|
|||||
|
|
||||||
Journal of Clinical Oncology, Vol 25, No 17 (June 10), 2007: pp. 2345-2351 © 2007 American Society of Clinical Oncology. DOI: 10.1200/JCO.2006.08.6819 Greater Survival After Breast Cancer in Physically Active Women With High Vegetable-Fruit Intake Regardless of Obesity
From the Moores University of California, San Diego Cancer Center, La Jolla; Stanford Prevention Research Center, Stanford University, Palo Alto; Division of Research, Kaiser Permanente Medical Group Inc, Oakland, CA; Arizona Cancer Center, Tucson, AZ; and The University of Texas M.D. Anderson Cancer Center, Houston, TX Address reprint requests to John P. Pierce, PhD, Cancer Prevention and Control Program, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA 92093-0901; e-mail: jppierce{at}ucsd.edu
Purpose: Single-variable analyses have associated physical activity, diet, and obesity with survival after breast cancer. This report investigates interactions among these variables. Patients and Methods: A prospective study was performed of 1,490 women diagnosed and treated for early-stage breast cancer between 1991 and 2000. Enrollment was an average of 2 years postdiagnosis. Only seven women were lost to follow-up through December 2005. Results: In univariate analysis, reduced mortality was weakly associated with higher vegetable-fruit consumption, increased physical activity, and a body mass index that was neither low weight nor obese. In a multivariate Cox model, only the combination of consuming five or more daily servings of vegetables-fruits, and accumulating 540+ metabolic equivalent tasks-min/wk (equivalent to walking 30 minutes 6 d/wk), was associated with a significant survival advantage (hazard ratio, 0.56; 95% CI, 0.31 to 0.98). The approximate 50% reduction in risk associated with these healthy lifestyle behaviors was observed in both obese and nonobese women, although fewer obese women were physically active with a healthy dietary pattern (16% v 30%). Among those who adhered to this healthy lifestyle, there was no apparent effect of obesity on survival. The effect was stronger in women who had hormone receptorpositive cancers. Conclusion: A minority of breast cancer survivors follow a healthy lifestyle that includes both recommended intakes of vegetables-fruits and moderate levels of physical activity. The strong protective effect observed suggests a need for additional investigation of the effect of the combined influence of diet and physical activity on breast cancer survival.
Dietary pattern and moderate levels of physical activity (PA) have each been linked separately to survival after breast cancer in some1-5 but not all6,7 studies. Given that both diet and PA have each been shown to modify circulating gonadal hormone concentrations,8,9 their effect on survival after breast cancer may not be independent, and combining both may provide the optimal survival benefit. There is considerable scope for improving dietary pattern and PA, given that only half of breast cancer survivors report at least 9 metabolic equivalent tasks (MET) -h/wk3 and another half eat at least five daily servings of vegetables-fruits (VF).10 In this study, we examined the interactions between selected lifestyle factors and mortality in breast cancer survivors who might change lifestyle to improve prognosis. These women volunteered for a diet trial within 4 years of diagnosis and were randomly assigned to the comparison group of the ongoing Women's Healthy Eating and Living Study. Our goal was to establish a parsimonious set of lifestyle predictors for use in the final analysis of the Women's Healthy Eating and Living Study, which is investigating the effect of a plant-based diet on additional breast cancer events. First, we looked for univariate effects on survival of lifestyle variables measured at baseline and, using only variables with significant associations, we developed a combined lifestyle variable. We tested the combined variable in a multivariate model controlling for obesity and cancer and treatment characteristics.
Study Population This study considers 1,490 women, age 70 years at diagnosis of early-stage breast cancer (average age, 50 years), who resided in California, Oregon, Arizona, and Texas. All were originally diagnosed between 1991 and 2000, and randomly assigned to the control group in a dietary trial within 48 months of diagnosis (average, 24 months) between March 1995 and November 2000.10 Breast cancer stage from American Joint Committee on Cancer (6th edition)11 was as follows: 40% stage I ( 1 cm), 45% stage II, and 15% stage III, and all had completed primary therapy, although the majority were still taking tamoxifen. Medical records relating to the primary diagnosis provided details regarding tumor characteristics and treatment. Baseline questionnaires included information regarding adjuvant therapies. Institutional review board approval and written participant consent was obtained for conduct of the research.
