospective US and European cohorts with self-reported physical activity (baseline, 1987-2004). We used multivariable Cox regression to estimate hazard ratios (HRs) and 95% confidence intervals for associations of leisure-time physical activity with incidence of 26 types of cancer. Leisure-time physical activity levels were modeled as cohort-specific percentiles on a continuous basis and cohort-specific results were synthesized by random-effects meta-analysis. Hazard ratios for high vs low levels of activity are based on a comparison of risk at the 90th vs 10th percentiles of activity. The data analysis was performed from January 1, 2014, to June 1, 2015.

EXPOSURES

Leisure-time physical activity of a moderate to vigorous intensity.

MAIN OUTCOMES AND MEASURES

Incident cancer during follow-up.

RESULTS

A total of 1.44 million participants (median [range] age, 59 [19-98] years; 57% female) and 186 932 cancers were included. High vs low levels of leisure-time physical activity were associated with lower risks of 13 cancers: esophageal adenocarcinoma (HR, 0.58; 95% CI, 0.37-0.89), liver (HR, 0.73; 95% CI, 0.55-0.98), lung (HR, 0.74; 95% CI, 0.71-0.77), kidney (HR, 0.77; 95% CI, 0.70-0.85), gastric cardia (HR, 0.78; 95% CI, 0.64-0.95), endometrial (HR, 0.79; 95% CI, 0.68-0.92), myeloid leukemia (HR, 0.80; 95% CI, 0.70-0.92), myeloma (HR, 0.83; 95% CI, 0.72-0.95), colon (HR, 0.84; 95% CI, 0.77-0.91), head and neck (HR, 0.85; 95% CI, 0.78-0.93), rectal (HR, 0.87; 95% CI, 0.80-0.95), bladder (HR, 0.87; 95% CI, 0.82-0.92), and breast (HR, 0.90; 95% CI, 0.87-0.93). Body mass index adjustment modestly attenuated associations for several cancers, but 10 of 13 inverse associations remained statistically significant after this adjustment. Leisure-time physical activity was associated with higher risks of malignant melanoma (HR, 1.27; 95% CI, 1.16-1.40) and prostate cancer (HR, 1.05; 95% CI, 1.03-1.08). Associations were generally similar between overweight/obese and normal-weight individuals. Smoking status modified the association for lung cancer but not other smoking-related cancers.

CONCLUSIONS AND RELEVANCE

Leisure-time physical activity was associated with lower risks of many cancer types. Health care professionals counseling inactive adults should emphasize that most of these associations were evident regardless of body size or smoking history, supporting broad generalizability of findings.

Association of Leisure-Time Physical Activity With Risk of 26 Types of Cancer in 1.44 Million Adults

IMPORTANCE

Leisure-time physical activity has been associated with lower risk of heart-disease and all-cause mortality, but its association with risk of cancer is not well understood.

OBJECTIVE

To determine the association of leisure-time physical activity with incidence of common types of cancer and whether associations vary by body size and/or smoking.

DESIGN, SETTING, AND PARTICIPANTS

We pooled data from 12 prospective US and European cohorts with self-reported physical activity (baseline, 1987-2004). We used multivariable Cox regression to estimate hazard ratios (HRs) and 95% confidence intervals for associations of leisure-time physical activity with incidence of 26 types of cancer. Leisure-time physical activity levels were modeled as cohort-specific percentiles on a continuous basis and cohort-specific results were synthesized by random-effects meta-analysis. Hazard ratios for high vs low levels of activity are based on a comparison of risk at the 90th vs 10th percentiles of activity. The data analysis was performed from January 1, 2014, to June 1, 2015.

EXPOSURES

Leisure-time physical activity of a moderate to vigorous intensity.

MAIN OUTCOMES AND MEASURES

Incident cancer during follow-up.

