Physical activity before and after diagnosis of colorectal cancer: disease risk, clinical outcomes, response pathways and biomarkers

A longitudinal study of physical activity among Malaysian breast cancer survivors

Regular physical activity (PA) after a breast cancer diagnosis is associated with reduced mortality and better quality of life. In this prospective cohort study, we aimed to explore the trends of PA among breast cancer survivors over three years and identify factors associated with low PA. Interviews on 133 breast cancer patients were conducted at baseline, one and three years after the diagnosis of breast cancer at University Malaya Medical Centre in Kuala Lumpur. Physical activity was measured by using the Global Physical Activity Questionnaire. PA was categorised as active (≥ 600 MET-min/week) and inactive (<600 MET-min/week). We used the generalised estimating equation method to examine PA levels and factors affecting PA longitudinally. The survivors' mean age was 56.89 (±10.56) years; half were Chinese (50.4%), and 70.7% were married. At baseline, 48.1% of the patients were active, but the proportion of active patients declined to 39.8% at one year and 35.3% in the third year. The mean total PA decreased significantly from 3503±6838.3 MET-min/week to 1494.0±2679.8 MET-min/week (one year) and 792.5±1364 MET-min/week (three years) (p<0.001). Three years after diagnosis (adjusted odds ratio [AOR]: 1.74, p = 0.021); Malay ethnicity (AOR: 1.86, p = 0.042) and being underweight (AOR: 3.43, p = 0.004) were significantly associated with inactivity. We demonstrated that breast cancer survivors in Malaysia had inadequate PA levels at diagnosis, which decreased over time. Thus, it is vital to communicate about the benefits of PA on cancer outcomes and continue to encourage breast cancer survivors to be physically active throughout the extended survivorship period, especially in the Malay ethnic group and underweight patients.

The modulatory effects of exercise on the inflammatory and apoptotic markers in rats with 1,2-dimethylhydrazine-induced colorectal cancer

This study aimed to investigate the underlying mechanisms in anti-tumorigenesis effects of exercise through evaluation of inflammation and apoptosis. Twenty-four Wistar rats were divided into control, exercise, 1,2-dimethylhydrazine (DMH), and DMH + exercise. After a week, rats in the DMH group were given DMH twice a week for 2 weeks. Animals in the exercise groups performed exercise on a treadmill 5 days/week for 8 weeks. After 8 weeks of training, levels of COX-2, PCNA, Bax, Bcl-2, and procaspase-3/cleaved caspase-3 were assessed. Histological changes, number of aberrant crypt foci (ACF), and serum levels of TNF-α and IL-6 were also analyzed. ACF number was significantly decreased following the exercise program. Protein levels of COX-2 and PCNA and serum levels of IL-6 and TNF-α were significantly elevated in the rats receiving DMH and downregulated after performing the exercise program (P < 0.05). Exercise upregulated apoptosis, which was evident from the increased Bax/Bcl2 ratio, and enhanced the expression levels of activated caspase-3 as compared to the DMH group. The colonic architecture was improved in DMH + exercise. Exercise can effectively attenuate DMH-induced increase of inflammatory markers. Exercise induces apoptosis at the downstream of the inflammatory response. Therefore, exercise may play a role as a moderator of inflammation to exert protective effects against colon cancer.

Short-term pre-operative high-intensity interval training does not improve fitness of colorectal cancer patients

Background

Pre‐operative cardiorespiratory fitness (CRF) in colorectal cancer (CRC) patients has been shown to affect post‐operative outcomes. The aim of this study was to test the feasibility of high‐intensity interval training (HIIT) for improving fitness in pre‐operative CRC patients within the 31‐day cancer waiting‐time targets imposed in the UK.

Methods

Eighteen CRC patients (13 males, mean age: 67 years (range: 52‐77 years) participated in supervised HIIT on cycle ergometers 3 or 4 times each week prior to surgery. Exercise intensity during 5 × 1‐minute HIIT intervals (interspersed with 90‐second recovery) was 100%‐120% maximum wattage achieved at a baseline cardiopulmonary exercise test (CPET). CPET before and after HIIT was used to assess CRF.