Outcome Ascertainment
Lifestyle Assessments Physical activity. Physical activity was assessed at baseline using a nine-item questionnaire on usual PA,14 previously demonstrated to be both reliable15 and valid.16 This questionnaire queries frequency, duration, and speed of walking outside the home and frequency and duration of participating in each of three intensity levels of exercise: strenuous, moderate, or mild (with example activities for each level). Activity levels were converted into METs in accordance with Ainsworth et al17: mild activity was assessed as three METs, moderate activity was assessed as five METs, and vigorous activity was assessed as eight METs. For walking, slow, average, fast, and very fast were assessed as two, three, four, and six METs, respectively. Total energy expenditure for an activity was estimated as the product of time spent in activity (minutes) times METs.17 Other assessments. Height and weight were measured at a baseline clinic visit and body mass index (BMI; weight in kilograms/height in meters squared) was calculated. A short self-reported smoking history was collected at baseline.14 Lifetime alcohol consumption was assessed on a baseline questionnaire. For ever drinkers (> 12 drinks lifetime), we report the number of drinks/mo estimated from the 24-hour dietary recalls.
Statistical Methods
Initially, a multivariate model included all variables found to be significant in either the univariate categoric or the univariate trend analyses at the
Tumor and Treatment Characteristics and Mortality The average follow-up interval between original breast cancer diagnosis and censor point was 8.7 years, with an average of 6.7 years of follow-up after baseline data collection. As of December 1, 2005, this study group (n = 1,490) had accumulated 9,665 person-years of observation, during which time there were 236 breast cancer events and 135 deaths: 118 were attributable to breast cancer, 10 were attributable to other cancers, and only seven were attributable to noncancer mortality. In the univariate analysis (Table 1), as expected, tumor stage and grade were strongly related to mortality. Age, hormone receptor status, type of chemotherapy and adjuvant tamoxifen were not associated significantly with mortality.
Lifestyle Factors and Mortality Tables 2 and 3 present the univariate analyses of mortality for all lifestyle factors considered in our model. Less than 5% of participants were current smokers, averaging 11 cigarettes/d, and nearly 60% had never smoked. Smoking status was not associated with mortality (P = .45). Less than one third (29%) of these breast cancer survivors were current drinkers, with 7% classified as heavy drinkers (60 drinks/mo). Alcohol consumption showed an inverse association with mortality (P = .03).
BMI was related to mortality (P = .06) with an apparent J-shaped relationship and no significant linear trend. Women categorized as low BMI (BMI < 20; n = 77) had twice the mortality (15.6% v 7.1%) as women with BMI 20 to 24.99 or categorized as overweight (BMI = 25 to 29.99). Women categorized as obese (BMI 30) had a higher mortality rate than normal-weight participants (12.4% v 7.1%; P = .01). The median intake of VF was 4.93 servings/d. Consumption of VF was related to mortality (P = .02), although the trend was not linear (Ptrend = .08). Women who consumed fewer than 3.43 VF servings/d (quartile 1) experienced the highest mortality rate (12.4%). Mortality seemed to decrease with increasing intake to 5 VF servings/d. The mean reported energy intake was 1,722 kcal/d and was not associated with mortality. The median intake of fat was 28.5% of energy intake, with the highest quartile consuming more than 33% energy from fat and the lowest quartile consuming less than 24% energy from fat; however, mortality rates did not differ significantly across quartiles (P = .6), and a significant trend was not observed (Ptrend = .10). The lowest quartile of fiber consumption was less than 16 g/d and the highest was more than 25 g/d. The median fiber consumption was 20.2 g/d. Mortality did not differ across quartiles (P = .15) nor was there a linear trend (Ptrend = .12). The median level of PA was 636 MET-min/wk. Women who reported no PA (7.7%) had a mortality similar to other women in the lowest quartile and were combined with them. Mortality rates showed a linear trend (Ptrend = .02), with the highest mortality in the lowest quartile (< 225 MET -min/wk) and reduced mortality, particularly in the highest two quartiles.
Composite Dietary Pattern-PA Variable
Multivariate Regression Model of Mortality
The strong protective association of high VF/high PA with improved survivorship is also evident in the Kaplan-Meier survival curves (Fig 1): survival data from study enrollment through the December 2005 follow-up illustrates an estimated 10-year survival rate postdiagnosis of 93% in the high VF/high PA group, and 86% to 87% in the other three groups. Thus, the estimated absolute unadjusted mortality risk reduction was 6% to 7% at 10 years for women who achieved this pattern, compared with women who consumed fewer daily VF servings and/or performed less PA.
