Behavioral approaches to cancer prevention
Errol J. Philip, PhD 
Jamie S. Ostroff, PhD
Overview
Certain health behaviors increase the risk of being diagnosed with cancer. It has been estimated that 35% of cancer deaths throughout the world could be avoided through adoption of health promoting behaviors. This chapter summarizes research on the effects of behavioral risk factors on cancer incidence and behavioral interventions for cancer prevention. Several behavioral risk factors-tobacco use, unhealthy diet, sedentary lifestyle and obesity, sun and UV exposure-have all been associated with cancer etiology, and clinical recommendations for health promoting behavior change interventions have been developed. Physician recommendations and delivery of health promotion counseling are essential for effective dissemination of cancer prevention efforts.
Tobacco use
Tobacco use remains the leading preventable cause of morbidity and mortality. In the United States, tobacco use is responsible for nearly one in five deaths or roughly 480,000 early deaths each year (US Surgeon General Report 2014). Tobacco use accounts for at least 30% of all cancer deaths, causing 87% of lung cancer deaths in men and 70% of lung cancer deaths in women. (Source: Cancer Facts & Figures 2014.) In addition to lung cancer, cigarette smoking also increases the risk for cancers of the oral cavity, larynx, pharynx, esophagus, stomach, liver, pancreas, kidney, bladder, cervix, colon/rectum, and acute myeloid leukemia. (Source: Cancer Facts & Figures 2014.) Secondhand smoke exposure is also considered a risk factor for lung cancer with about 3400 nonsmoking adults dying each year of lung cancer as a result of breathing secondhand smoke. (Sources: Cancer Facts & Figures 2014; SGR, 2014.) Cigar smoking causes cancers of the lung, mouth, throat, larynx, and esophagus. (Source: CDC, Consumption of Cigarettes and Combustible Tobacco—United States, 2000–2011, 2012.) Smokeless tobacco products increase the risk of developing cancer of the mouth and throat, esophagus, and pancreas.
Although cigarette use has declined dramatically since the release of the first US Surgeon General’s Report on Smoking and Health in 1964, 18.1% of all adults or more than 42 million American adults currently smoke cigarettes. (Source: CDC, Current cigarette smoking among adults—United States, 2005–2012, 2014.) In 2012, approximately 20.5% of men and 15.8% of women were considered to be current cigarette smokers. African Americans, Native Americans, individuals with lower income, lower education, sexual minorities, and those with comorbid substance abuse and mental illness are more likely to be current smokers. Fortunately, daily consumption of cigarettes has declined with about 22% of smokers reporting nondaily smoking. (Source: CDC, Current cigarette smoking among adults—United States, 2005–2012, 2014.)
Fortunately, there have also been noteworthy declines in youth smoking. In 1997, nearly half (48%) of male high school students and more than one-third (36%) of female students reported using some form of tobacco—cigarettes, cigars, or smokeless tobacco—in the past month. In 2012, tobacco use declined to 23% for male students and 18% for female students. (Sources: Cancer Facts & Figures 2010; CDC, Tobacco Product Use Among Middle and High School Students—United States, 2011 and 2012, 2013.) On the other hand, there are growing concerns about the increasing use of electronic cigarettes, hookah, and other noncigarette tobacco products.1, 2
Tobacco cessation in health care settings
Most recently updated in 2008 and representing current best practices, the US Public Health Service Treating Tobacco Use and Dependence Clinical Practice Guideline (PHS Guideline)3 recommends that evidence-based tobacco treatment be delivered to all smokers in health care settings.
Brief counseling
The PHS Guideline recommends the use of a brief counseling method. As shown in Table 1, physicians are encouraged to: ask, assess, advise, assist, and arrange. Health care providers are encouraged to ask their patients about their smoking status at every encounter. Once current smokers are identified, clinicians should assess readiness to quit to inform the tobacco treatment plan. Clinicians should strongly advise their patients against smoking, personalizing the cancer and other risks of persistent smoking and the benefits of cessation in relation to their patients’ disease and treatment. The next A, assist, involves providing education, addressing barriers to quitting such as concerns about coping, suggesting behavioral strategies that may help them overcome these barriers, developing a quit plan, and prescribing pharmacotherapy as needed. For patients who are reluctant to quit, clinicians should provide motivational counseling in an effort to encourage them to cut down or reduce their daily cigarette consumption. Finally, clinicians are encouraged to arrange follow-up support such as referring smokers to other resources such as Quitlines or onsite tobacco treatment specialists.
