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Small samples with few minority women and/or the absence of comparisons to peers without cancer histories have limited previous research suggesting racial differences in breast cancer survivors’ health-related quality of life (HRQoL). The present study not only compares HRQoL of African American and white breast cancer survivors, but also compares the HRQoL of these women to that of same race women with no cancer history.
Data from the Women’s Health Initiative-Observational Study were used including 5,021 cancer survivors and 88,532 women without a history of cancer. Multivariable regression analyses estimated differences in breast cancer survivors’ baseline HRQoL (RAND36), depressive symptoms (CES-D short-form), and sleep quality (WHIIRS).
African American breast cancer survivors reported worse physical functioning and general health compared to white survivors. Among African Americans, survivors reported worse role limitations due to physical health, pain, general health, and vitality than women without a history of cancer. This was most evident in those with more recent diagnoses. Most significant differences between groups were small in magnitude (Cohen’s d=.21-.36).
These results add to the increasing knowledge of cancer disparities by showing that African American women have small but clinically meaningful decrements in physical HRQoL compared to white survivors and to African American women without cancer. Since African American women also face diagnosis with higher grade tumors and higher breast cancer mortality, more research is needed to examine the physical and psychosocial experiences of African American breast cancer survivors to elucidate the mechanisms leading to poorer outcomes.
Breast cancer is the most frequently diagnosed cancer among women (excluding nonmelanoma skin cancer), regardless of race1. Earlier detection and treatment improvements have significantly increased five-year survival rates in the last three decades1. As more women survive breast cancer, it is important to examine the factors that influence quality of life among survivors.
The psychological and physical impact of breast cancer is considerable during the period of diagnosis and treatment 2 and may continue for several years after treatment 3. These adverse effects can impact health-related quality of life (HRQoL), a term that encompasses physical, social, spiritual, economic, and psychological well-being 4,5. A review of the cancer survivorship literature suggests the need to investigate socioeconomic and cultural variables that may differentially impact the quality and quantity of survival 6. Among the most important of these are race and ethnicity. Age-adjusted breast cancer incidence rates are lower for African American women than white women1; however, African American women have more high grade and estrogen receptor negative tumors contributing to higher breast cancer mortality7. Breast cancer disparities may extend to HRQoL outcomes as well. Research regarding racial and ethnic differences in HRQoL is sparse and has been limited by small samples with few racial or ethnic minority women and/or the absence of comparison samples of women without a history of cancer. Nonetheless, differences between white and African American breast cancer survivors have been suggested including differences in the strategies used to cope with cancer and its aftermath 8, differential predictors of physical and emotional functioning 9-11, and lower social functioning 12 and physical functioning outcomes 10,13 among African Americans.
The Women’s Health Initiative (WHI), the largest study of women’s health conducted to date, provided a unique opportunity to examine HRQoL among African American and white breast cancer survivors and women without a history of cancer and thus eliminate many of the methodological problems of past studies. The enrollment of a substantial number of African American breast cancer survivors (n=465), allowed for comparisons between survivors and same-race women without a cancer history as well as between African American and white breast cancer survivors.
The WHI-OS enrolled 93,676 women from 1994-1998 14. Postmenopausal women ages 50 to 79 were self-identified from the general population living in proximity to 40 participating WHI Clinical Centers 14. Women became participants in the WHI-OS by responding to a direct invitation to be screened or by being ineligible for or unwilling to enroll in the clinical trial components. Women were screened according to the following eligibility criteria: plans to reside in the area for at least three years, an absence of medical conditions predictive of less than three years of survival, an absence of complicating conditions such as alcoholism, drug dependency or dementia, and a willingness and ability to provide written informed consent. At enrollment, 5% (n=5,021) of the participants reported a prior breast cancer diagnosis, including 465 African American survivors. The Institutional Review Boards at all of the participating institutions approved the protocols and procedures. Details of the scientific rationale, eligibility, recruitment strategies, and other design aspects of the WHI-OS have been published elsewhere 15.
At baseline, WHI-OS participants completed a battery of self-administered and interviewer-administered questionnaires. Clinic personnel reviewed forms for completion and data were entered and stored in the WHI data system. A subset of the questionnaires chosen for study here were those relevant to current HRQoL.
