Role of Lifestyle in Cancer Development

Dr. Poorvi Desai
Dr. Poorvi Desai MD, and Amy         Comander, MD

Article Highlights

  • At least 42% of newly diagnosed cancers in the United States are potentially avoidable because they are attributable to lifestyle factors such as smoking, alcohol consumption, poor nutrition, and lack of physical activity.
  • Despite the growing body of evidence favoring health promotion in cancer care, there are a number of barriers to implementation including lack of clinician education on these topics, lack of clinician time, and lack of appropriate referrals.
  • Several organizations, including ASCO, have outlined guidelines for addressing lifestyle interventions to mitigate barriers in health promotion in cancer care.

Because of advances in treatment and early detection, as well as the growth and aging of the population, the number of cancer survivors living in the United States continues to increase each year.1 In 2019, more than 16.9 million people with a history of invasive cancer were alive in the United States. By 2030, the number of cancer survivors is projected to increase to 22 million. Although the survival rates for many cancers have improved, risk factors for cancer development are becoming more prevalent. Currently, 41% of men and 39% of women will develop cancer during their lifetime.1 According to the American Cancer Society (ACS), excluding non-melanoma skin cancer, at least 42% of newly diagnosed cancers in the United States are potentially avoidable because they are attributable to lifestyle factors.1 Specifically, 19% of newly diagnosed cancers may be due to smoking, and 18% to a combination of excess body weight, excessive alcohol consumption, poor nutrition, and lack of physical activity.1 There exists a need to focus on health promotion as a key component of cancer risk reduction, as well as in survivorship care. However, the care for cancer survivors is fragmented and can be an afterthought upon completion of active treatment.2 Oncologists should be aware that there are robust evidence-based guidelines to help facilitate lifestyle modifications in cancer care.


Dr. Amy Comander

The increasing prevalence of obesity has troubling consequences in terms of cancer risk and outcomes for specific types of cancer. The 2020 Annual Report to the Nation on the Status of Cancer states that excess body weight (body mass index, or BMI > 25 kg/m2) is associated with at least 13 different types of cancer, including colon, rectal, and postmenopausal breast cancer.3 Obesity (BMI > 30 kg/m2) is also correlated with poorer survival among patients with breast, prostate, and colorectal cancers. In contrast, tobacco use has been linked to at least 12 different cancers, and alcohol use

to at least six. Today more than two-thirds of Americans are overweight or obese, and prevalence is increasing each year, with substantial disparities by race, ethnicity, and socioeconomic status. It is thought that the effect of the current obesity epidemic could potentially halt or reverse the progress achieved in cancer incidence and mortality reduction.4

The increasing prevalence of obesity has troubling consequences in terms of cancer risk and outcomes for specific types of cancer.

In 2017, a study using Surveillance, Epidemiology, and End Results data reported that the risk of noncancer deaths among patients who have ever had cancer now surpasses that of cancer deaths.5 It is important to recognize that noncancer deaths primarily occur for one of two reasons: (1) acute, iatrogenic, or treatment-induced infections; or (2) chronic, comorbid conditions, which are most commonly secondary to cardiovascular and cerebrovascular complications.5 Increased risk of cardiovascular toxicities can be due to cancer treatment, lifestyle, or a combination of both. Accelerated aging (telomere shortening, decreases in maximal oxygen consumption, and increased levels of inflammatory cytokines) is evident in cancer survivors, and this may manifest as cardiac toxicities, sarcopenia, and osteoporosis.2 Thus, there is a need to focus on health promotion for both cancer prevention and survivorship purposes.

Barriers to Health Promotion in Cancer Care

Clinicians need education on weight management strategies

Despite the growing body of evidence favoring health promotion in cancer care, there are a number of barriers to implementation. In 2019, the Obesity and Energy Balance Subcommittee of the ASCO Cancer Prevention Committee surveyed 971 oncologists regarding their attitudes and practice of addressing diet, physical activity, and weight management in patients with cancer.6 The majority of respondents indicated a belief that the evidence linking obesity to cancer outcomes was strong, and that weight and related factors should be addressed as part of cancer treatment. However, referrals to providers and programs to support lifestyle factors occurred less frequently. A number of barriers were identified to explain this, including oncologists’ lack of education on these topics, lack of time, and lack of appropriate referrals to weight management and physical activity programs.

Table. American Cancer Society Guidelines on Diet and Physical Activity for Cancer Prevention13

An ASCO initiative on obesity and cancer emerged to help address this concern.7 ASCO has identified a number of resources available to oncology providers, including guides that illustrate the impact of obesity on treatment, weight management strategies and implementation, clinical practice guidelines, and coverage and reimbursement. There are also resources for cancer survivors, with information about weight-loss strategies, including dietary factors, the role of weight-loss medication and surgery, and how to identify community resources. ASCO endorses the American Board of Obesity Medicine for providers to learn about the treatment of obesity and enroll in CME events. The initiative further brings together several organizations including the Academy of Nutrition and Dietetics, the American College of Sports Medicine (ACSM), and the American Society for Metabolic and Bariatric Surgery to increase awareness of the impact of obesity on cancer and to promote further research in this area.8