RESULTS

A total of 1.44 million participants (median [range] age, 59 [19-98] years; 57% female) and 186 932 cancers were included. High vs low levels of leisure-time physical activity were associated with lower risks of 13 cancers: esophageal adenocarcinoma (HR, 0.58; 95% CI, 0.37-0.89), liver (HR, 0.73; 95% CI, 0.55-0.98), lung (HR, 0.74; 95% CI, 0.71-0.77), kidney (HR, 0.77; 95% CI, 0.70-0.85), gastric cardia (HR, 0.78; 95% CI, 0.64-0.95), endometrial (HR, 0.79; 95% CI, 0.68-0.92), myeloid leukemia (HR, 0.80; 95% CI, 0.70-0.92), myeloma (HR, 0.83; 95% CI, 0.72-0.95), colon (HR, 0.84; 95% CI, 0.77-0.91), head and neck (HR, 0.85; 95% CI, 0.78-0.93), rectal (HR, 0.87; 95% CI, 0.80-0.95), bladder (HR, 0.87; 95% CI, 0.82-0.92), and breast (HR, 0.90; 95% CI, 0.87-0.93). Body mass index adjustment modestly attenuated associations for several cancers, but 10 of 13 inverse associations remained statistically significant after this adjustment. Leisure-time physical activity was associated with higher risks of malignant melanoma (HR, 1.27; 95% CI, 1.16-1.40) and prostate cancer (HR, 1.05; 95% CI, 1.03-1.08). Associations were generally similar between overweight/obese and normal-weight individuals. Smoking status modified the association for lung cancer but not other smoking-related cancers.

CONCLUSIONS AND RELEVANCE

Leisure-time physical activity was associated with lower risks of many cancer types. Health care professionals counseling inactive adults should emphasize that most of these associations were evident regardless of body size or smoking history, supporting broad generalizability of findings.

The Fraction of Cancer Attributable to Ways of Life, Infections, Occupation, and Environmental Agents in Brazil in 2020

Many human cancers develop as a result of exposure to risk factors related to the environment and ways of life. The aim of this study was to estimate attributable fractions of 25 types of cancers resulting from exposure to modifiable risk factors in Brazil. The prevalence of exposure to selected risk factors among adults was obtained from population-based surveys conducted from 2000 to 2008. Risk estimates were based on data drawn from meta-analyses or large, high quality studies. Population-attributable fractions (PAF) for a combination of risk factors, as well as the number of preventable deaths and cancer cases, were calculated for 2020. The known preventable risk factors studied will account for 34% of cancer cases among men and 35% among women in 2020, and for 46% and 39% deaths, respectively. The highest attributable fractions were estimated for tobacco smoking, infections, low consumption of fruits and vegetables, excess weight, reproductive factors, and physical inactivity. This is the first study to systematically estimate the fraction of cancer attributable to potentially modifiable risk factors in Brazil. Strategies for primary prevention of tobacco smoking and control of infection and the promotion of a healthy diet and physical activity should be the main priorities in policies for cancer prevention in the country.

Hypertension and physical exercise: The role of oxidative stress

Oxidative stress is associated with the pathogenesis of hypertension. Decreased bioavailability of nitric oxide (NO) is one of the mechanisms involved in the pathogenesis. It has been suggested that physical exercise could be a potential non-pharmacological strategy in treatment of hypertension because of its beneficial effects on oxidative stress and endothelial function. The aim of this review is to investigate the effect of oxidative stress in relation to hypertension and physical exercise, including the role of NO in the pathogenesis of hypertension. Endothelial dysfunction and decreased NO levels have been found to have the adverse effects in the correlation between oxidative stress and hypertension. Most of the previous studies found that aerobic exercise significantly decreased blood pressure and oxidative stress in hypertensive subjects, but the intense aerobic exercise can also injure endothelial cells. Isometric exercise decreases normally only systolic blood pressure. An alternative exercise, Tai chi significantly decreases blood pressure and oxidative stress in normotensive elderly, but the effect in hypertensive subjects has not yet been studied. Physical exercise and especially aerobic training can be suggested as an effective intervention in the prevention and treatment of hypertension and cardiovascular disease via reduction in oxidative stress.

Lifestyle and cancer risk

The global incidence of cancer is expected to increase substantially over the next decades. This trend is very much driven by a rise in lifestyle-related cancers due to economic and demographic transitions worldwide. Lifestyle factors, such as smoking, alcohol consumption, obesity, diet, and physical inactivity, and also reproductive and hormonal factors are considered as causes of cancer and main targets for primary prevention. While smoking, which may be responsible for around 20% to 30% of all incident cancers, is clearly the strongest lifestyle-related risk factor overall, followed by alcohol consumption and obesity, the importance of specific factors for individual cancer types and subtypes varies greatly. Remarkably, it has been argued that half of all cancers in industrially developed and affluent societies could be avoided by nonsmoking, reducing alcohol consumption, weight control and physical activity, a plant-based diet, and breast-feeding.