Depression was measured using a depression-screening algorithm first developed for use in the National Study of Medical Care Outcomes (MOS) 19. Higher scores indicate more frequent depressive symptoms.
Developed and validated for use in the WHI, the WHIIRS assesses sleep quality, including sleep initiation and maintenance 20,21. Items are summed and total scores range from 4 to 24 with higher scores indicating greater sleep disturbance.
The WHI baseline survey also included items pertaining to demographics 14, co-morbidities, and other conditions that may impact survivors’ HRQoL such as menopausal symptoms, osteoporosis, and hospitalizations. A co-morbidity index was constructed from 27 WHI-OS items that asked about various conditions, such as stomach ulcers, heart and circulation problems, arthritis, and migraine headaches. Dichotomous responses with 1=yes and 0=no were summed to create an overall score, ranging from 0-27. Higher scores indicate greater morbidity.
Eleven items based on measures used in the Alameda County Study 22, and later adapted for use in the Beta-Blocker in Heart Attack Trial 23 were used to assess life events. These items were modified to make them more relevant to major life events in the lives of older women (e.g., divorce, conflict with children or grandchildren, death of spouse). Item scores were summed to create a total life events score, and ranged from 0-11. Higher scores indicated a greater number of stressful life events.
Sociodemographic characteristics of breast cancer survivors and women without a cancer history were compared using t-tests and χ2 tests. Analyses were stratified by race. Women in the WHI-OS were excluded from the non-cancer comparison group if they reported any cancer diagnosis in their lifetime (n=4,138).
Multivariable linear regression models compared HRQoL between WHI-OS breast cancer survivors (n=5,021) and women without a cancer diagnosis at baseline (n=88,532). Stratified analyses were then used to compare African American (n=465) and white (n=4,446) breast cancer survivors to women of the same race without a cancer history (n=6641; 67,027; respectively). Comparisons of survivors’ HRQoL between races were also conducted. Based on prior work suggesting predictors of breast cancer survivors’ HRQoL that differ by race, multivariable analyses adjusted for age at study entry, education, experience of stressful life events, and co-morbidity24.
Previous studies have shown that time since diagnosis is correlated with HRQoL 25-27. Unfortunately, the WHI-OS baseline survey did not include the participants’ date of breast cancer diagnosis or treatment information. Therefore, date of diagnosis was approximated by stratifying the sample by timing of diagnosis (< age 55 or > age 55) and controlling for age at study entry in the analysis.
To decrease the possibility of spurious significant results due to the number of comparisons, a Bonferroni-adjusted alpha level of 0.005 (0.05/10 comparisons) was used to assess statistical significance. To assess clinical significance of these results, we determined the effect size for the differences in HRQoL between groups using Cohen’s d. Effect sizes of 0.20-0.49 are considered small, 0.50-0.79 as medium, and ≥0.80 as large28.
Table 1 shows demographic characteristics of the participants by race and cancer history. The largest age group was 60 to 69 year olds. The majority of the participants had completed at least high school and approximately three-fifths reported family incomes over $35,000. Approximately, 48% of white breast cancer survivors and 56% of African American breast cancer survivors were diagnosed before the age of 55. Among white women, the average number of non-cancer co-morbid conditions appeared to be greater among breast cancer survivors (mean=2.77), than women without a cancer history (mean=2.40; p<.001). This difference was not observed among African American women. Breast Cancer Survivors of Both Races Combined compared to Women Without a History of Cancer
In adjusted models (Table 2), breast cancer survivors reported worse physical functioning (β=−1.02, p<0.001), greater role limitations due to physical health (β=−2.46; p<0.001), more pain (β=−1.16; p<0.001), worse general health (β=−3.38; p<0.001), less vitality (β=−1.21; p<0.001), better social functioning (β=0.96; p<0.001), less sleep disturbance (β=−0.38; p<0.001), and more depressive symptoms (β= 0.01; p=0.002) than women without a history of cancer. However, none of these differences achieved even Cohen’s threshold for small effects (largest Cohen’s d=0.18 for general health).