Table 1 The “5 A’s” model for treating tobacco use and dependence
| Ask about tobacco use | Identify and document tobacco use status for every patient at every visit (Strategy A1) |
| Advise to quit | In a clear, strong, and personalized manner, urge every tobacco user to quit (Strategy A2) |
| Assess willingness to make a quit attempt | Is the tobacco user willing to make a quit attempt at this time? (Strategy A3) |
| Assist in quit attempt | For the patient willing to make a quit attempt, offer medication and provide or refer for counseling or additional treatment to help the patient quit (Strategy A4) For patients unwilling to quit at the time, provide interventions designed to increase future quit attempts (Strategies B1 and B2) |
| Arrange follow-up | For the patient willing to make a quit attempt, arrange for follow-up contacts, beginning within the first week after the quit date (Strategy A5) For patients unwilling to make a quit attempt at the time, address tobacco dependence and willingness to quit at the next clinic visit |
Pharmacotherapy
The guidelines strongly recommend use of pharmacotherapy along with counseling in order to optimize cessation outcomes. There are several safe and effective medications indicated for smoking cessation: nicotine replacement therapies (NRT) (patch, gum, lozenge, nasal spray, and inhaler), bupropion (Wellbutrin), and varenicline (Chantix). Refer to Table 2 for list of cessation medications, dose, duration, potential contraindications, and side effects. Combination and extended use pharmacotherapy have been shown to enhance effectiveness of tobacco dependence treatment. More research is needed to identify methods for personalizing treatments, including the tailoring of interventions to the smoker’s readiness to quit, sociocultural factors, gender, age, and health status. Neuroscience research focusing on the genetic basis of nicotine addiction may also lead to the development of precision interventions for high-risk groups.
Table 2 Tobacco treatment pharmacotherapy guidelines
| Pharmacotherapy | Dosage | Duration | Availability | Precautions/contraindications | Adverse effects | Patient education |
| If smoking 11 cig/day or >:
If smoking 10 cig/day or <:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
|
|
|
|
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Currently, there is much debate and little data as to whether e-cigarettes will facilitate or impede smoking cessation and reduction of known hazards of traditional cigarettes and other combustible tobacco products.4 The American Society of Clinical Oncology and the American Association of Cancer Research have recently published a literature summary and policy statement5 about electronic cigarettes. Oncologists should advise smokers to quit smoking traditional cigarettes, encourage use of FDA (Food and Drug Administration)-approved cessation medications, refer patients for tobacco cessation counseling, and provide education about the potential risks and lack of known benefits of e-cigarette use with regard to long-term cessation.
Prevention of tobacco use
Preventing tobacco-related cancers requires the development and implementation of effective multipronged tobacco prevention programs. In the most recent Best Practices for Comprehensive Tobacco Control Programs,6 the Centers for Disease Control and Prevention (CDC) recommends statewide programs that combine community-based interventions that focus on (1) preventing initiation of tobacco use among youth and young adults through tobacco control policies (i.e., taxation, tobacco-free laws), (2) promoting quitting among adults and youth, (3) eliminating exposure to secondhand smoke, and (4) identifying and eliminating tobacco-related disparities among population groups. Tobacco prevention programs should also consider targeting those children with highest biological susceptibility and sociocultural factors that increase the risk for initiating regular smoking.
