By Martin Lipsky, MD

Chancellor, South Jordan Campus, Roseman University of Health Sciences, South Jordan, UT

Dr. Lipsky reports no financial relationships relevant to this field of study.

SYNOPSIS: A healthy lifestyle may substantially reduce the burden of cancer.

SOURCE: Song M, Giovannucci E. Preventable incidence and mortality of carcinoma associated with lifestyle factors among white adults in the United States. JAMA Oncol 2016 May 19. doi: 10.1001/jamaoncol.2016.0843. [Epub ahead of print].

Cancer remains the second leading cause of death in the United States, with 1.6 million new cancers and 600,000 deaths projected for 2016.1 Although the annual adjusted death rate continues declining, the reduction in cancer deaths is modest when compared to deaths from cardiovascular disease. One explanation for this slower decline comes from a recent study that suggested the number of lifetime cell divisions correlates with the lifetime risk of cancer.2 This study led some experts to conclude that only one-third of cancer risk is attributable to environmental factors and that cancer mutations may be more closely related to so-called bad luck. To shed more light on the role of environmental factors, Song and Giovannucci estimated the contribution of common lifestyle factors to cancer risk and the effect of lifestyle modification on preventing cases and deaths from carcinoma.

The authors used four criteria to define a healthy lifestyle: never smoking or quit smoking; drinking either no alcohol or a maximum of one drink a day for women and two or less for men; a body mass index (BMI) of > 18.5 kg/m2 but < 27.5 kg/m2; and weekly aerobic exercise, either 150 minutes of moderately intense activity or 75 minutes of vigorous activity. The study population included those enrolled in the Nurses’ Health Study (NHS) and the Health Professionals Follow-Up Study. Individuals meeting all lifestyle criteria were considered low risk, while those who did not were defined as high risk. The authors calculated the population-attributable risk (PAR) by comparing incidence and mortality of total and major individual carcinomas between the low- and high-risk groups. The researchers further assessed the PAR by comparing the low-risk group to the U.S. population.

The total study group included 89,571 women and 46,339 men from the two cohorts, with 16,531 and 11,731 men assigned to the low-risk group. Within the two cohorts, investigators found that between 20-40% of cancer cases and about 50% of cancer deaths possibly could be prevented if individuals adopted the low-risk group lifestyle. The study also examined specific cancers and found the PAR varied by cancer type in the prospective cohorts from a high of 82% for lung cancer risk in women (78% in men) to lows of 4% for breast cancer and 21% each for endometrial, ovarian, and fatal prostate cancers. The PARs were substantially higher when comparing the health lifestyle group to the U.S. population, ranging from a high of 85% for lung cancer risk in women to a low of 15% for breast cancer.3

The authors concluded that a substantial cancer burden may be prevented through lifestyle modification, and that primary prevention should remain a priority for cancer control.

COMMENTARY

The study findings certainly should resonate with primary care physicians, adding to the large body of evidence supporting the benefits of a healthy lifestyle. Although the link between lifestyle and cardiovascular disease is well recognized, the connection between cancer and lifestyle may be less appreciated. In terms of return on investment, a healthy lifestyle and primary prevention trump cancer screening strategies that often seem to be more fully embraced by the public and providers. Song and Giovannucci believe their findings reinforce the importance of lifestyle in determining cancer risk and the value of primary prevention strategies.3 As Colditz and Sutliffe succinctly noted in an accompanying editorial, cancer is not inevitable but should be viewed as a potentially preventable disease.4 They recommend an array of interventions targeting individuals, clinicians, communities, and society.3

Unfortunately for clinicians who embrace primary prevention, there is often little reward or time to support their efforts to counsel patients and families about lifestyle. Although research supports the benefit of counseling, it remains challenging for physicians to find the time to adequately counsel individuals and families in a healthcare environment that may allow only 15 minutes per patient visit. The findings of this study should serve to help both motivate individuals and clinicians to address primary prevention and policy to support these activities from the reimbursement perspective. While no one should ignore the importance of new medical discoveries in cancer treatment and diagnosis, the new moonshot proposal to cure cancer should not overlook the value of prevention in reducing the morbidity and mortality of this dreadful disease.5

REFERENCES

  1. Siegel RL, Miller KD, Jenner A. Cancer statistics 2016. CA Cancer J Clin 2016;66:7-30.
  2. Tomasetti C, Vogelstein B. Cancer etiology: Variations in cancer risk among tissues can be explained by the number of stem cell divisions. Science 2015;347:78-81.
  3. Song M, Giovannucci E. Preventable incidence and mortality of carcinoma associated with lifestyle factors among white adults in the United States. JAMA Oncol 2016 May 19. doi: 10.1001/jamaoncol.2016.0843. [Epub ahead of print].
  4. Colditz GA, Sutliffe S. The preventability of cancer: Stacking the deck. JAMA Oncol Published online May 19, 2016. doi:10.1001/jamaoncol.2016.0889.
  5. McCarthy M. US president endorses “moonshot” effort to cure cancer. BMJ 2016;353:213.