As shown in Table 3, African American breast cancer survivors had significantly worse general health (β=-4.61; p<0.001), and less vitality (β=−2.99, p=0.001) than African American women without a history of cancer. However, only the difference in general health (Cohen’s d=0.23) achieved Cohen’s threshold for small effects. There were no other significant differences between African American survivors and African American women without a history of cancer.
White breast cancer survivors reported significantly lower physical functioning (β = −1.00; p=0.001), more role limitations due to physical health (β=−2.29; p<0.001), more bodily pain (β=−1.23; p<0.001), worse general health (β = −3.36; p<0.001), less vitality (β=−1.13; p<0.001), and less sleep disturbance (β= −0.34; p<0.001) compared to white women without a history of cancer. None of these differences even achieved Cohen’s threshold for small effects (largest Cohen’s d=0.18 for general health). No differences were observed in social functioning, role limitations due to emotional health, emotional well-being, or depression between white survivors and white women without a history of cancer.
African American survivors were next compared to white survivors to examine racial differences in survivors’ quality of life (Table 4). In adjusted models, African American survivors reported lower physical functioning, (β=−8.07; p<0.001) and general health (β=−5.99, p<0.001), and greater role limitations due to emotional health (β=−4.95, p=0.001) compared to white survivors. The differences in physical functioning (Cohen’s d=0.36) and general health (Cohen’s d=0.31) achieved the threshold for small effects. There were no other differences detected between African American and white survivors.
By stratifying on whether the breast cancer diagnosis occurred before or after age 55 and then controlling for age at study entry, we were able to examine the relationship between the approximate time since diagnosis and HRQoL (Table 5). Among white women, survivors diagnosed before age 55 had significantly worse general health (β=−3.33; p<0.001) and less sleep disturbance (β = −0.33; p<0.001) than those without a history of cancer; however, neither difference achieved the threshold for small effects. White breast cancer survivors diagnosed after age 55 reported lower levels of physical functioning (β=−1.62; p<0.001), greater role limitations due to physical health (β=−2.98; p<0.001), more pain (β=−1.65; p<0.001) poorer general health (β=−3.36; p<0.001), lower energy levels (β =−1.45; p< 0.001),and less sleep disturbance (β=−0.35; p<0.001) than white women without a cancer history. However, again, none of these differences achieved even Cohen’s threshold for small effects.
Among African American participants, survivors diagnosed before age 55 had HRQoL comparable to that of their African American peers without a cancer history, with the exception of lower scores on the general health scale (β=−3.89; p<0.001) where again, the difference did not achieve the threshold for small effects (Cohen’s d=0.19). However, African American breast cancer survivors diagnosed after age 55 reported worse role limitations due to physical health (β=−8.44; p=0.002), pain (β=−5.48; p=0.004), general health (β=−5.32; p<0.001), and vitality levels (β=−4.35; p=0.002) than African American women without a history of cancer. All of these differences reached the threshold for small effects (Cohen’s d=0.21, 0.21, 0.29, and 0.22, respectively).
Previous studies examining HRQoL among different racial/ethnic groups of breast cancer survivors have identified important differences between racial groups 8,9,24,29, but have been limited by small sample sizes and a general lack of comparison to women without a history of cancer.
This study presents the first comparison of breast cancer survivors with similar women without a cancer history on a variety of HRQoL measures using a large sample of white and African American women. The unique nature of this study makes a novel contribution to the literature by allowing African American and white breast cancer survivors’ HRQoL to be compared both to each other and with that of same race women who did not have a history of cancer.
