Journal of the National Cancer Institute Advance Access originally published online on July 7, 2009
JNCI Journal of the National Cancer Institute 2009 101(14):984-992; doi:10.1093/jnci/djp175
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© The Author 2009. Published by Oxford University Press.
ARTICLES |
Racial Disparities in Cancer Survival Among Randomized Clinical Trials Patients of the Southwest Oncology Group
Affiliations of authors: Department of Medicine, Loyola University Chicago Stritch School of Medicine, Maywood, IL (KSA); Southwest Oncology Group Statistical Center, Seattle, WA (JMU, JJC); University of Texas Health Science Center at San Antonio, San Antonio, TX (CAC); Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY (DLH)
Correspondence to: Kathy S. Albain, MD, Loyola University Medical Center, Cardinal Bernardin Cancer Center, 2160 South First Ave, Maywood, IL 60153-5589 (e-mail: kalbain{at}lumc.edu); Group Chair’s Office, Southwest Oncology Group, 24 Frank Lloyd Wright Dr, PO Box 483, Ann Arbor, MI 48106-0483 (e-mail: arlauska{at}med.umich.edu).
Background: Racial disparities in cancer outcomes have been observed in several malignancies. However, it is unclear if survival differences persist after adjusting for clinical, demographic, and treatment variables. Our objective was to determine whether racial disparities in survival exist among patients enrolled in consecutive trials conducted by the Southwest Oncology Group (SWOG).
Methods: We identified 19 457 adult cancer patients (6676 with breast, 2699 with lung, 1244 with colon, 1429 with ovarian, and 1843 with prostate cancers; 1291 with lymphoma; 2067 with leukemia; and 2208 with multiple myeloma) who were treated on 35 SWOG randomized phase III clinical trials from October 1, 1974, through November 29, 2001. Patients were grouped according to studies of diseases with similar histology and stage. Cox regression was used to evaluate the association between race and overall survival within each disease site grouping, controlling for available prognostic factors plus education and income, which are surrogates for socioeconomic status. Median and ten-year overall survival estimates were derived by the Kaplan–Meier method. All statistical tests were two-sided.
Results: Of 19 457 patients registered, 2308 (11.9%, range = 3.9%–21.6%) were African American. After adjustment for prognostic factors, African American race was associated with increased mortality in patients with early-stage premenopausal breast cancer (hazard ratio [HR] for death = 1.41, 95% confidence interval [CI] = 1.10 to 1.82; P = .007), early-stage postmenopausal breast cancer (HR for death = 1.49, 95% CI = 1.28 to 1.73; P < .001), advanced-stage ovarian cancer (HR for death = 1.61, 95% CI = 1.18 to 2.18; P = .002), and advanced-stage prostate cancer (HR for death = 1.21, 95% CI = 1.08 to 1.37; P = .001). No statistically significant association between race and survival for lung cancer, colon cancer, lymphoma, leukemia, or myeloma was observed. Additional adjustments for socioeconomic status did not substantially change these observations. Ten-year (and median) overall survival rates for African American vs all other patients were 68% (not reached) vs 77% (not reached), respectively, for early-stage, premenopausal breast cancer; 52% (10.2 years) vs 62% (13.5 years) for early-stage, postmenopausal breast cancer; 13% (1.3 years) vs 17% (2.3 years) for advanced ovarian cancer; and 6% (2.2 years) vs 9% (2.7 years) for advanced prostate cancer.
Conclusions: African American patients with sex-specific cancers had worse survival than white patients, despite enrollment on phase III SWOG trials with uniform stage, treatment, and follow-up.
| CONTEXT AND CAVEATS Prior knowledge Racial disparities have been observed in outcomes for several malignancies, but it is unclear whether these differences remain after adjusting for clinical, demographic, and treatment variables. Study design Study subjects were adult cancer patients with lymphoma, leukemia, or multiple myeloma or with breast, lung, colon, ovarian, or prostate cancers who were treated on 35 Southwest Oncology Group randomized phase III clinical trials and who received uniform treatment and follow-up. Patients were grouped according to diseases with similar histology and stage. Associations between race and overall survival within each disease site grouping were studied, controlling for prognostic, treatment, and socioeconomic factors. Contribution After adjustment for prognostic factors, African American race was associated with increased mortality from early-stage premenopausal breast cancer, early-stage postmenopausal breast cancer, advanced-stage ovarian cancer, and advanced-stage prostate cancer but not from lung cancer, colon cancer, lymphoma, leukemia, or myeloma. Associations did not change after additional adjustment for socioeconomic status. Implications Unrecognized interactions of tumor biological, hormonal, and/or inherited host factors may be contributing to differential survival outcomes by race in sex-specific malignancies. Limitations Cancers of non–African American patients may have been more likely detected through screening than those of African American patients for breast cancer and prostate cancer. Some racial disparities in overall survival may be related to disparities in noncancer health and comorbid disease. Racial disparities in adherence to hormonal therapy prescribed in trials may have occurred. From the Editors
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Manuscript received October 24, 2008; revised May 8, 2009; accepted May 15, 2009.
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J Natl Cancer Inst 2009 101: 969.
J Natl Cancer Inst 2009 101: 969.
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