Results

Patients completed a mean of eight HIIT sessions (range 6‐14) over 19 days (SD 7). There was no significant increase in VO₂ peak (23.9 ± 7.0 vs 24.2 ± 7.8 mL/kg/min (mean ± SD), P = 0.58) or anaerobic threshold (AT: 14.0 ± 3.4 vs 14.5 ± 4.5 mL/kg/min, P = 0.50) after HIIT. There was a significant reduction in resting systolic blood pressure (152 ± 19 vs 142 ± 19 mm Hg, P = 0.0005) and heart rate at submaximal exercise intensities after HIIT.

Conclusions

Our pragmatic HIIT exercise protocol did not improve the pre‐operative fitness of CRC patients within the 31‐day window available in the UK to meet cancer surgical waiting‐time targets.

A prospective, multicenter pilot study to investigate the feasibility and safety of a 1-year controlled exercise training after adjuvant chemotherapy in colorectal cancer patients

INTRODUCTION

Despite advances in adjuvant chemotherapy, 20-30% of patients in stages II-III colorectal cancer will eventually relapse. Observational studies showed a reduction in relapse rate, colon cancer-specific mortality, and overall mortality by physical activity. Results from prospective randomized interventional studies to confirm these observational data are lacking. The aims of this prospective single-arm multicenter pilot study are to evaluate feasibility and safety of exercise training after adjuvant chemotherapy in colorectal cancer patients.

PATIENTS AND METHODS

The training was performed three times per week for 1 year and was increased gradually in three phases until reaching 18 metabolic equivalent task hours per week.

RESULTS

Overall, 30 patients were included. The planned training intensity could be achieved in all three phases. Patients experienced a performance increase of median 35.5 watt, a weight-loss of a median of 3.0 kg, and a reduction in body fat content of median 1.0% during this exercise training. The analysis showed early study termination due to non-compliance in 10/30 patients (33.3%), disease progression in 4 patients (13.3%), and serious adverse events in 2 patients (6.7%). About half of patients (46.7%) completed the pilot study as planned. Biomarker analysis from 20 patients showed a non-significant reduction in insulin-like growth factor 1 (IGF-1), insulin-like growth factor 2 (IGF-2) and insulin-like growth factor binding protein 3 (IGF-BP3) levels, significant increases in adiponectin and leptin levels, and a non-significant increase in C-peptide levels.

CONCLUSION

Exercise training is feasible in patients with colorectal cancer after completion of adjuvant chemotherapy. The main problem encountered during the study was compliance. To improve compliance of exercise training, several measures were adapted for the upcoming prospective randomized ABCSG C08 Exercise II study.

Environments Associated with Moderate-to-Vigorous Physical Activity and Sedentary Behavior of Colorectal Cancer Survivors

PURPOSE

Physical activity (PA) is an effective intervention for improving the quality of life of colorectal cancer survivors (CRC) and may reduce the risk of cancer recurrence and cancer specific and all-cause mortality. However, most CRC survivors are not sufficiently active to receive these benefits. Sedentary behavior (SB) has also been linked to morbidity and mortality risk independent of activity level, thereby presenting an additional opportunity to improve health outcomes of CRC survivors. The built environment is known to influence PA and SB; however, little is known about where CRC survivors engage in PA and SB. The objective of this exploratory study was to objectively identify locations where CRC survivors engage in PA and SB in order to inform health promoting interventions.

METHOD

Activity and location of CRC survivors (n = 31) was monitored for 1 week between January 2014 and April 2015 in Nova Scotia, Canada. Bouts of PA and SB were time-matched with GPS data to attribute bouts to specific geographic locations.

RESULTS

Participants' home environment was the main location for both time spent in PA bouts (73.7 %) and time spent in SB bouts (90.5 %).

