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A Step in the Maturation of the Field of Lifestyle Change Interventions

University of California, Los Angeles, Jonsson Comprehensive Cancer Center, Los Angeles, CA

The report by Vallance et al¹ in this issue represents another important step in the maturation of the field of lifestyle change interventions applied to cancer survivors. If oncologist attitudes are an indication, there is already a consensus that exercise is beneficial (62.0%), important (55.8%), and safe (63.1%) for patients with cancer during treatment.² Despite these positive attitudes, only 28% of oncologists had recommended exercise to their patients in the last month. The field must continue to mature in terms of its scientific sophistication and credibility of its conclusions to justify to policy makers the expenditure of resources necessary to make exercise central to the rehabilitation of the cancer patient, as it is has been for two decades to the rehabilitation of the older coronary heart disease patient.³

The report by Vallance et al¹ addresses some of the weaknesses noted in reviews of the literature evaluating the impact of physical activity interventions on breast cancer survivor outcomes. However, further maturation of the field will require more attention to causal mechanisms and mediational pathways, to issues involving adherence to the prescribed lifestyle changes, to identifying more cost-effective ways to expose patients to the physical activity prescription, and to tailoring type, frequency, duration, and intensity of physical activity prescription to the specific needs of patients.

CAUSAL MECHANISMS AND MEDIATIONAL PATHWAYS

What are the mechanisms by which regular moderate and/or vigorous physical activity would be expected to influence quality of life and longevity in breast cancer survivors? Friedenreich and Orenstein⁴ enumerated several possible mechanisms, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity, and, possibly, changes in immune function. In the study by Vallance et al,¹ a somewhat obvious potential influence on trial participation and adherence to the exercise prescription was ignored, namely, normative beliefs in the healthfulness of physical activity. Vallance et al¹ did not comment on their unexpected great success in recruiting patients onto their trial; they enrolled 377 participants instead of the 252 for which they had originally planned. The positive beliefs about physical activity held by family members and friends may have contributed to both the unexpectedly great recruitment success and the high follow-up rates of adherence to the exercise prescription. Whether these normative beliefs moderated or mediated the impact of exercise prescription on subsequent quality of life is a matter that could be resolved empirically. This is just one of the many questions about possible mechanisms that future research will need to resolve to improve understanding of the ways in which individuals can sustain healthier long-term lifestyle choices. Possible causal mechanisms, such as those enumerated above, cannot be tested without greater investment of research resources into laboratory assays such as double-labeled water studies, assessment of changes in high-density lipoprotein cholesterol/serum triglycerides or changes in insulin resistance, and appropriately trained personnel to collect these additional measures.

ISSUES INVOLVING ADHERENCE

The biggest challenge in encouraging health-related lifestyle change in patients is not the initial change but rather their ability to adhere to a long-term change. Vallance et al¹ finessed this challenge by measuring adherence relatively soon after the end of the intervention. A better measure of long-term adherence to voluntary health-related lifestyle change is a follow-up assessment at least 1 year after the beginning of the intervention. Adherence to ambitious behavior changes such as smoking cessation and regular physical activity can be remarkably high in cardiac rehabilitation patients (with rates of 50% or more who adhered at 5-year follow-up), despite the fact that the impetus for the change came from a sudden cardiac event and thus allowed for little planning and that changes were required simultaneously in tobacco use, physical activity, and dietary choices.⁵ Long-term adherence to physical activity recommendations is usually much less.⁶ Without more research on effective ways to help cancer survivors sustain recommended levels of physical activity, the rates of adherence by cancer survivors to federally recommended physical activity changes are likely to remain low (approximately 30%).⁷ Longer term assessments cost money, of course, and therefore, research in this field has tended to be limited to short-term (< 1 year) follow-up assessments.