Secondary and tertiary cancer prevention
An emerging body of evidence demonstrates that for individuals diagnosed with cancer, smoking is also associated with several adverse outcomes such as increased complications from surgery, increased treatment-related toxicity, decreased treatment effectiveness, poorer quality of life, increased risk of recurrence, increased risk of second primary tumors, increased noncancer-related comorbidity and mortality, and decreased survival.7–9 Despite these risks, at least 15.1% of all adult cancer survivors report current cigarette smoking.10 Continued tobacco use after diagnosis and resumption of smoking after initial quit attempt should be seen as a modifiable clinical problem. In fact, there is a growing consensus among oncology leadership organizations that tobacco use assessment and treatment should be treated as a quality of care metric.11–14 Unfortunately, a recent survey of practicing oncologists showed that oncologists provide quitting advice to only 25% of their patients15 and that only half of National Cancer Institute-designated Comprehensive Cancer Centers offer any type of tobacco treatment program.16 These survey findings highlight the need to identify and address barriers to tobacco treatment delivery in cancer care. Barriers to addressing tobacco use include patient factors (shame, helplessness, addiction), physician barriers (lack of training and referral options, beliefs about patients’ lack of interest or ability to quit), and systems levels factors (inadequate identification of smokers, costs) that impede the delivery of effective tobacco programs.17 Further research examining patient, provider, and systems-level strategies for engagement and retention of smokers into evidence-based tobacco treatment is needed.
Energy balance: diet, physical activity, and body weight
Energy balance represents the nexus of diet, physical activity, and body weight and has been shown to be a significant contributor to the global burden of cancer. Although research is ongoing concerning the mechanisms by which these factors relate to cancer and cancer outcomes, there is strong evidence to support an association between energy balance and cancer development and progression.
Obesity and dietary factors are estimated to account of nearly 35% of cancer cases in the United States. Strong evidence exists regarding an association between excess weight and an increased risk of many common cancer types, as well as emerging evidence of a link to poorer disease outcomes. The greatest consistency in research examining diet and cancer has been established in regard to broader dietary patterns, with prudent plant-based diets that limit meat and dairy intake generally associated with reduced cancer risk. Engagement in physical activity has been consistently shown to confer a protective effect across common cancer types.
This expansive literature has provided a foundation for lifestyle-based cancer prevention and control guidelines that all patients and survivors should be encouraged to adopt. These include consuming a healthy diet, maintaining or achieving a normal weight, and engaging in regular physical activity, all of which are key components to both cancer prevention and the pursuit of long-term health among those diagnosed with cancer.
Excess weight remains a critical modifiable risk factors linked to cancer risk in the United States,18, 19 with further contributions from physical inactivity and dietary factors. These three interrelated factors, collectively referred to as energy balance, represent primary targets of investigation and intervention in cancer prevention and control. An extensive body of research exists concerning components of energy balance and their association with increased risk of primary and secondary cancers, treatment complications, impaired quality of life, and poorer disease outcomes.20
Lifestyle behavior guidelines have been published by national organizations targeting cancer prevention and control. The American Cancer Society notes the importance of maintaining a healthy weight, adopting a healthy diet and engaging in regular exercise.21, 22 These recommendations are summarized in Table 3. Importantly, the broad nature of these recommendations align with disease prevention guidelines beyond cancer, and adhering to such advice will serve to also reduce risk of other chronic conditions such as cardiovascular disease, diabetes, and hypertension. Unfortunately, despite a variety of efforts to raise awareness of lifestyle-based recommendations and increase adoption, adherence among the general population and cancer survivors alike remains low.23, 24 Recent calls have been made to promote the use of the term energy balance in clinical practice and oncology,25 thus reinforcing the interdependent nature of diet, exercise, and weight, and in turn lessen the potential for patients to focus on such factors in isolation.
Table 3 ACS adult guidelines for energy balance for cancer prevention and control
| Achieve and maintain healthy weight |
|
| Engage in regular physical activity |
|
| Maintain a healthy diet |
|
A recent study of nearly 112,000 nonsmoking individuals examined the association between adherence to ACS health guidelines and disease outcomes across 14 years of follow-up. The authors reported that greater adherence to health recommendations were associated with reduced risk of both cancer and all-cause mortality.26 The next section will provide an overview of current research findings concerning the relationship between energy balance and cancer. While acknowledging the synergistic and interrelated nature of diet, weight, and physical activity, each will be addressed separately with focus given to the four most common cancers diagnosed in the United States.