Clinicians must encourage physical activity during cancer treatment

Physical activity is also an important area for cancer risk reduction and for cancer survivorship. Physical activity is beneficial for reducing risk of several types of cancer, including breast, colon, endometrial, kidney, bladder, esophageal, and stomach. Minimizing time spent in sedentary behavior may also lower risk of endometrial, colon, and lung cancers.9 It was previously thought that patients with a diagnosis of cancer should not engage in exercise or strenuous activity. More recent studies show that in fact, the opposite is true, and physical activity should be encouraged, as it is generally safe and well tolerated.10 Furthermore, physical activity improves health-related quality of life and fitness among cancer survivors, and has been shown to improve survival rates among breast, colon, and prostate cancer survivors. The ACSM recommends a goal of 150 to 300 minutes of moderate aerobic exercise, or 75 to 100 minutes of vigorous aerobic exercise, per week, along with resistance training two to three times per week. There is strong evidence that physical activity also improves cancer-related fatigue, health-related quality of life, physical function, anxiety, and depression (Fig. 1).11 At The University of Texas MD Anderson Cancer Center, Amy Ng, MD, MPH, and colleagues recently surveyed 200 adult cancer survivors and found that only 34% were adhering to the recommended exercise duration.12 The main barriers to adherence were reported as issues of motivation, including lack of interest and self-discipline, and symptoms of pain and fatigue.

Fig 1. ACSM Guidelines for Exercise and Cancer11

American College of Sports Medicine cine®

Resources for Lifestyle Interventions

In addition to ASCO, several other organizations have outlined guidelines for addressing lifestyle interventions to mitigate these barriers. Excellent resources include guidelines from the World Cancer Research Fund and American Institute for Cancer Research (WCRF/AICR); a role-playing training simulation from the ACS called “Let’s Talk: Nutrition, Physical Therapy and Cancer Survivorship”; the ACSM Moving Through Cancer exercise program registry; and the National Comprehensive Cancer Network (NCCN) Survivorship Panel on Healthy Lifestyles. The WCRF/AICR has been at the forefront of synthesizing, interpreting, and evaluating the accumulated evidence on the relationship between cancer risk and diet, nutrition, physical activity, and weight for more than 3 decades. In 2020, ACS published guidelines for diet and physical activity for cancer risk reduction that are based largely on WCRF/AICR systematic reviews, as well as on the ACSM consensus.13 These guidelines provide four recommendations for individuals: (1) achieve and maintain a healthy body weight throughout life; (2) be physically active; (3) follow a healthy eating pattern; and 4) avoid alcohol (Table).13 The AICR also specifies 10 recommendations for cancer risk reduction (Fig. 2).14 The same guidelines apply in cancer survivorship. The ACSM Moving Through Cancer initiative has developed a searchable registry to help healthcare providers and patients find appropriately trained professionals and programs throughout their community, including links to find ACSM/ACS Certified Cancer Exercise Trainers.15 The ACS Comprehensive Cancer Control initiative launched “Let’s Talk” to train health care providers in how to use evidence-based strategies for conversations about weight, diet, and activity; how to incorporate referrals to exercise trainers and registered dietitians; and how to provide other resources for lifestyle change while keeping in mind that the role of the health care provider is ideally one of guidance and delegation rather than in-depth counseling.16

The NCCN Guidelines for Survivorship encourage preventative health, including promotion of healthy lifestyle behaviors. These guidelines take specific cancer subtypes into consideration for highest risk of disease and treatment toxicities.17 In general, in terms of dietary recommendations, the guidelines emphasize the importance of an unprocessed, plant-based dietary pattern, in line with ACS recommendations. Oncologists should collaborate with other providers to ensure patients maintain a normal BMI while also assessing metabolic health and body composition independently of BMI. Vitamin deficiencies should be screened for at routine intervals, and patients should be regularly asked about supplement use. Supplements are not recommended for most survivors unless required by documented deficiencies, an inadequate diet, or comorbid conditions. Cancer survivors should be encouraged to obtain nutrients from dietary intake.

Fig 2. American Institute for Cancer Research Ten Recommendations for Cancer Prevention14

Empowering cancer survivors to adopt healthy lifestyle behaviors also requires tremendous behavior change support and comprehensive psychosocial evaluation. Cancer survivors face many psychosocial consequences of treatment, including distress, depression, and anxiety, fear of recurrence, concerns about returning to work, and financial issues.2 Sleep disorders and insomnia are prevalent and known to last well into the long-term survivorship phase of cancer. Distress screening should occur at each visit, with referrals to readily available mental health professionals for assessment and triage. The NCCN Survivorship resources provide a distress assessment thermometer along with management guidelines to address psychosocial and physical problems.17

Empowering cancer survivors to adopt healthy lifestyle behaviors also requires tremendous behavior change support and comprehensive psychosocial evaluation.

It is understandably a challenge to help cancer survivors make lifestyle changes. Oncology providers are not expected to have the expertise to provide these services themselves; instead, these interventions require a team approach, ideally with other physicians, nutritionists, exercise trainers, social workers, and psychologists, as well as access to weight management and tobacco cessation programs. There are several helpful tools available to oncology practices. Taken together, the focus on lifestyle should be emphasized for cancer risk reduction at any stage of cancer care, including during active treatment and beyond.