CONCLUSION

This study is the first to objectively identify environments where CRC survivors are active and sedentary. These findings highlight the importance of considering the home environment when developing intervention strategies to increase PA and reduce SB in CRC survivors.

Systematic review of pre-operative exercise in colorectal cancer patients

The aim of this systematic review was to evaluate the evidence for exercise interventions prior to surgery for colorectal cancer resection. The evidence for use of exercise to improve physical fitness and surgical outcomes is as yet unknown. A systematic search was performed of MEDLINE, EMBASE, CINAHL, AMED and BNI databases for studies involving pre-operative exercise in colorectal cancer patients. Eight studies were included in the review. There is evidence that pre-operative exercise improves functional fitness, and to a lesser extent objectively measurable cardio-respiratory fitness prior to colorectal cancer resection. There is no clear evidence at present that this improvement in fitness translates into reduced peri-operative risk or improved post-operative outcomes. Current studies are limited by risk of bias. This review highlights the common difficulty in transferring promising results in a research setting, into significant improvements in the clinical arena. Future research should focus on which type of exercise is most likely to maximise patient adherence and improvements in cardio-respiratory fitness. Ultimately, adequately powered, randomised controlled trials are needed to investigate whether pre-operative exercise improves post-operative morbidity and mortality.

Factors influencing physical activity behaviors in colorectal cancer survivors

PURPOSE

To elucidate factors that impact intention (INT) to be active as well as actual physical activity (PA) behavior in colorectal cancer survivors (CRC-S) using the theory of planned behavior (TpB). Planning for PA was explored as a mediator of the INT-behavior relationship. Chemotherapy-induced neuropathy and fatigue were also explored.

DESIGN

A cross-sectional quantitative mailed survey was used.

SETTING

The study was conducted among community-dwelling adults living in Pennsylvania when diagnosed with colorectal cancer (CRC).

SUBJECTS

Subjects comprised 843 CRC-S diagnosed with CRC in Pennsylvania in 2009.

MEASURES

The survey included questions about planning for PA, TpB constructs, medical and social variables, and PA as measured by a modified Godin Leisure Time Questionnaire.

ANALYSIS

Descriptive statistics were used to characterize the sample. A mediation analysis was used to determine if planning mediated the relationship between INT and actual PA behavior. A stepwise regression was used to determine predictors of INT and PA.

RESULTS

Ninety-six CRC-S responded, with 25% meeting PA recommendations for health promotion, suggesting that CRC-S are insufficiently active. Perceived behavioral control (PBC) and social norm (SN) accounted for 43% of the variance in INT, whereas 30% of the variance in PA was explained by PBC and age. Neuropathy negatively impacted PA behavior (p = .008). Both action and coping planning partially mediated the INT-behavior relationship (β = 20.08, p = .007; β = 22.85, p = .001, respectively).

CONCLUSION

Survivors at risk for inactivity are those with low PBC, low SN, and neuropathy, and those who are older.

Physical activity, occupational sitting time, and colorectal cancer risk in the Netherlands cohort study

We investigated occupational energy expenditure and sitting time in the longest held job (in men only), nonoccupational physical activity, and former sports participation in relation to colorectal cancer endpoints. The Netherlands Cohort Study includes 120,852 participants who completed a self-administered questionnaire in 1986 when they were aged 55-69 years. By 2002, 1,819 male and 1,366 female colorectal cancer cases were available for case-cohort analyses. In men, higher occupational energy expenditure levels and fewer occupational sitting hours were associated with decreased hazard ratios for colon cancer, particularly distal colon cancer (occupational energy expenditure of ≥12 vs. <8 kJ/minute, hazard ratio (HR) = 0.71, 95% confidence interval (CI): 0.52, 0.97; P for trend = 0.01; occupational sitting hours of <2 vs. 6-8 hours/day, HR = 0.63, 95% CI: 0.48, 0.83; P for trend = 0.001). The median duration of the longest held job for male subcohort members was 29 years. Nonoccupational physical activity was inconsistently associated with colorectal cancer endpoints in men, and it was inversely associated with colon cancer in women, particularly distal colon cancer (>90 vs. ≤30 minutes/day, HR = 0.69, 95% CI: 0.50, 0.96; P for trend = 0.06), and rectal cancer (>90 vs. ≤30 minutes/day, HR = 0.59, 95% CI: 0.39, 0.90; P for trend = 0.02). In conclusion, regular long-term physical activity and fewer sitting hours may protect against colon cancer, particularly distal colon cancer; results for rectal cancer were mixed.