Overall, this study found that although African American breast cancer survivors reported significantly lower scores on many domains of HRQoL compared to white survivors, these differences were very small and likely not clinically meaningful, with two exceptions. African American survivors reported significantly lower physical functioning and general health than white survivors. While the magnitude of these differences is considered small according to Cohen’s rule of thumb, these likely represent clinically significant racial differences, and corroborate previous research 10,30. Further, these results extend previous studies by also noting that the general health levels reported by African American breast cancer survivors were also significantly worse than African American women without a history of cancer. Among African American survivors diagnosed more recently, this was also true for other aspects of physical HRQoL, including role limitations due to physical health, pain, and vitality. The magnitude of these differences is considered small, but likely represents clinically meaningful decrements in physical HRQoL among African American breast cancer survivors compared to African American women without a history of cancer. These findings were evident even after adjusting for a number of factors shown to contribute to lower HRQoL among African American survivors including socioeconomic status indicators, stressful life events, and co-morbidities24. These results suggest either a greater perceived impact from cancer or factors such as co-morbidities among African American survivors or a greater prevalence of other physical limitations not measured by our surveys.
In contrast to previous work showing lower social functioning of African American compared to white breast cancer survivors 12, this study found no differences in social functioning between African American and white breast cancer survivors, or between African American or white survivors and their same race comparison groups of women without a history of cancer. The results of this study do not support a disparity in social functioning between African American and white breast cancer survivors; however, these results could be reflective of the inclusion of only healthy survivors in the WHI.
Unlike previous research showing higher mental health and emotional well-being among African American survivors 9,10, this study did not find differences in emotional well-being between African American and white survivors. This again could be due to the inclusion of only healthy survivors in the WHI. There did appear to be more role limitations due to emotional health among African American than white breast cancer survivors, however, possibly due to lingering concerns about cancer 24,31.
Although our study makes several important contributions to research on health disparities, cancer survivor and HRQoL research, the following weaknesses should be acknowledged. First, while the large sample size has the advantage of allowing within-race comparisons, it is possible that some of the statistical differences observed may not be clinically significant. We limited this bias by using a Bonfferoni-corrected p value and by calculating effect sizes using Cohen’s d to point to clinically meaningful results. Second, since we could not directly adjust for time since diagnosis or cancer treatment received, these results may gloss over important differences in HRQoL from timing and experience of treatment. Additionally, the more aggressive breast cancers experienced by African American women may be more likely to require chemotherapy, which could mean some of the racial differences reported here may actually reflect differences due to chemotherapy. Third, we were unable to address the economic domain of HRQoL due to a lack of relevant variables in WHI. It is possible that there could be differences between the groups on economic issues such as loss of work, income, health care costs, or career advancement. Fourth, due to lower numbers of breast cancer survivors in women in other racial/ethnic categories recruited to WHI, we could not address the role of race or ethnicity beyond comparisons of African American and white women. Additionally, WHI is not a population-based sample of any racial group and so the results may not be generalizable to the larger population of cancer survivors. Finally, the results are based on cross-sectional comparisons; longitudinal follow-up of the breast cancer survivors’ cohort and women without a history of cancer could reveal interesting patterns based on reoccurrences, new diagnoses, and long term adjustment.
Despite the above weaknesses, however, this study has several important strengths. This study is the first comparison of the HRQoL of African American and white breast cancer survivors both to each other and with similar women without a cancer diagnosis using a variety of HRQoL measures. In addition, quality of life data were collected on participants’ current functioning, rather than retrospectively asking women to report their HRQoL before and after diagnosis. The relatively large number of African American women included in this sample enabled stratification by race. As a result, this report offers several unique contributions to research examining HRQoL among breast cancer survivors by race.
These results suggest that the experiences of breast cancer survivors cannot be generalized across broad groups of women. Focusing future research on demographic subgroups of survivors will help elucidate differences in survivors’ HRQoL and allow research and clinical resources to be focused where they are most needed. These results help develop the emerging picture of cancer survivorship disparities. Not only do African American women face diagnosis with higher grade tumors and higher breast cancer mortality as demonstrated in prior work7, but the results of this study reveal that they also have small but clinically meaningful decrements in physical HRQoL compared to white survivors and to African American women without cancer. More research is needed to examine the physical and psychosocial experience of African American breast cancer survivors to elucidate the mechanisms leading to their poorer outcomes.
We wish to thank all WHI investigators and participants for their contributions. The following list is a short list of WHI investigators.
Program Office: (National Heart, Lung, and Blood Institute, Bethesda, Maryland) Elizabeth Nabel, Jacques Rossouw, Shari Ludlam, Linda Pottern, Joan McGowan, Leslie Ford, and Nancy Geller.
