Many of the greatest reductions in cancer morbidity and mortality are a result of advances in cancer prevention and early detection. These advances were enabled by translating the discoveries of the causes and progressive nature of cancer into effective new clinical practices and public education and policy initiatives.Central to preventing cancer is the identification of factors that increase a person’s risk of developing cancer and eliminating or reducing these factors where possible (see Figure 4). As research has enhanced our knowledge of cancer risk factors, we have learned that more than 50 percent of the 585,720 cancer deaths expected to occur in the United States in 2014 will be related to preventable causes (16).Many factors that increase the risk of developing cancer are related to lifestyle; thus, adopting a healthy approach to living, where possible, can eliminate or reduce the risk of some cancers (seeFigure 5). Moreover, many healthy approaches to living can also reduce cancer recurrence and improve outcomes following a cancer diagnosis. However, a great deal more research and many more resources are needed to understand how best to help individuals change their lifestyle.
Adopting Healthy Approaches to Living
Tobacco use is responsible for almost 30 percent of cancer deaths each year in the United States (1) (see Figure 6). As a result, one of the most effective ways a person can lower the risk of developing cancer is to eliminate tobacco use (see sidebar on Reasons to Eliminate Tobacco Use). This relationship between tobacco use and cancer was first brought to the public’s attention 50 years ago, when the U.S. Surgeon General’s report on “Smoking and Health” was published (17). Since then, smoking rates among U.S. adults have more than halved, and as a result, an estimated 800,000 deaths from lung cancer were avoided between 1975 and 2000 (18).Unfortunately, the rate of decline in smoking prevalence in the United States has slowed in recent years (18). In fact, almost 70 million individuals age 12 or older are regular users of tobacco products (20).If we are to eradicate one of the biggest threats to public health, researchers, clinicians, advocates, and policymakers must continue to work together. Several steps that could be taken to achieve this goal are outlined in this year’s Surgeon General’s report, “The Health Consequences of Smoking—50 Years of Progress,” (see sidebar on Eliminating Tobacco Use Faster) (18). Of particular importance is the regulation of additional tobacco products by the FDA.Other healthy approaches to living that can significantly reduce cancer risk are maintaining a healthy weight, which is defined as a body mass index (BMI) between 18.5 and 24.9 kg/m2 for adults over 20 years of age; keeping active; and eating a balanced diet (see sidebar on Reasons to Maintain a Healthy Weight and Keep Active). The impact of adopting these aspects of a healthy lifestyle could be enormous because it is estimated that one-third of all new cancer diagnoses in the United States are related to being overweight or obese, not getting enough physical activity, and/or having poor dietary habits (10, 16). Moreover, more than one-third of adults, or more than 72 million individuals, and 17 percent of youth in the United States are obese (21, 22).Fortunately, regular physical activity, independent of body fatness, can decrease the risk of developing certain cancers (23). However, nearly half of adults in the United States do not meet the recommended guidelines for aerobic physical activity (25) (see sidebar on Physical Activity Guidelines). Moreover, sedentary behavior, independent of body mass and periodic physical activity, can increase the risk of developing certain types of cancer (24).
Beyond preventing the development of some cancers, following these recommendations may also improve outcomes for individuals diagnosed with certain types of cancer, in particular breast, colorectal, and prostate cancers, reducing risk of disease recurrence and metastasis and increasing chance of long-term survival (27-29).
Although small improvements in maintaining a healthy weight and increasing physical activity have been made, more action is urgently needed. Concerted efforts by individuals, families, communities, schools, workplaces and institutions, health care professionals, media, industry, government, and multinational bodies are required to develop effective and comprehensive strategies to promote the maintenance of a healthy weight and the participation in regular physical exercise. One new strategy, Park Rx, an initiative of the National Park Service seeks to encourage health care providers to help patients establish an exercise routine by effectively using their neighborhood parks.
Another way that individuals can reduce their risk of developing cancer, specifically the three main types of skin cancer—basal cell carcinoma, squamous cell carcinoma, and melanoma—is by limiting their exposure to ultraviolet (UV) radiation (see sidebar on Reasons to Protect Your Skin). In fact, the International Agency for Research on Cancer (IARC), an affiliate of the World Health Organization, considers exposure to UV radiation from any source as “carcinogenic to humans” (30), alongside agents such as plutonium and cigarettes.
Despite this, half of all adults in the United States report at least one sunburn in the past 12 months and 5 percent report using a UV indoor tanning device at least once, with many using these devices 10 or more times a year (37, 38). Moreover, 13 percent of all high school students and 21 percent of high school girls report using an indoor UV tanning device in the past year (39).Given that many cases of skin cancer are preventable, it is important that everyone work together to develop and implement more effective policy changes and public education campaigns to help reduce the health and economic burdens of the disease. For example, initiatives aimed at increasing the number of individuals who adopt sun-safe habits and tighter regulation of indoor tanning would dramatically reduce the incidence of skin cancer (see sidebar on Sun-safe Habits).
Persistent infection with a number of pathogens—bacteria, viruses, or parasites that cause disease—can result in certain types of cancer (40, 41) (see Table 4). In fact, pathogens are estimated to cause about 2 million cancer cases each year, with more than 90 percent of these cases attributable to just four pathogens—Helicobacter pylori, hepatitis B virus (HBV), hepatitis C virus (HCV), and human papilloma virus (HPV) (42) (see Figure 7).This knowledge has enabled the development of strategies to eliminate or prevent infection with these cancer-associated pathogens (see sidebar on Cancer-causing Pathogens: Prevention and Elimination). Consulting with a physician and following his or her advice regarding the use of these strategies can reduce an individual’s risk of certain cancers and is part of a healthy approach to living.