Regulation of colon cancer recurrence and development of therapeutic strategies

Recurrence of colon cancer still remains a major issue which affects nearly 50% of patients treated by conventional therapeutics. Although the underlying causative factor(s) is not fully understood, development of drug-resistance has been associated with induction of cancer stem or stem-like cells (CSCs) which constitute a small sub-population of tumor cells known to be highly resistant to chemotherapy. In fact, the discovery of CSCs in a variety of tumors (including colon cancer) has changed the view of carcinogenesis and therapeutic strategies. Emerging reports have indicated that to improve patient outcomes, conventional anticancer therapies should be replaced with specific approaches targeting CSCs. Thus, therapeutic strategies that specifically target CSCs are being sought to reduce the risk of relapse and metastasis. In order to specifically target colon CSCs (while sparing somatic intestinal stem cells), it is critical to identify unique deregulated pathways responsible for self-renewal of CSCs and colon cancer recurrence. Colon CSCs present a unique opportunity to better understand the biology of solid tumors. Thus, a better understanding of the clinical signs and symptoms of colon cancer patients (undergoing surgery or chemotherapy) during perioperative periods, along with the underlying regulatory events affecting the stem/progenitor cell self-renewal and differentiation of colon epithelial cells, is of immense importance. In this review we discuss the implication of clinical factors and the emerging role of CSCs during recurrence of colon cancer along with the development of new therapeutic strategies involving the use of natural agents.

p53, aerobic metabolism, and cancer

p53 regulates the cell cycle and deoxyribonucleic acid (DNA) repair pathways as part of its unequivocally important function to maintain genomic stability. Intriguingly, recent studies show that p53 can also transactivate genes involved in coordinating the two major pathways of energy generation to promote aerobic metabolism, but how this serves to maintain genomic stability is less clear. In an attempt to understand the biology, this review presents human epidemiologic data on the inverse relationship between aerobic capacity and cancer incidence that appears to be mirrored by the impact of p53 on aerobic capacity in mouse models. The review summarizes mechanisms by which p53 regulates mitochondrial respiration and proposes how this might contribute to maintaining genomic stability. Although disparate in nature, the data taken together suggest that the promotion of aerobic metabolism by p53 serves as an important tumor suppressor activity and may provide insights for cancer prevention strategies in the future.

Clinical trials of antioxidants as cancer prevention agents: past, present, and future

The purpose of this review is to summarize the most important human clinical trials of antioxidants as cancer prevention agents conducted to date, provide an overview of currently ongoing studies, and discuss future steps needed to advance research in this field. To date there have been several large (at least 7000 participants) trials testing the efficacy of antioxidant supplements in preventing cancer. The specific agents (diet-derived direct antioxidants and essential components of antioxidant enzymes) tested in those trials included β-carotene, vitamin E, vitamin C, selenium, retinol, zinc, riboflavin, and molybdenum. None of the completed trials produced convincing evidence to justify the use of traditional antioxidant-related vitamins or minerals for cancer prevention. Our search of ongoing trials identified six projects at various stages of completion. Five of those six trials use selenium as the intervention of interest delivered either alone or in combination with other agents. The lack of success to date can be explained by a variety of factors that need to be considered in the next generation research. These factors include lack of good biological rationale for selecting specific agents of interest; limited number of agents tested to date; use of pharmacological, rather than dietary, doses; and insufficient duration of intervention and follow-up. The latter consideration underscores the need for alternative endpoints that are associated with increased risk of neoplasia (i.e., biomarkers of risk), but are detectable prior to tumor occurrence. Although dietary antioxidants are a large and diverse group of compounds, only a small proportion of candidate agents have been tested. In summary, the strategy of focusing on large high-budget studies using cancer incidence as the endpoint and testing a relatively limited number of antioxidant agents has been largely unsuccessful. This lack of success in previous trials should not preclude us from seeking novel ways of preventing cancer by modulating oxidative balance. On the contrary, the well demonstrated mechanistic link between excessive oxidative stress and carcinogenesis underscores the need for new studies. It appears that future large-scale projects should be preceded by smaller, shorter, less expensive biomarker-based studies that can serve as a link from mechanistic and observational research to human cancer prevention trials. These relatively inexpensive studies would provide human experimental evidence for the likely efficacy, optimum dose, and long-term safety of the intervention of interest that would then guide the design of safe, more definitive large-scale trials.