Clinical Coordinating Center: (Fred Hutchinson Cancer Research Center, Seattle, WA) Ross Prentice, Garnet Anderson, Andrea LaCroix, Charles L. Kooperberg, Ruth E. Patterson, Anne McTiernan; (Wake Forest University School of Medicine, Winston-Salem, NC) Sally Shumaker; (Medical Research Labs, Highland Heights, KY) Evan Stein; (University of California at San Francisco, San Francisco, CA) Steven Cummings.
Clinical Centers: (Albert Einstein College of Medicine, Bronx, NY) Sylvia Wassertheil-Smoller; (Baylor College of Medicine, Houston, TX) Jennifer Hays; (Brigham and Women’s Hospital, Harvard Medical School, Boston, MA) JoAnn Manson; (Brown University, Providence, RI) Annlouise R. Assaf; (Emory University, Atlanta, GA) Lawrence Phillips; (Fred Hutchinson Cancer Research Center, Seattle, WA) Shirley Beresford; (George Washington University Medical Center, Washington, DC) Judith Hsia; (Los Angeles Biomedical Research Institute at Harbor- UCLA Medical Center, Torrance, CA) Rowan Chlebowski; (Kaiser Permanente Center for Health Research, Portland, OR) Evelyn Whitlock; (Kaiser Permanente Division of Research, Oakland, CA) Bette Caan; (Medical College of Wisconsin, Milwaukee, WI) Jane Morley Kotchen; (MedStar Research Institute/Howard University, Washington, DC) Barbara V. Howard; (Northwestern University, Chicago/Evanston, IL) Linda Van Horn; (Rush Medical Center, Chicago, IL) Henry Black; (Stanford Prevention Research Center, Stanford, CA) Marcia L. Stefanick; (State University of New York at Stony Brook, Stony Brook, NY) Dorothy Lane; (The Ohio State University, Columbus, OH) Rebecca Jackson; (University of Alabama at Birmingham, Birmingham, AL) Cora E. Lewis; (University of Arizona, Tucson/Phoenix, AZ) Tamsen Bassford; (University at Buffalo, Buffalo, NY) Jean Wactawski-Wende; (University of California at Davis, Sacramento, CA) John Robbins; (University of California at Irvine, CA) F. Allan Hubbell; (University of California at Los Angeles, Los Angeles, CA) Howard Judd; (University of California at San Diego, LaJolla/Chula Vista, CA) Robert D. Langer; (University of Cincinnati, Cincinnati, OH) Margery Gass; (University of Florida, Gainesville/Jacksonville, FL) Marian Limacher; (University of Hawaii, Honolulu, HI) David Curb; (University of Iowa, Iowa City/Davenport, IA) Robert Wallace; (University of Massachusetts/Fallon Clinic, Worcester, MA) Judith Ockene; (University of Medicine and Dentistry of New Jersey, Newark, NJ) Norman Lasser; (University of Miami, Miami, FL) Mary Jo O’Sullivan; (University of Minnesota, Minneapolis, MN) Karen Margolis; (University of Nevada, Reno, NV) Robert Brunner; (University of North Carolina, Chapel Hill, NC) Gerardo Heiss; (University of Pittsburgh, Pittsburgh, PA) Lewis Kuller; (University of Tennessee, Memphis, TN) Karen C. Johnson; (University of Texas Health Science Center, San Antonio, TX) Robert Brzyski; (University of Wisconsin, Madison, WI) Gloria E. Sarto; (Wake Forest University School of Medicine, Winston-Salem, NC) Denise Bonds; (Wayne State University School of Medicine/Hutzel Hospital, Detroit, MI) Susan Hendrix.
Funded by: The National Heart, Lung and Blood Institute, U.S. Department of Health and Human Services. Portions of this work were funded by a grant from the National Cancer Institute CA131029. No portions of the analyses presented here have been presented elsewhere.
Condensed abstract: In the Women’s Health Initiative-Observational Study, African American breast cancer survivors reported small but clinically meaningful decrements in physical health-related quality of life compared to white survivors and to African American women without cancer.