Figure 2 presents the mortality experience for categories of BMI and the composite VF-PA variable, comparing nonobese with obese women. For the nonobese group, there was no difference in mortality in the study period for women in any group other than the high VF/high PA group with estimated mortality percentage between 9.1% and 9.9%. Mortality among women in the high VF/high PA group (4.9%; 95% CI, 2.7% to 7.1%) was approximately half that of the other groups. For women who were obese, there was no difference in mortality in the same three study groups, with estimates from 12.7% to 14.2%. Again, there were significantly fewer deaths in the 16% of obese women classified in the high VF/high PA group (4.7%; 95% CI, 0% to 9.8%). Within each VF/PA category, women who were obese had an apparent increase in mortality compared with those who were not obese, except in the high VF/high PA group, where the observed mortality rates were comparable.
We also assessed whether the high VF/high PA lifestyle effect on survival was limited to women with hormone receptorpositive tumors (Fig 3), as might be expected if the mechanism of action was mediated by gonadal reproductive hormones. Univariate analysis showed no survival advantage for healthy lifestyle in estrogen receptornegative, progesterone receptornegative (ER negative, PR negative) group (P = .4), a borderline advantage for ER-negative, PR-positive group (P = .09), and significant advantages for ER-positive, PR-negative (P = .04) and ER-positive, PR-positive groups (P = .01).
Finally, we investigated cause of death and saw no difference in breast cancer versus other-cause mortality when stratified by the lifestyle variable (P = .37).
In these breast cancer survivors who were interested in lifestyle change and were predominantly nonsmokers, the 30% of women who were physically active and consumed at least 5 servings of vegetables and fruits each day had an estimated 10-year mortality rate of 7%, approximately half that of any other combination of PA and dietary pattern. Of particular importance, this halving of risk was seen in women who were not obese as well as in those who were obese. Indeed, it appeared that both being physically active and having a healthy dietary pattern attenuated the increase in risk observed among the obese. It was noted, however, that obese women were approximately one half as likely as nonobese women to be both physically active and to have a healthy dietary pattern. This study is not the first to suggest that a combination of healthy lifestyle behaviors is associated with improved survival, although it is the first, to our knowledge, in a population of breast cancer survivors. The European Healthy Aging study22 of 70- to 90-year-old men and women noted that being a nonsmoker, adhering to a Mediterranean diet, being physically active, and consuming alcohol in moderation were associated with a 60% reduction in cancer deaths as well as 60% reduction in all-cause mortality. Similarly, the Nurses' Health Study23 noted that 82% of coronary events could be attributed to lack of adherence to a similar combination of behaviors. Longitudinal follow-up of a population-based random survey of men and women in Hawaii demonstrated that a combination variable constructed from smoking status, BMI, dietary pattern, and alcohol use was strongly associated with mortality, including mortality from cancer.24 Accordingly, most recent guidelines for chronic disease prevention, including cancer,25 cardiovascular disease,26 and obesity,27 emphasize the importance of adhering to multiple lifestyle behaviors. Given that the number of cancer survivors is increasing, and breast cancer survivors make up the largest group of cancer survivors,28 it is important to consider the potential impact on prognosis of lifestyle changes such as diet and PA on women who have survived initial treatment. PA recommendations usually include duration (eg, 30 min/d), intensity (moderate, 3 to 6 METs; vigorous, 6+ METs) and frequency (eg, vigorous, 3 times/wk; moderate, 5+ times/wk). Accordingly, the absolute minimum recommendation for moderate activity would require 450 MET-min/wk. In this study, we chose a level 20% higher than this absolute minimum for classifying a participant as physically active; this allowed us to use an equivalent cut point to that used in the Nurses' Health Study.3 However, unlike the Nurses' Health Study, in the univariate analysis only, we found a significant linear association in which more activity was associated with increased benefit. It is important to note that the brief self-reported questionnaire has been shown to overestimate activity when compared with an accelerometer measure in our study population.16 The survival advantage for the high VF/high PA lifestyle was present in women who had ER-positive tumors, but not in those who were ER-negative, suggesting that the mechanism for action for this effect might be reproductive gonadal hormones, as has been suggested previously for each of the component lifestyle factors.8,9 It is likely that this observed effect is not simply an effect of adjuvant tamoxifen, which was prescribed to 45% of the study sample.10 The effect observed may vary in current populations because study participants were all diagnosed before the introduction of adjuvant aromatase inhibitor therapy. In summary, breast cancer survivors who consume a healthy diet and are physically active may increase their years of survival after diagnosis. Specifically, we have shown that those who reported eating a minimum of 5 VF servings daily and performing weekly PA equivalent to 30 minutes of walking at a moderate pace for 6 days a week had a higher 10-year survival rate than those who did not adhere to these lifestyle practices. The improved survival rate was observed in women who were obese as well as those who were not obese. Adhering to these two health behaviors reduced the probability of death in the follow-up period by 50%, whereas this effect was not seen if breast cancer survivors were adherent to only PA or VF dietary pattern. These findings suggest the need for additional study of the combined protective effect of diet and PA on breast cancer survival.