Importance of frequency, intensity, time and type (FITT) in physical activity assessment for epidemiological research

Physical activity is a multi-faceted behaviour comprised of several components: frequency, intensity, time and type (FITT). Despite this understanding, there is currently a lack of knowledge regarding how the individual components of FITT influence chronic diseases. This is partly due to the tendency for researchers to focus on intensity via obtaining accurate measurements of energy expenditure. Although energy expenditure is an important consideration in the assessment of physical activity, it is only one component. Accordingly, future studies examining the association between physical activity and disease risk would benefit from examining all the components of FITT. Considering that all the components of FITT are modifiable, knowing their independent or combined influence on risk may provide valuable insight for future prevention interventions.

Physical activity and cancer prevention: a systematic review of clinical trials

BACKGROUND

Physically active individuals have lower rates of many cancers and improved cancer outcomes. Controlled exercise trials measuring putative biomarkers of cancer risk are being conducted to further understand the role of exercise in cancer etiology and progression. We aimed to systematically review the effect of exercise on various biomarkers.

METHODS

A comprehensive search strategy identified 353 publications from January 1980 to August 2010. We included those clinical trials of exercise measuring biomarkers following minimum 4-week intervention among cancer survivors or people with one or more cancer risk factors. Two reviewers abstracted data and assessed quality independently. Effect sizes and 95% confidence intervals were estimated.

RESULTS

Four primary prevention and five tertiary prevention trials were included. Exercise had a small to moderate effect on improving concentrations of several blood biomarkers implicated in breast and colon cancer pathways including insulin, leptin, estrogens, and apoptosis regulation. In breast cancer survivors, exercise had a small to moderate effect on improving some biomarkers associated with prognosis including various insulin-like growth factor axis proteins, insulin, and inflammation; and a large effect on enhancing immune function.

CONCLUSION

Data are few, but there is some evidence to support the role of exercise in modulating various cancer pathways.

Physical activity and gastrointestinal cancer prevention

Colorectal cancer is the third most common cancer globally and is a leading cause of cancer death. Gastric cancer contributes significantly to the global cancer burden, particularly in low- and middle-income countries. We reviewed the literature for studies on physical activity or exercise and colon, rectal, and gastric cancers as well as colonic adenomatous polyps. We identified 52 studies of colon cancer, 31 studies of rectal cancer, 23 studies of colon polyps, and 16 studies of gastric cancer. Of the 52 studies of physical activity and colon cancer, 37 found a statistically significant association between increased levels of physical activity and decreased colon cancer risk in at least one comparison. Accumulated evidence suggests that physical activity is associated with a 25% reduction in colon cancer risk. In line with previous reports, we found no indication that the association was more pronounced for occupational versus recreational physical activity, with both resulting in a risk reduction of about 22%. Evidence for other domains of physical activity (i.e., transportation or household physical activity) is limited. Evidence is emerging that individuals who are consistently active across the lifetime may obtain greater risk reductions than those who are only active in recent years. Despite consistent associations with colon cancer, evidence is more limited though suggestive that physical activity reduces risk of colon adenomas or adenoma recurrence. There is clear evidence that physical activity is not associated with rectal or gastric cancers.

