Primary and secondary prevention of colorectal cancer: An evidencebased review

Sandra J. Gonzalez, Maria C. Mejia de Grubb, Robert S. Levine

Primary and secondary prevention of colorectal cancer: An evidencebased review

Sandra J. Gonzalez1, Maria C. Mejia de Grubb1, Robert S. Levine1

Colorectal cancer (CRC) is a common cancer that affects one in three men and one in four women worldwide. Late-stage detection is associated with significantly lower 5-year survival rates.Although it is well established that CRC mortality rates have decreased in the past several decades,adoption of routine screening continues to lag behind screening for other common cancers such as cervical and breast cancer. The decrease in overall rates has been attributed, in part, to improved primary and secondary prevention efforts, including smoking prevention and cessation programs,nutritional counseling, and the use of evidence-based screening protocols, as well as access to better treatment. Despite the increased screening rates, it is estimated that at least one-third of eligible people do not receive appropriate screening. The objective of this review is to describe the current epidemiology of CRC and to demonstrate effective primary and secondary prevention strategies for the primary care provider.

Colorectal cancer; adenocarcinoma; modifi able risk factors; primary prevention;secondary prevention; primary care

Introduction

Colorectal cancer (CRC) is the third most commonly diagnosed type of cancer in men and women [1]. The American Cancer Society forecast for 2017 is for 95,520 new cases of colon cancer and 39,910 new cases of rectal cancer in the United States. Although CRC morbidity and mortality rates in the United States have been steadily declining in the past 20 years, the rates remain high relative to those in many other industrial nations [1].There are a number of risk factors that have been associated with CRC, including inactivity, obesity/overweight, nutrition, smoking,and excessive alcohol consumption [2]. The decrease in overall rates has been attributed,in part, to improved primary and secondary prevention efforts, including smoking prevention and cessation programs, nutritional counseling, and the use of routine screening tests, as well as access to better treatment(tertiary prevention) [3]. Primary and secondary prevention strategies can be used by primary care providers to reduce the rate at which new disease occurs as well as disease burden as ref l ected in morbidity, mortality,fi nancial costs, and diminished quality of life.

Epidemiology

In 2012 there were nearly 1.4 million new CRC cases worldwide [4, 5]. CRC is the third most common cancer in men(746,000 cases, 10.0% of the total) and the second in women(614,000 cases, 9.2% of the total) [5]. In the United States the highest rates of diagnosis were in people aged 65—84 years,with a greater incidence and disproportionately high mortality rate in black males and females [1]. In addition, incidence rates differ tenfold in both sexes worldwide, with almost 55%of new cases arising in more developed countries. The highest incidence rates are found in Australia/New Zealand [agestandardized rates (ASR) 44.8 and 32.2 per 100,000 in men and women respectively], and the lowest are found in western Africa (4.5 and 3.8 per 100,000) [5] (Fig. 1). The vast majority of CRC cases develop in individuals with average risk factors, whereas only about 20% of cases develop in people who have a family history [1]. Nonetheless, the lifetime risk of developing CRC is two to three times higher in people with a fi rst-degree relative who has colon cancer or an adenomatous polyp than in the general population [6]. CRC has been associated with the Western diet and lifestyle factors, which include consumption of foods that are high in red and processed meats and physical inactivity [7].

Fig. 1. Number of cancer cases and deaths worldwide in 2012(in millions).

There were an estimated 694,000 deaths worldwide (8.5%of the total number of cancer deaths, fourth most common cause of cancer-related deaths). Although mortality rates were lower in 2012 (Table 1), disparities persisted, showing more than half of deaths (52%) occurred in the less developed regions of theworld, ref l ecting poorer survival in these regions [5]. In 2012,central and eastern Europe showed the highest estimated mortality rates for both sexes (20.3 per 100,000 for men, 11.7 per 100,000 for women), while western Africa showed the lowest(3.5 per 100,000 for men and 3.0 per 100,000 for women). The 5-year prevalence of CRC (i.e. the number of CRC patients who were still alive 5 years after diagnosis) was estimated at 3,543,582 worldwide (68.2 CRC survivors per 100,000 population), and the cumulative risk of CRC in individuals younger than 75 years was 1.95% worldwide (2.36% in men, 1.57% in women) [5] (Table 1).