European Code against Cancer 4th Edition: Physical activity and cancer

Physical activity is a complex, multidimensional behavior, the precise measurement of which is challenging in free-living individuals. Nonetheless, representative survey data show that 35% of the European adult population is physically inactive. Inadequate levels of physical activity are disconcerting given substantial epidemiologic evidence showing that physical activity is associated with decreased risks of colon, endometrial, and breast cancers. For example, insufficient physical activity levels are thought to cause 9% of breast cancer cases and 10% of colon cancer cases in Europe. By comparison, the evidence for a beneficial effect of physical activity is less consistent for cancers of the lung, pancreas, ovary, prostate, kidney, and stomach. The biologic pathways underlying the association between physical activity and cancer risk are incompletely defined, but potential etiologic pathways include insulin resistance, growth factors, adipocytokines, steroid hormones, and immune function. In recent years, sedentary behavior has emerged as a potential independent determinant of cancer risk. In cancer survivors, physical activity has shown positive effects on body composition, physical fitness, quality of life, anxiety, and self-esteem. Physical activity may also carry benefits regarding cancer survival, but more evidence linking increased physical activity to prolonged cancer survival is needed. Future studies using new technologies - such as accelerometers and e-tools - will contribute to improved assessments of physical activity. Such advancements in physical activity measurement will help clarify the relationship between physical activity and cancer risk and survival. Taking the overall existing evidence into account, the fourth edition of the European Code against Cancer recommends that people be physically active in everyday life and limit the time spent sitting.

Cardiopulmonary exercise testing for risk prediction in major abdominal surgery

Reduced exercise capacity is associated with increased postoperative morbidity. Cardiopulmonary exercise testing variables can be used to risk stratify patients. This information can be used to help guide the choice of surgical procedure and to decide on the most appropriate postoperative care environment. Thus CPET can aid collaborative decision making and improve the process of informed consent. In the future, CPET may be combined with other risk predictors to improve outcome prediction. Furthermore early evidence suggests that CPET can be used to guide prehabilitation training programs, improving fitness and thereby reducing perioperative risk.

Cardiopulmonary exercise testing, prehabilitation, and Enhanced Recovery After Surgery (ERAS)

PURPOSE

This review evaluates the current and future role of cardiopulmonary exercise testing (CPET) in the context of Enhanced Recovery After Surgery (ERAS) programs.

PRINCIPAL FINDINGS

There is substantial literature confirming the relationship between physical fitness and perioperative outcome in general. The few small studies in patients undergoing surgery within an ERAS program describe less fit individuals having a greater incidence of morbidity and mortality. There is evidence of increasing adoption of perioperative CPET, particularly in the UK. Although CPET-derived variables have been used to guide clinical decisions about choice of surgical procedure and level of perioperative care as well as to screen for uncommon comorbidities, the ability of CPET-derived variables to guide therapy and thereby improve outcome remains uncertain. Recent studies have reported a reduction in CPET-defined physical fitness following neoadjuvant therapies (chemo- and radio-therapy) prior to surgery. Preliminary data suggest that this effect may be associated with an adverse effect on clinical outcomes in less fit patients. Early reports suggest that CPET-derived variables can be used to guide the prescription of exercise training interventions and thereby improve physical fitness in patients prior to surgery (i.e., prehabilitation). The impact of such interventions on clinical outcomes remains uncertain.

CONCLUSIONS

Perioperative CPET is finding an increasing spectrum of roles, including risk evaluation, collaborative decision-making, personalized care, monitoring interventions, and guiding prescription of prehabilitation. These indications are potentially of importance to patients having surgery within an ERAS program, but there are currently few publications specific to CPET in the context of ERAS programs.

Cardiopulmonary exercise testing, prehabilitation, and Enhanced Recovery After Surgery (ERAS)

PURPOSE

This review evaluates the current and future role of cardiopulmonary exercise testing (CPET) in the context of Enhanced Recovery After Surgery (ERAS) programs.

PRINCIPAL FINDINGS

There is substantial literature confirming the relationship between physical fitness and perioperative outcome in general. The few small studies in patients undergoing surgery within an ERAS program describe less fit individuals having a greater incidence of morbidity and mortality. There is evidence of increasing adoption of perioperative CPET, particularly in the UK. Although CPET-derived variables have been used to guide clinical decisions about choice of surgical procedure and level of perioperative care as well as to screen for uncommon comorbidities, the ability of CPET-derived variables to guide therapy and thereby improve outcome remains uncertain. Recent studies have reported a reduction in CPET-defined physical fitness following neoadjuvant therapies (chemo- and radio-therapy) prior to surgery. Preliminary data suggest that this effect may be associated with an adverse effect on clinical outcomes in less fit patients. Early reports suggest that CPET-derived variables can be used to guide the prescription of exercise training interventions and thereby improve physical fitness in patients prior to surgery (i.e., prehabilitation). The impact of such interventions on clinical outcomes remains uncertain.