Diet and cancer
Breast cancer
The potential association between diet and breast cancer has received extensive empirical attention over the past three decades. The WCRF (World Cancer Research Fund) reported that based on observational studies, certain dietary patterns that include a high intake of fruit and vegetables, along with consumption of poultry, fish, and low-fat dairy products,27 are associated with reduced disease risk. Similar findings were reported by Brennan et al. in a 201028 systematic review and meta-analysis of 39 case-control and cohort studies examining various dietary patterns. Despite its primary role among prudent dietary patterns, little evidence exists supporting the isolated protective effect of fruit and vegetable intake alone.29 The Women’s Health Initiative Trial sought to establish whether reduced fat intake could impact cancer risk in a randomized clinical trial involving nearly 50,000 postmenopausal women. Reduction in fat intake was associated with only a marginal reduction in disease risk, and no difference in invasive breast cancer cases during the 8-year follow-up period.30 Finally, evidence suggests that alcohol consumption may increase risk of breast cancer in a dose–response manner for both pre and postmenopausal women,27, 29 while a recent meta-analysis suggested that there currently exists no evidence linking red meat consumption with breast cancer risk across the lifespan.31
Prostate cancer
As the literature examining the relationship between diet and prostate cancer has matured, recent studies have suggested that this association may differ based on the aggressiveness of the disease. In their systematic review, Ma and Chapman32 proposed that further work is needed to account for this potential influence, and that there is not yet sufficiently rigorous evidence to provide firm recommendations on the role of diet in prostate cancer. Despite this, there exists suggestive evidence of a protective effect of vegetable and soy consumption, and an increased risk of disease associated with dairy products. Kirsh et al.33 reported that men who had a high intake of cruciferous vegetables (e.g., cabbage, broccoli) had a decreased risk of aggressive prostate cancer. Dairy consumption may lead to a possible increased risk of prostate cancer,27 with a further analysis of the PLCO trial, and nearly 30,000 men establishing a modest increase in the risk of nonaggressive cancers among those reporting a higher intake of dairy products.34 There was no association established between dairy intake and more aggressive forms of disease.
Colorectal cancer
Considerable effort has been devoted to examine the potential impact of nutrition on the development and progression of colorectal cancer. A number of recent international reports and meta-analyses noted convincing evidence of an increased risk of colon, colorectal, and rectal cancer associated with the consumption of red meat and processed meat products.27, 35 These recent studies, including an updated meta-analysis,36 noted a dose–response relationship between meat consumption and cancer risk, including a 21% increased risk with 50 g/day consumed and a 29% increased risk with 100 g/day consumed.35 For comparative purposes, the recommended serving size for a portion of lean meat is approximately 85 g.
The relationship between fiber and disease risk has also received considerable attention; however, despite plausible biological mechanisms, early reports found little evidence of an association between fiber consumption and colorectal cancer.37–39 More recent studies have, however, noted a relationship.40, 41 A systematic review of 25 prospective studies reported a dose–response relationship between cereal fiber and whole grains and a reduced risk of colorectal cancer.42 The authors reported a statistically significant 10% decrease in cancer risk with 10 g of daily fiber intake. The recommended daily intake of fiber for adults is 25 g.
Alcohol consumption has also been associated with increased risk of colorectal cancer.35 In a review of 103 cohort studies, Huxley found that those reporting the highest levels of alcohol consumption had a 60% increased risk of colorectal cancer compared to non- or light drinkers. This relationship was particularly prominent among male participants.43 Chung et al.44 conducted a systematic review and reported inconsistent results concerning the relationship between calcium and vitamin D and colorectal cancer. Importantly, while evidence is evolving and currently suggests that increased calcium intake could reduce risk of colorectal cancer; this benefit must be weighed against potential increase in prostate cancer risk. At present, there exist no recommendations to increase calcium intake as a means of reducing cancer risk.