Despite the availability of strategies to eliminate or prevent infection with some cancer-associated pathogens, researchers estimate that pathogen-related cancers account for about 20 percent of cancer diagnoses worldwide (40) (see Figure 7). Thus, it is clear that these strategies are not being used optimally and that a dramatic reduction in the global cancer incidence could be achieved by more effective implementation. In fact, the CDC estimates that in 2012, only 33 percent of girls ages 13–17 in the United States had received the recommended three doses of HPV vaccine (60). Moreover, this percentage varies widely among states, with fewer than 26 percent of girls completing the vaccine course in six states, and the lowest rate being just 12.1 percent (44). Further, the “President’s Cancer Panel 2012–2013 Report” stated that in the United States alone, more than 50,000 cases of cervical cancer and thousands of cases of other types of cancer could be prevented if 80 percent of those for whom the HPV vaccine is recommended—girls and boys ages 11 and 12, respectively—were to be vaccinated (44) (see sidebar on The “President’s Cancer Panel Report”).
Research has provided and continues to increase our knowledge of the causes of cancer and the timing, sequence, and frequency of the genetic, molecular, and cellular changes that drive cancer initiation and development. This knowledge provides us with unique opportunities for developing ways to prevent cancer onset or to detect a cancer and intervene earlier in its progression. Finding a cancer early, asCongressman Ron Barber did in 2012, before it has spread to other parts of the body, makes it more likely that a patient can be treated successfully. Cancer screening is therefore an important part of a healthy lifestyle.
Screening to detect cancer in individuals showing no signs or symptoms of the disease they are being screened for can have tremendous benefits (see sidebar on Cancer Screening). However, it can also cause unintended harm, and this has made it difficult to develop strategies for screening for the majority of cancer types. For a screening program to be successful, it must meet two important criteria: It must decrease deaths from the screened cancer, and the benefits it provides must outweigh any harms. Determining whether a screening program meets these criteria requires an enormous amount of research and careful analysis of the data generated.
In the United States, an independent group of experts convened by the Public Health Service rigorously evaluates clinical research to make evidence-based recommendations about clinical preventive services, including cancer-screening tests. These experts form the U.S. Preventive Services Task Force (USPSTF). As of Aug. 1, 2014, the USPSTF recommended that certain segments of the general population be screened for just four types of cancer (see sidebar onUSPSTF Cancer-screening Recommendations). In addition to considering evidence regarding potential new screening programs, the USPSTF routinely evaluates new research regarding established screening programs, and can revise recommendations if deemed necessary.
Although cancer screening is part of a healthy approach to living, it can be difficult for individuals to ascertain which cancers to be screened for and when. The USPSTF and other relevant professional societies’ recommendations are evidence-based guidelines that can help, but they are only one factor to consider when making decisions about cancer screening.
People have their own unique risks for developing each type of cancer. These risks are determined by genetic, molecular, cellular, and tissue makeup, as well as by lifetime exposures to the large number of factors that can increase the risk of developing cancer (see Figure 4). As a result, each individual should consult with his or her physicians to develop a personalized cancer-screening plan that takes into account evidence-based recommendations; the individual’s own cancer risks, including family history; and the individual’s tolerance to specific benefits and harms of screening (see sidebar on Cancer Screening). Importantly, the risk for different types of cancer can vary over time—for example, risk for most cancers increases with age—so it is important that individuals continually evaluate, and update if necessary, their personalized cancer-screening plans.
Some generally healthy individuals are at increased risk of certain cancers because they inherited a cancer-predisposing genetic mutation (see sidebar on How Do I Know If I Am at High Risk for Developing an Inherited Cancer?). However, inheriting a cancer-predisposing genetic mutation is a relatively rare occurrence. In fact, only about 5 percent of all new cases of cancer diagnosed in the United States each year are caused by such mutations (63). To date, not all potentially inheritable causes of cancer have been identified, but if an individual suspects that a relative has a cancer caused by one of the 17 known cancer-predisposing genetic mutations (see Table 5), he or she should consult a physician and consider genetic testing for verification.
As part of a healthy approach to living, persons who are at risk for developing an inherited cancer—both those who learn they carry a known cancer-predisposing genetic mutation and those who fulfill criteria for being at risk—should consult with their doctors to determine how this influences their personalized cancer prevention and screening plans. Some patients may be able to reduce their risk of developing cancer by modifying their behaviors. Others might need to increase their participation in screening or early detection programs or even consider taking a preventive medicine or having risk-reducing surgery (see Tables 6 and 7).
Beyond inherited cancers, a number of medical conditions place an individual at higher risk for certain types of cancer. For example, ulcerative colitis and Crohn disease increase an individual’s risk for colorectal cancer sixfold, but they are relatively rare conditions (64). A far more prevalent medical condition that increases an individual’s risk for developing cancer is type 2 diabetes, which raises the risk of developing liver, pancreatic, and endometrial cancers (65, 66). These factors are important considerations when developing a personalized cancer prevention and screening plan.
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