CONCLUSIONS

Perioperative CPET is finding an increasing spectrum of roles, including risk evaluation, collaborative decision-making, personalized care, monitoring interventions, and guiding prescription of prehabilitation. These indications are potentially of importance to patients having surgery within an ERAS program, but there are currently few publications specific to CPET in the context of ERAS programs.

Physical activity and renal cell carcinoma among black and white Americans: a case-control study

Background

Renal cell carcinoma (RCC) has a higher incidence in blacks than in whites. Physical activity may influence the risk of renal cell cancer, but the evidence is inconsistent. No previous study has investigated this relationship in the black population.

Methods

We examined the association between self-reported physical activity at different ages and risk of RCC in a population based case-control study of 1217 cases (361 black, 856 white) and 1235 controls (523 black, 712 white) frequency-matched on age, race, and gender. Multivariate-adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using unconditional logistic regression.

Results

Among whites, increased risks of RCC were observed among participants reporting low levels of transportation-related activity in their 20’s (OR _{<1 hr/wk vs >7 hr/wk} (95% CI): 1.42 (1.10, 1.83)) and leisure time activity in their 50’s (OR _{<1 hr/wk vs >7 hr/wk} (95% CI): 1.49 (1.00, 2.20)). We found no association between physical activity and RCC risk among blacks.

Conclusion

Our results suggest that physical activity may be inversely associated with RCC risk in whites, but there was no evidence of such an association in blacks. As this is the first study evaluating the effect of physical activity on RCC risk among blacks, further investigations are needed to clarify the relationship in this population.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-707) contains supplementary material, which is available to authorized users.

Kidney cancer incidence and mortality among American Indians and Alaska Natives in the United States, 1990-2009

OBJECTIVES

We describe rates and trends in kidney cancer incidence and mortality and identify disparities between American Indian/Alaska Native (AI/AN) and White populations.

METHODS

To improve identification of AI/AN race, incidence and mortality data were linked with Indian Health Service (IHS) patient records. Analysis focused on residents of IHS Contract Health Service Delivery Area counties; Hispanics were excluded. We calculated age-adjusted kidney cancer incidence (2001-2009) and death rates (1990-2009) by sex, age, and IHS region.

RESULTS

AI/AN persons have a 1.6 times higher kidney cancer incidence and a 1.9 times higher kidney cancer death rate than Whites. Despite a significant decline in kidney cancer death rates for Whites (annual percentage change [APC] = -0.3; 95% confidence interval [CI] = -0.5, 0.0), death rates for AI/AN persons remained stable (APC = 0.4; 95% CI = -0.7, 1.5). Kidney cancer incidence rates rose more rapidly for AI/AN persons (APC = 3.5; 95% CI = 1.2, 5.8) than for Whites (APC = 2.1; 95% CI = 1.4, 2.8).

CONCLUSIONS

AI/AN individuals have greater risk of developing and dying of kidney cancers. Incidence rates have increased faster in AI/AN populations than in Whites. Death rates have decreased slightly in Whites but remained stable in AI/AN populations. Racial disparities in kidney cancer are widening.

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

Physical activity may decrease gastroesophageal cancer risk through a reduction of oxidative stress and decreased chronic inflammation, yet few epidemiologic studies have been able to report a clear inverse association between physical activity and gastroesophageal cancer. Because no meta-analysis has investigated the relation of physical activity to gastroesophageal cancer, we conducted a comprehensive systematic review and meta-analysis according to the PRISMA guidelines based on 24 studies with a total of 15,745 cases. When we compared high versus low physical activity levels and summarized associations according to anatomic site and tumor histology, risk reductions were evident for esophageal adenocarcinoma [relative risk (RR) = 0.79, 95% confidence interval (CI) = 0.66-0.94], gastric cardia adenocarcinoma (RR = 0.83, 95% CI = 0.69-0.99) and gastric non-cardia adenocarcinoma (RR = 0.72, 95% CI = 0.62-0.84). The risk reduction for esophageal squamous cell carcinoma (RR = 0.94, 95% CI = 0.41-2.16) became statistically significant (RR = 0.66, 95% CI = 0.46-0.96) after excluding an influential study. The test for heterogeneity by gastroesophageal cancer subtype was statistically non-significant (p-difference = 0.71). The RR of total gastroesophageal cancer for high versus low physical activity was 0.82 (95% CI = 0.74-0.90). A dose-response analysis of frequency of physical activity and total gastroesophageal cancer risk revealed that the greatest risk reduction was achieved among those engaging in moderate to vigorous physical activity five times per week (RR = 0.67, 95% CI = 0.58-0.79). Our results provide support for an inverse relation of physical activity, in particular exercise frequency, to gastroesophageal cancer risk.