Lung cancer
The WRCF/AICR (American Institute for Cancer Research) report established that higher rates of fruit and vegetable consumption is consistently associated with reduced risk of lung cancer among both smokers and nonsmoking populations.27 The report notes, however, that despite this consistency, the protective effect of a healthy diet is minimal compared to risk associated with tobacco use.
Obesity and cancer
Obesity rates have increased dramatically over the past 30 years, with over 35% of US adults now considered obese.45 A 2003 report estimated 14–20% of all cancer deaths to be attributable to excess weight,46 and in combination with the dietary intake, accounts for nearly one in three cancers and may soon overtake tobacco as the primary modifiable risk factor in cancer.27, 47 The unprecedented increase in weight of the general population, along with the increased risk of cancer associated with excess weight, means that an estimated 10 of the 14 million survivors are overweight or obese.48–50 A report published by the WCRF/AICR, along with an updated review by Renehan in 2008, noted evidence of a link between excess body weight and many common types of cancer.27, 51 These include colon, kidney, pancreatic cancer, and esophageal adenocarcinoma among both sexes, as well as thyroid cancer for men and gallbladder, endometrial, ovarian, and postmenopausal breast cancers among women.
Breast and Prostate Cancer
Excess body weight and weight gain in adulthood have both been consistently associated with risk of breast cancer.52, 53 A further meta-analysis by Vrieling et al.54 noted a stronger association between weight gain and estrogen-/progesterone-positive breast cancers. The impact of obesity on prostate cancer appears to be moderated by disease severity, and thus, more recent studies have emphasized the importance of examining this relationship in greater detail. Obese weight status has been associated with greater risk of being diagnosed with advanced disease,55 increased risk of recurrence,56 and poorer prognosis.57 In contrast, Wright et al.58 reported an inverse association between BMI (body mass index) and risk of early stage disease among a large population of men enrolled in the National Institutes of Health–AARP Diet and Health Study. This complex relationship is believed to be partly due to challenges inherent to screening and diagnosis among obese men, however, research continues.
Colorectal cancer and other notable findings
The majority of studies have supported a positive association between weight and risk of colorectal cancer, most strongly among men,35, 46 including a recent meta-analysis over 56 observational studies.59 Norat et al.35 noted that this association was more consistent among studies that examined measures of body fat distribution beyond BMI, with excess weight in the abdominal region most predictive of increased cancer risk.
Endometrial cancer remains the most consistent cancer linked to excess weight, with an estimated 60% of new cases attributable to obesity.60 Obese women are 2–3.5 times more likely to be diagnosed with this form of cancer,61 including a large-scale European study that followed one million women for nearly 40 years reporting obese women to be 2.5 times more likely to be diagnosed with cancer of the uterine corpus compared to those of normal weight.62
Physical activity and cancer
Engagement in physical activity remains an important component of health recommendations and has been associated with reduced risk across a number of common cancer types.22
Breast and prostate cancer
The association between physical activity and breast cancer risk has been extensively researched and deemed convincing.63 This has included a review of more than 70 observational reports that established an absolute risk reduction of between 20% and 30% in breast cancer risk when comparing those who were most active to those who are least active.61, 64 In a systematic review and meta-analysis of over 40 reports, including over two million men and nearly 90,000 cases of cancer, Liu et al.65 reported an 10% overall risk reduction in prostate cancer associated with engagement in physical activity.
Colorectal and lung cancer
The relationship between physical activity and colorectal cancer has also received considerable empirical attention. A 2009 meta-analysis by Wolin et al.66 examined over 50 studies and reported on overall reduction in risk of 24%, with greater risk reduction reported in case-control studies. Similar findings were reported by Harris and Thune in relation to colon cancer, including evidence of a dose–response relationship between physical activity engagement and cancer risk among both genders.67, 68 No evidence of a relationship was established, however, among seven studies of rectal cancer.