Physical activity in the prevention and treatment of colorectal carcinoma

BACKGROUND

Colorectal carcinoma is the most common type of tumor in Western countries. The risk of developing colorectal carcinoma depends both on genetic factors (familial predisposition) and on lifestyle-related factors such as body-mass index, level of physical activity, and nutritional behavior. Regular physical activity is important in primary prevention, and there is also evidence that the prognosis after treatment of a colorectal carcinoma can be improved by exercise.

METHODS

The PubMed database was searched for relevant articles that appeared in the last 10 years, and selected articles were evaluated.

RESULTS

Cross-sectional studies have shown that regular physical activity (ca. 7 hours of brisk walking per week) lowers the risk of colon carcinoma by 40%. Physical activity also improves the outcome of patients already diagnosed with colorectal carcinoma: for example, patients with advanced disease (UICC stage II or III) have been found to survive significantly longer if they perform 4 hours of brisk walking per week, or the equivalent degree of physical exercise.

CONCLUSIONS

Cross-sectional studies show that physically active persons are less likely to develop colorectal carcinoma than physically inactive persons, and that they have better outcomes in the event that they do develop the disease. The positive findings with respect to secondary prevention still need to be confirmed in interventional trials, but in primary prevention, at least, physical activity should be actively promoted, along with other beneficial lifestyle habits and screening measures.

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

OBJECTIVE

Increased physical activity may decrease the risk of colorectal cancer. As a prerequisite to the determination of lifestyle attributable risks, we performed a systematic review and meta-analysis of prospective observational studies to quantify gender-specific risk associated with increased leisure-time physical activity (LT-PA).

METHOD

We searched MEDLINE and EMBASE (to December 2007), and other sources, selecting reports based on strict inclusion criteria. We used random-effects meta-analyses to estimate summary risk ratios (RR) and 95% confidence intervals (95% CI) for uppermost vs lowermost categories of physical activity. To investigate dose-response, we explored risks ratios as a function of cumulative percentiles of physical activity distribution.

RESULTS

Fifteen datasets from 14 articles, including 7873 incident cases, were identified. For colon cancer, there were inverse associations with LT-PA for men (RR: 0.80; 95% CI: 0.67-0.96) and women (0.86; 0.76-0.98). LT-PA did not influence risk of rectal cancer. The dose-response analysis was consistent with linear pattern reductions in risk of colon cancer in both genders. There was evidence of moderate between-study heterogeneity but summary estimates were broadly consistent across potential confounding factors.

CONCLUSION

Increased LT-PA is associated with a modest reduction in colon but not rectal cancer risk; a risk reduction, which previously may have been overstated. LT-PA only interventions in public health cancer prevention strategies are unlikely to impact substantially on colorectal cancer incidences.

[Prescribing exercise in tobacco smoking cessation therapy]

Tobacco is one of the main causes of mortality in industrialized countries, yet there is no treatment that is wholly efficacious for helping smokers to quit the habit. Physical exercise is one of the low-cost nonpharmacologic strategies in rehabilitation therapies in several diseases and its practice offers a way of combating the harmful effects of smoking on health. Studies have shown that physical exercise helps reduce the intensity of some of the main symptoms that may arise when a smoker attempts to quit, yet doctors and sport therapists are generally unaware of this benefit and do not know how to prescribe exercise appropriately. This study aims to present the reasons why physical exercise should be considered as a useful nonpharmacologic aid in combatting the symptoms of smoking and smoking cessation, to review the relevant literature, and to outline basic guidelines that might serve to orient the prescription of physical exercise for smokers attempting to quit.