Dinitrotoluene exposure in the copper mining industry and renal cancer: a case-cohort study

OBJECTIVES

To evaluate the association between dinitrotoluene (DNT) exposure and renal cancer in a case-cohort study.

METHODS

This case-cohort study was conducted among men born between 1920 and 1974 (n=16 441) who were gainfully employed between 1953 and 1990 in one of two copper mines in Mansfeld, Saxony-Anhalt, former German Democratic Republic, and followed up till 31 December 2006. The study included 109 cases with renal cancer identified by record linkage with the Common Cancer Registry of the New Federal States of Germany (GKR) or by a network of pathology institutes. A comparison subcohort of 999 cohort members was selected at random from the total cohort. Duration and intensity of inhalation and dermal exposure to DNT were assessed on the basis of a job exposure matrix. A time-dependent Cox proportional hazards model modified for case-cohort design was used to assess the relationship between cumulative inhalation and dermal DNT exposure and renal cancer.

RESULTS

Elevated risks were found for medium (HR=2.73; 95% CI 1.00 to 7.42) and high (HR=1.81; 95% CI 0.75 to 4.33) dermal exposure to DNT. Relative risks for medium inhalation exposure to DNT were not increased (HR=0.93; 95% CI 0.48 to 1.79) while relative risks for high inhalation exposure to DNT were elevated to 1.36 (95% CI 0.84 to 2.21). We found a statistically significant HR of 2.12 (95% CI 1.03 to 4.37) for combined medium or high inhalation and medium or high dermal exposure to DNT.

CONCLUSIONS

According to our case-cohort study, dermal and inhalation exposure to DNT is associated with increased renal cancer risk.

Physical activity and gastric cancer: so what? An epidemiologist's confession

Epidemiologists, like many scientists, tend to become specialized and focused on a particular disease, even though behavioral risk factors such as physical activity have effects across many diseases. This commentary is a personal reflection by an epidemiologist on the shortcomings of this disease-oriented approach to prevention.

Social disparities, health risk behaviors, and cancer

BACKGROUND

Overall cancer incidence rates decreased in the most recent time period in both men and women, largely due to improvements in surgical therapeutic approaches (tertiary prevention) and screening programs (secondary prevention), but differences in cancer incidence and survival according to socioeconomic status are documented worldwide. Health risk behaviors, defined as habits or practices that increase an individual's likelihood of harmful health outcomes, are thought to mediate such inequalities.

DISCUSSION

Obesity has been related with increased cancer incidence and mortality due to imbalance of leptin and adiponectin which are connected to activation of PI3K, MAPK, and STAT3 pathways and decreasing insulin/insulin-like growth factor (IGF)-1 and mTOR signaling via activation of 5 AMP-activated protein kinase (AMPK), respectively. Physical activity has been associated to prevent cancer by the aforementioned obesity-related mechanisms, but also increasing level of circulating vitamin D, which has been related to lower risk of several cancers, and increasing prostaglandin F2a and reducing prostaglandin E2, which are both related with cancer prevention and promotion, respectively. A large number of different substances may induce themselves a direct cytotoxicity and mutagenic action on cells by smoking, whereas alcohol promote immune suppression, the delay of DNA repair, inhibition of the detoxification of carcinogens, the production of acetaldehyde, and the contribution to abnormal DNA methylation. The combined smoking and alcohol drinking habits have been shown to increase cancer risk by smoke action of increasing the acetaldehyde burden following alcohol consumption and alcohol action of enhancing the activation of various procarcinogens contained in tobacco smoke.

CONCLUSIONS

Interventions at the social level may be done to increase awareness about cancer risks and promote changing in unhealthy behaviors.