In a review of predominantly cohort studies, Emaus and Thune69 reported a 23% reduction in lung cancer risk among those engaged in physical activity, with a greater rate of 38% once again reported among case-control studies. A further meta-analysis reported similar results, although risk reduction varied based on intensity of activity, with moderate engagement associated with a 13% reduction in risk and rigorous activity associated with 30% reduction in risk.70 A recent systematic review noted the need for ongoing research in this arena, particularly among women, with 10 studies reporting an inverse association between physical activity and lung cancer and nearly as many reporting a null association.71
Energy balance and cancer survivorship
As survival rates across many common cancers have increased; emerging research has begun to address the role of lifestyle in cancer prognosis and survivorship. Research and clinical programs in this domain have sought to build upon the noted potential for a cancer diagnosis to act as a teachable moment,72 and to thus seize upon a period in which patients and survivors may be motivated to enact lifestyle changes.73–75 In a systematic review of physical activity and cancer survival, authors reported, among 27 published studies, there was sufficient evidence supporting an association between physical activity and a reduction in all-cause mortality, as well as breast and colon-specific cancer mortality.76 In a review by Davies et al.,77 a healthy or prudent diet pattern low in fat and high in fiber may be broadly associated with a reduced risk of cancer recurrence and progression; however, further research is needed. This is particularly true in regard to establishing whether the protective effects of a healthy diet and/or physical activity may be due to their promotion of a healthy body weight. Finally, Parekh et al.78 reported in a systematic review of the literature pertaining to breast, colon, and prostate cancer that the majority of studies suggest a negative effect of excess weight on cancer survival outcomes. However, the authors noted that breast cancer is overrepresented in this literature, and that many studies examining obesity and cancer survival were not initially designed to examine such outcomes. In light of these emerging findings, the American Society of Clinical Oncology has created a toolkit to help oncologists counsel their patients about the importance of weight management for cancer survivors.79
Promoting behavioral change in diet and physical activity
Although some individuals may require more intensive intervention, a recommendation from a health care provider can play an important role in promoting energy balance and lifestyle change.20 Evidence-based behavioral lifestyle programs exist for those individuals who require more support. These 6–12-month programs usually adopt a group-based format and include dietary counseling and caloric reduction, along with promotion of physical activity engagement. Such programs routinely result in weight loss of 5–10% of initial body weight80 and can provide clinically relevant improvements in many disease markers with plausible downstream benefits for reducing cancer risk.81, 82 Maintenance of weight loss remains a challenge and providers should remain supportive of patients seeking to adopt changes.83 Evidence pertaining to the impact of behavior change on cancer-related outcomes is growing, with evidence suggesting that bariatric surgery results in reduced cancer risk84 and that changes in diet and physical activity behavior change can improve biological markers among survivors.85
Risk behaviors for skin cancer
Skin cancers are commonly divided into melanoma and nonmelanoma skin cancers. Melanoma is less common but more aggressive than other types of skin cancer, affecting some 68,000 Americans each year.86 Exposure to ultraviolet radiation (UVR) from the sun or from indoor tanning devices is a significant risk factor for skin cancer,87 and there are well-established behavioral strategies for skin cancer prevention. These recommendations,88 include nonuse of artificial tanning beds and limiting unprotected exposure to the sun—especially strong midday sunlight—whenever possible. When exposure to sunlight is not avoidable, individuals should be advised to apply a broad spectrum sunscreen (i.e., effective against both UVA (ultraviolet A) and UVB (ultraviolet B) radiation with a sun protection factor (SPF) of 30 or greater) very liberally, approximately 30 min before going out into the sunlight and then reapplying every 2 h or after any exposure to water. Most importantly, individuals should be advised that sunscreens offer only partial protection from UVR and should best be used in combination with avoiding exposure to strong sunlight and wearing sun protective clothing (i.e., hats, long-sleeved garments).
Unfortunately, only 30% of US adults routinely report using sunscreen and/or sun protective clothing.89 Remarkably, surveys show that even cancer survivors do not consistently protect themselves from UV light, especially younger survivors who are most likely to be exposed to UVR.50, 90, 91
Summary
The importance of reducing behavioral risks on cancer prevention is well established.92 Healthy People 202093 goals emphasize health promoting behavior change efforts such as not smoking, maintaining a healthy weight, eating a low-fat, high-fiber diet, being physically active, and limiting UVR exposure.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