Table 1. Epidemiology of colorectal cancer worldwide

Primary prevention of CRC

Much of primary cancer prevention is designed to avert cancer by living a healthy lifestyle and avoiding cancer-causing substances, such as tobacco. Although the benefi t of screening (secondary prevention) is clear, there is also extensive evidence to support the impact of primary prevention activities,primarily through lifestyle modification. The annual report to the nation on the status of cancer estimated that increased screening in combination with a significant but achievable reduction in lifestyle risk factor prevalence from the rates in 2000 could reduce CRC mortality by as much as 50% in 2020[9]. Compelling evidence indicates that avoidance of smoking and heavy alcohol consumption, prevention of weight gain, and the maintenance of a reasonable level of physical activity are associated with markedly lower risks of CRC [10].Modifying lifestyle risk factors such as obesity [11], high red meat consumption [12], cigarette smoking [13, 14], and alcohol abuse [15] have been associated with a decreased risk of CRC development [10, 16]. Thus to achieve a meaningful reduction in CRC incidence, primary prevention is an essential complement to CRC screening and early intervention [17] (Fig. 2).Data suggest that cessation of smoking late in life does not necessarily eliminate the increased risk of CRC; it is critical to prevent smoking in adolescents and young adults and to convince smokers to quit as early as possible [10]. Smokers have an approximately twofold increased risk of receiving a diagnosis of an adenoma and higher risk of CRC-related death associated with current smoking [14]. In addition to lifestyle modification, it is also important to note that colonoscopy,while generally considered as part of screening (or secondary prevention), may also play a part in primary prevention since removal of noncancerous polyps from the colon may prevent CRC from starting in the fi rst place [18].

Fig. 2. Age-specific incidence of colon cancer per 100,000 personyears from age 30 years to age 70 years, according to screening behavior, for 1) a “high-risk” participant (one who accrued 10 packyears, of smoking before age 30 years, had a consistently high relative body weight, had physical activity of 2 metabolic equivalent (MET)-hours/week, consumed 1 serving of red or processed meat per day,was never screened for colon cancer, and had a folate intake of 150μg/day); 2) a “high-risk” participant who was screened from age 50 years to 70 years; 3) a “moderate-risk” participant (one who was a nonsmoker, had an average body mass index, had physical activity of 13.5 MET-hours/week, did not consume red or processed meat, was never screened, and had a folate intake of 300 mg/day); and 4) a “l(fā)owrisk” participant (one who was a nonsmoker, had a consistently low relative body weight, had physical activity of 21 MET-hours/week,did not consume red or processed meat, was never screened, and had a folate intake of 400 μg/day), Nurses’ Health Study, 1980—2004.

Secondary prevention and screening for early detection of CRC

Factors such as obesity, nutrition, and smoking are most closely associated with the primary prevention of ascending colon cancer [19]. Secondary prevention, in the form of CRC screening, is most closely associated with successful descending colon cancer and CRC prevention [19].So any comprehensive CRC prevention program must also incorporate CRC screening, a service whose ‘A’ rating from the US Preventive Services Task Force on a regular basis for people aged 50—75 years and on an individual basis for people aged 76—85 years was reiterated in June 2016. The US Preventive Services Task Force also recognized a number of critical barriers to screening, which is recognized as a widely underused service: “Screening is a cascade of activities that must occur in concert, cohesively, and in an organized way for benefi ts to be realized, from the point of the initial screening examination (including related interventions or services that are required for successful administration of the screening test, such as bowel preparation or sedation with endoscopy) to the timely receipt of any necessary diagnostic follow-up and treatment ”[20]. At the same time, the US Preventive Services Task Force addressed a variety of screening strategies in its recommendation and stated that“there are no empirical data to demonstrate that any of the reviewed strategies provide a greater net benefi t” [21] (Table 2). A number of evidence-based strategies have also been recognized by the Community Preventive Services Task Force, including clinician and patient reminder systems, use of small media (e.g. videos, letters, and brochures), reduction of structural barriers to screening (e.g. time or distance to screening setting or offering extended or nonstandard clinic hours), and provision of clinician assessment and feedback about screening rates [20]. There is also evidence that patient navigators increase screening rates, decrease no-show rates,and improve patients’ preparation for screening tests [22].