The author(s) indicated no potential conflicts of interest.
Conception and design: John P. Pierce Financial support: John P. Pierce, Marcia L. Stefanick, Cynthia A. Thomson, Bette Caan Administrative support: John P. Pierce, Marcia L. Stefanick, Shirley W. Flatt, Cynthia A. Thomson, Richard Hajek, Vicky A. Newman, Bette Caan Provision of study materials or patients: John P. Pierce Collection and assembly of data: John P. Pierce, Marcia L. Stefanick, Shirley W. Flatt, Cynthia A. Thomson, Richard Hajek, Barbara A. Parker, Vicky A. Newman, Bette Caan Data analysis and interpretation: John P. Pierce, Shirley W. Flatt, Loki Natarajan Manuscript writing: John P. Pierce, Marcia L. Stefanick, Shirley W. Flatt, Loki Natarajan, Barbara Sternfeld, Lisa Madlensky, Wael K. Al-Delaimy, Cynthia A. Thomson, Sheila Kealey, Barbara A. Parker, Bette Caan, Cheryl L. Rock Final approval of manuscript: John P. Pierce, Marcia L. Stefanick, Shirley W. Flatt, Barbara Sternfeld, Lisa Madlensky, Wael K. Al-Delaimy, Cynthia A. Thomson, Sheila Kealey, Barbara A. Parker, Bette Caan, Cheryl L. Rock
The following institutions participated in The Women's Healthy Eating and Living (WHEL) Study: WHEL Study Coordinating Center: University of California, San Diego, Cancer Prevention and Control Program, San Diego, CA: Dr John P. Pierce (Principal Investigator), Dr Barbara Parker (Medical Director), Susan Faerber, Shirley Flatt, Sheila Kealey, Dr Loki Natarajan, Vicky Newman, Dr Cheryl L. Rock; WHEL Study Clinic Sites: Center for Health Research, Portland, OR: Dr Njeri Karanja, Dr Mark Rarick; Kaiser Permanente Northern California, Oakland, CA: Dr Bette J. Caan, Dr Lou Fehrenbacher; Northern California Cancer Center, Palo Alto, CA: Dr Marcia L. Stefanick, Dr Robert Carlson; University of Arizona, Tucson and Phoenix, AZ: Dr Cynthia Thomson, Dr James Warnecke; University of California, Davis, Davis, CA: Dr Ellen B. Gold, Dr Sidney Scudder; University of California, San Diego Cancer Center, San Diego, CA: Dr Kathryn A. Hollenbach, Dr Linda Wasserman; University of Texas M.D. Anderson Cancer Center, Houston, TX: Dr Lovell A. Jones, Dr Richard Theriault.
Supported by the Walton Family Foundation, and support continued with funding from National Cancer Institute Grant No. CA 69375 for The Women's Healthy Eating and Living (WHEL) Study. Some of the data were collected from General Clinical Research Centers, National Institutes of Health Grants No. M01-RR00070, M01-RR00079, and M01-RR00827. The National Cancer Institute played no role in the design and conduct of this study; collection, management, analysis, and interpretation of the data; or preparation, review, or approval of the manuscript. Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.