Cardiorespiratory fitness and digestive cancer mortality: findings from the aerobics center longitudinal study

Although higher levels of physical activity are inversely associated with risk of colon cancer, few prospective studies have evaluated overall digestive system cancer mortality in relation to cardiorespiratory fitness (CRF). The authors examined this association among 38,801 men ages 20 to 88 years who performed a maximal treadmill exercise test at baseline in the Aerobics Center Longitudinal Study (Dallas, TX) during 1974 to 2003. Mortality was assessed over 29 years of follow-up (1974-2003). Two hundred eighty-three digestive system cancer deaths occurred during a mean 17 years of observation. Age-adjusted mortality rates per 10,000 person-years according to low, moderate, and high CRF groups were 6.8, 4.0, and 3.3 for digestive system cancer (P(trend) < 0.001). After adjustment for age, examination year, body mass index, smoking, drinking, family history of cancer, personal history of diabetes, hazard ratios (95% confidence intervals) for overall digestive cancer deaths for those in the middle and upper 40% of the distribution of CRF relative to those in the lowest 20% were 0.66 (0.49-0.88) and 0.56 (0.40-0.80), respectively. Being fit (the upper 80% of CRF) was associated with a lower risk of mortality from colon [0.61 (0.37-1.00)], colorectal [0.58 (0.37-0.92)], and liver cancer [0.28 (0.11-0.72)] compared with being unfit (the lowest 20% of CRF). These findings support a protective role of CRF against total digestive tract, colorectal, and liver cancer deaths in men.

Recreational physical activity modifies the association between a common GH1 polymorphism and colorectal cancer risk

Growth hormone may be associated with the development of colorectal cancer directly and/or indirectly via increased serum level of insulin-like growth factor (IGF-I). Regular physical activity can decrease insulin resistance and modulates IGF-I production. A common polymorphism in the GH1 gene, rs2665802, was previously shown to be associated with lower IGF-I levels and decreased colorectal cancer (CRC) risk. We investigated the association of this polymorphism and physical activity with colorectal cancer risk in a case-control study.

METHODS

The analysis includes 3,041 (1,402 cases and 1,639 controls) participants in the Molecular Epidemiology of Colorectal Cancer study, a population-based case-control study in Northern Israel. Analysis was carried out separately in two sets. The first set included 1,248 subjects (625 cases, 623 controls), and the second validation set consisted of 1,793 subjects (777 cases, 1,016 controls).

RESULTS

No association was found between the studied polymorphism and CRC risk. However, evaluation of gene environment interactions revealed an interaction between leisure time physical activity and the GH1 polymorphism, which was consistent in both sets (P(interaction) = 0.005). The genotype AA was associated with decreased risk of CRC among individuals who did not engage in any such activity (odds ratio, 0.76; 95% confidence interval, 0.52-0.98), whereas the same genotype was marginally associated with increased risk among individuals who reported physical activity (odds ratio, 1.38; 95% confidence interval, 0.98-1.94).

CONCLUSIONS

We found that the A allele of the rs2665802 polymorphism is associated with reduced risk of CRC only among physically inactive individuals, indicating an interaction between physical activity and the growth hormone/IGF-I system. A replication of the observed findings and further investigation of the underlying mechanism is warranted.