Current cancer screening rates are particularly disappointing among ethnic minorities and individuals with low socioeconomic status, who often present with late-stage diagnoses and have high mortality rates [23]. Decreases in CRC rates are attributed to improved screening, removal of precancerous lesions, and reduction in modifi able risk factors such as smoking and excessive alcohol consumption [4]. Despite these decreases, a recent survey found that only two-thirds of alleligible patients received screening from their health care provider [24]. Although primary care physicians are most likely to deliver preventive services, they are often doing so within systems that are already taxed by time constraints, administrative tasks, and lower reimbursement [25]. A number of effective strategies have been identifi ed to address these challenges,including use of a team-based approach, optimization oh the use of electronic medical records, and creation of patient registries [25, 26]. The concepts are concordant with the patientcentered medical home model of service delivery that has taken hold in many health systems across the United States in the past decade [27]. Using a team-based approach, physicians can work closely with all members of their team to ensure that eligible patients are identifi ed and screened in a timely manner.A pilot study involving seven community-based primary care clinics in Utah found that the use of electronic medical record reminders, provider and medical assistant education on screening, and an expanded role for the medical assistant was associated with an increase in the colonoscopy referral rate from 6.0% at the baseline to 13.4% [28].

Table 2. Effect of screening intervention on reducing mortality from colorectal cancer

Primary care role

Primary care providers have key roles in the prevention,diagnosis, and management of CRC. Previous authors have reinforced the fact that successful screening should start with primary care [29, 30]. A systematic review of strategies for CRC screening at the population level showed higher participation rates with the involvement of a primary care practitioner, a more personalized recruitment approach, and reduction of barriers that discourage participation [31]. However, the increase in CRC screening rates largely depends on implementation of effective systems of decision support (e.g. electronic medical record reminders)and procedures for screening delivery (e.g. registries) in primary care practices. CRC screening recommendations by primary care providers targeting high-risk patients to ensure that they complete their fi rst fecal occult blood test has proven to be effective[32]. A primary care provider’s failure to inform patients of the usefulness and the availability of routine screening tests could result in significant delays in early cancer diagnosis, thus having an important impact on patients’ survival.

Other perspectives

CRC is also an important health problem in countries with a Westernized lifestyle outside the United States. In European countries, for example, CRC mortality has been observed to be much higher than that in the United States, leading, in part,to recommendations for “program screening” (requiring public responsibility by law or official regulation) in addition to screening obtained outside programmatic settings [33]. For public organized programs, it is recommended that there be a regional or national team responsible for implementation,quality, and reporting, and that the screening test, examination interval, and eligible population group are also specifi ed[33]. Screening approaches in these programs have differed according to country. In 2007, for example, guaiac-based fetal occult blood testing was the only screening method in 12 countries, while six countries used two types of test from among both guaiac and immunochemical fetal occult blood testing as well as fl exible sigmoidoscopy. In most countries,colonoscopy is used for follow-up of positive screening test results, but in Poland, colonoscopy was the only method used.Screening intervals also differ widely — anywhere from 1 year to 10 years — with the latter ref l ecting reliance on CRC screening. These variations ref l ect, in part, the evolving nature of knowledge of CRC screening.

Conclusion

CRC risk can be lowered through a comprehensive approach that includes both primary and secondary prevention strategies. Primary care providers are in an ideal position to help patients identify lifestyle risks that may place them at an elevated risk of developing CRC. The use of a team-based approach, which includes physicians, nurse practitioners,physicians’ assistants, nurses, patient navigators, and behaviorists, may alleviate common barriers such as time constraints, and provide patients with more comprehensive,whole-person care [25]. Adoption of evidence-based tobacco and alcohol screening and briefintervention programs can assist primary care providers in identifying individuals at risk [34, 35].

Conflict ofinterest

The authors declare no conflict ofinterest.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profi t sectors.

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1. Department of Family and Community Medicine, Baylor College of Medicine, Houston,TX, USA

Sandra J. Gonzalez, MSSW,LCSW

Department of Family and Community Medicine, Baylor College of Medicine, 3701 Kirby Drive, Houston, TX 77098, USA E-mail: sandra.gonzalez@bcm.edu

31 January 2017;Accepted 16 March 2017