1. Rock CL, Flatt SW, Natarajan L, et al: Plasma carotenoids and recurrence-free survival in women with a history of breast cancer. J Clin Oncol 23:6631-6638, 2005 2. Zhang S, Folsom AR, Sellers TA, et al: Better breast cancer survival for postmenopausal women who are less overweight and eat less fat: The Iowa Women's Health Study. Cancer 76:275-283, 1995[CrossRef][Medline] 3. Holmes MD, Chen WY, Feskanich D, et al: Physical activity and survival after breast cancer diagnosis. JAMA 293:2479-2486, 2005 4. Bastarrachea J, Hortobagyi GN, Smith TL, et al: Obesity as an adverse prognostic factor for patients receiving adjuvant chemotherapy for breast cancer. Ann Intern Med 120:18-25, 1994 5. Obermair A, Kurz C, Hanzal E, et al: The influence of obesity on the disease-free survival in primary breast cancer. Anticancer Res 15:2265-2269, 1995[Medline] 6. Rohan TE, Fu W, Hiller JE: Physical activity and survival from breast cancer. Eur J Cancer Prev 4:419-424, 1995[CrossRef][Medline] 7. Kroenke CH, Fung TT, Hu FB, et al: Dietary patterns and survival after breast cancer diagnosis. J Clin Oncol 23:9295-9303, 2005 8. Rock CL, Demark-Wahnefried W: Nutrition and survival after the diagnosis of breast cancer: A review of the evidence. J Clin Oncol 20:3302-3316, 2002 9. Broocks A, Pirke KM, Schweiger U, et al: Cyclic ovarian function in recreational athletes. J Appl Physiol 68:2083-2086, 1990 10. Pierce JP, Faerber S, Wright FA, et al: A randomized trial of the effect of a plant-based dietary pattern on additional breast cancer events and survival: The Women's Healthy Eating and Living (WHEL) Study. Control Clin Trials 23:728-756, 2002[CrossRef][Medline] 11. American Joint Committee on Cancer.Manual for Staging of Cancer (ed 6). New York, NY, Springer-Verlag, 2002 12. Pierce JP, Newman VA, Flatt SW, et al: Telephone counseling intervention increases intakes of micronutrient- and phytochemical-rich vegetables, fruit and fiber in breast cancer survivors. J Nutr 134:452-458, 2004 13. Natarajan L, Flatt SW, Sun X, et al: Validity and systematic error in measuring carotenoid consumption with dietary self-report instruments. Am J Epidemiol 163:770-778, 2006 14. Design of the Women's Health Initiative clinical trial and observational study: The Women's Health Initiative Study Group. Control Clin Trials 19:61-109, 1998[CrossRef][Medline] 15. Langer RD, White E, Lewis CE, et al: The Women's Health Initiative Observational Study: Baseline characteristics of participants and reliability of baseline measures. Ann Epidemiol 13:S107-S121, 2003[CrossRef][Medline] 16. Johnson-Kozlow M, Rock CL, Gilpin EA, et al: Validation of WHI brief physical activity questionnaire among women diagnosed with breast cancer. Am J Health Behav 31:193-202, 2007[Medline] 17. Ainsworth BE, Haskell WL, Whitt MC, et al: Compendium of physical activities: An update of activity codes and MET intensities. Med Sci Sports Exerc 32:S498-S504, 2000 18. Goodwin PJ, Ennis M, Pritchard KI, et al: Fasting insulin and outcome in early-stage breast cancer: Results of a prospective cohort study. J Clin Oncol 20:42-51, 2002 19. Suissa S, Pollak M, Spitzer WO, et al: Body size and breast cancer prognosis: A statistical explanation of the discrepancies. Cancer Res 49:3113-3116, 1989 20. Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults: Executive summaryExpert Panel on the Identification, Evaluation, and Treatment of Overweight in Adults. Am J Clin Nutr 68:899-917, 1998[Medline] 21. Therneau TM, Grambsch PM: Modeling Survival Data: Extending the Cox Model, Statistics for Biology and Health. New York, NY, Springer-Verlag, 2000 22. Knoops KT, de Groot LC, Kromhout D, et al: Mediterranean diet, lifestyle factors, and 10-year mortality in elderly European men and women: The HALE project. JAMA 292:1433-1439, 2004 23. Stampfer MJ, Hu FB, Manson JE, et al: Primary prevention of coronary heart disease in women through diet and lifestyle. N Engl J Med 343:16-22, 2000 24. Meng L, Maskarinec G, Lee J, et al: Lifestyle factors and chronic diseases: Application of a composite risk index. Prev Med 29:296-304, 1999[CrossRef][Medline] 25. Byers T, Nestle M, McTiernan A, et al: American Cancer Society guidelines on nutrition and physical activity for cancer prevention: Reducing the risk of cancer with healthy food choices and physical activity. CA Cancer J Clin 52:92-119, 2002 26. Krauss RM, Eckel RH, Howard B, et al: AHA Dietary Guidelines: Revision 2000: A statement for healthcare professionals from the Nutrition Committee of the American Heart Association. Circulation 102:2284-2299, 2000 27. USDHHS: Dietary Guidelines for Americans, 2005. Washington, DC, US Department of Health and Human Services, 2005 28. CDC: Cancer SurvivorshipUnited States, 1971-2001. MMWR Morb Mortal Wkly Rep 53:526-529, 2004[Medline] Submitted August 10, 2006; accepted December 14, 2006. This article has been cited by other articles:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|||||||||||
|
Copyright © 2007 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
|