Exercise in prevention and management of cancer

OPINION STATEMENT

Regular and vigorous physical exercise has been scientifically established as providing strong preventative medicine against cancer with the potential to reduce incidence by 40%. The effect is strongest for breast and colorectal cancer; however, evidence is accumulating for the protective influence on prostate cancer, although predominantly for more advanced disease and in older men. Following cancer diagnosis, exercise prescription can have very positive benefits for improving surgical outcomes, reducing symptom experience, managing side effects of radiation and chemotherapy, improving psychological health, maintaining physical function, and reducing fat gain and muscle and bone loss. There is now irrefutable evidence from large prospective studies that regular exercise postdiagnosis will actually increase survivorship by 50%-60% with the strongest evidence currently for breast and colorectal cancers. In our work with prostate cancer patients, we have found that exercise can limit or even reverse some of the androgen deprivation therapy (ADT) adverse effects by increasing muscle mass, functional performance, and cardiorespiratory fitness without elevating testosterone levels. Hormone therapies for breast and prostate cancer can result in alarmingly increased risk of cardiovascular disease, obesity, type 2 diabetes, osteoporosis, and sarcopenia. Increasingly, patients are questioning the benefit of some cancer treatments as the risk of morbidity and mortality from other chronic diseases begins to outweigh the initial cancer diagnosis. Over three decades of research in exercise science and many hundreds of RCTs demonstrate the efficacy of appropriate physical activity for preventing and managing these secondary diseases. Based on this evidence it is now clear to us that exercise is a critical adjuvant therapy in the management of many cancers and will greatly enhance the therapeutic effects of traditional radiation and pharmaceutical treatments by increasing tolerance, reducing side effects, and lowering risk of chronic diseases, even those not aggravated by cancer treatment. While patients and their clinicians deal with their cancer, other chronic disease mechanisms continue unabated. Anxiety, depression, poor nutritional choices, and a counterproductive rest strategy will accelerate these processes, while a well-designed exercise program adhered to by the patient and supported by the medical and exercise professionals will effectively control and even reverse these diseases and disabilities. In the wide range of cancer populations that we work with, both young and old and with curative and palliative intent, our overwhelming experience is that exercise is first well tolerated, and benefits the patientpsychologically and physically. While some of our patients are on individual, home-based programs, we find that small group exercise sessions with close supervision by Exercise Physiologists (EP) provides a more motivating setting and the social interaction is critical for adherence and retention as well as greater psychological benefits such as reduced anxiety and depression and enhanced social connectedness. While managing many hundreds of cancer patients over the last 6 years, our clinic has not experienced any instances of the exercise hindering patient recovery or treatment purpose, nor have any significant injuries occurred. However, it is critical that the exercise prescription and management be tailored to the individual patient and that they are monitored by appropriately trained and professionally accredited exercise specialists. For those patients at low exercise risk and without significant musculoskeletal issues, community-based physical activity is of excellent benefit where the emphasis should be on adherence, affordability, convenience, and enjoyment.

Physical activity, sedentary behavior, and the risk of colon and rectal cancer in the NIH-AARP Diet and Health Study

OBJECTIVE

In order to prospectively investigate physical activity at varying intensities and sedentary behavior in relation to colorectal cancer.

METHODS

We considered 488,720 participants of the NIH-AARP Diet and Health Study who were aged 50-71 years at baseline in 1995-1996. Through 31 December, 2003, we identified 3,240 and 1,482 colorectal cancers among men and women, respectively. We estimated multivariable relative risks (RR) and 95% confidence intervals (CI) of colorectal cancer using Cox regression.

RESULTS

Engaging in exercise/sports five or more times per week compared to never or rarely exercising was associated with a reduced risk of colon cancer among men (p = 0.001; RR = 0.79, 95% CI = 0.68-0.91) and a suggestive decrease in risk among women (p = 0.376; RR = 0.85, 95% CI = 0.70-1.04). Engaging in exercise/sports was also associated with a decreased risk of rectal cancer in men (P = 0.074; RR comparing extreme categories = 0.76, 95% CI = 0.61-0.94). In men, we observed inverse relations of both low intensity (p = 0.017; RR = 0.81, 95% CI = 0.65-1.00 for > or =7 h/week) and moderate to vigorous intensity activity (p = 0.037; RR = 0.82, 95% CI = 0.67-0.99 for > or =7 h/week) to colon cancer risk. In contrast, sedentary behavior (time spent watching television/videos) was positively associated with colon cancer (p < 0.001; RR = 1.61, 95% CI = 1.14-2.27 for > or =9 h/day) among men. Similar, but less pronounced relations were observed in women.

CONCLUSION

Engaging in physical activity of any intensity is associated with reductions in colon and rectal cancer risk. Conversely, time spent sedentary is associated with increased colon cancer risk.