IDENTIFYING MORE COST-EFFECTIVE WAYS TO EXPOSE CANCER PATIENTS TO THE PHYSICAL ACTIVITY PRESCRIPTION

Tobacco control, because of its longer history of research support, currently serves as a model for health-related lifestyle change efforts involving physical activity and dietary choices.⁸ Cost-effective strategies have emerged from years of trying a variety of intervention strategies that use the clinician as the starting point for the desired behavior change but rely on allied health professionals to provide the intensive behavioral counseling.⁹ Vallance et al¹ were explicit in citing cost as a reason to try clinic-based versus distance-based approaches to encouraging patients to adhere to recommended physical activity levels. Clinician encouragement coupled with telephone counseling may be the best marriage of both clinic-based and distance-based approaches, and this combination has proved to be useful in tobacco control.¹⁰

TAILORING TYPE, DURATION, FREQUENCY, AND INTENSITY OF PHYSICAL ACTIVITY PRESCRIPTION TO THE SPECIFIC NEEDS OF PATIENTS

Although walking is the older person's favored means of physical activity,¹¹ a significant minority prefer other forms of activity such as swimming and cycling. Moreover, there is a case for advocating cross training (switching regularly between forms of activity) because cross training reduces overuse injuries and promotes better long-term adherence to daily physical activity by reducing any risk of boredom.¹² More research is needed to optimize the match between intervention characteristics and patient needs.

Fortunately, the continuing maturation of the field, coupled with the steady accumulation of positive results, provides increasing leverage with which to solicit additional investment in the field. As exemplified by Vallance et al,¹ continued maturation of the field of health-related lifestyle change in cancer survivors will provide important new knowledge that clinicians can use to benefit their patients, if society invests the appropriately increased resources needed to make such research possible.

AUTHOR'S DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

The author(s) indicated no potential conflicts of interest.

REFERENCES

1. Vallance JKH, Courneya KS, Plotnikoff RC, et al: A randomized controlled trial of the effects of print materials and step pedometers on physical activity and quality of life in breast cancer survivors. J Clin Oncol 25:2352-2359, 2007[Abstract/Free Full Text]

2. Jones LW, Courneya KS, Peddle C, et al: Oncologists' opinions towards recommending exercise to patients with cancer: A Canadian national survey. Support Care Cancer 13:929-937, 2005[CrossRef][Medline]

3. Williams MA, Fleg JL, Ades PA, et al: Secondary prevention of coronary heart disease in the elderly (with emphasis on patients 75 years of age): An American Heart Association scientific statement from the Council on Clinical Cardiology Subcommittee on Exercise, Cardiac Rehabilitation, and Prevention. Circulation 105:1735-1743, 2002[Free Full Text]

4. Friedenreich CM, Orenstein MR: Physical activity and cancer prevention: Etiologic evidence and biological mechanisms. J Nutr 132:3456S-3464S, 2002 (suppl)[Abstract/Free Full Text]

5. Alderman EL, Andrews K, Brooks MM, et al: Five-year clinical and functional outcome comparing bypass surgery and angioplasty in patients with multivessel coronary disease: A multicenter randomized trial. JAMA 277:715-721, 1997[Abstract]

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7. Bellizzi KM, Rowland JH, Jeffery DD, et al: Health behaviors of cancer survivors: Examining opportunities for cancer control intervention. J Clin Oncol 23:8884-8893, 2005[Abstract/Free Full Text]

8. Mercer SL, Green LW, Rosenthal AC, et al: Possible lessons from the tobacco experience for obesity control. Am J Clin Nutr 77:1073S-1082S, 2003 (suppl)[Abstract/Free Full Text]

9. Whitlock EP, Orleans CT, Pender N, et al: Evaluating primary care behavioral counseling interventions: An evidence-based approach. Am J Prev Med 22:267-284, 2002[CrossRef][Medline]

10. Lichtenstein E, Glasgow RE, Lando HA, et al: Telephone counseling for smoking cessation: Rationales and meta-analytic review of evidence. Health Educ Res 11:243-257, 1996[Abstract/Free Full Text]

11. Booth ML, Bauman A, Owen N, et al: Physical activity preferences, preferred sources of assistance, and perceived barriers to increased activity among physically inactive Australians. Prev Med 26:131-137, 1997[CrossRef][Medline]

12. Godfrey RJ: Cross-training. Sports Exerc Inj 4:50-55, 1998

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