CORRESPONDENCE

Re: Association of African-American Ethnic Background With Survival in Men With Metastatic Prostate Cancer

Anthony P. Polednak

Correspondence to: Anthony P. Polednak, Ph.D., Connecticut Tumor Registry, Connecticut Department of Public Health, 410 Capitol Ave., Hartford, CT 06134–0308 (e-mail: anthony. polednak{at}po.state.ct.us).

Thompson et al. (1) recently reported statistically significantly higher all-cause mortality in 288 African-American men than in 975 white men (hazard ratio = 1.23 and 95% confidence interval [CI] = 1.04 to 1.47, from a multivariate proportional hazards model that included prognostic variables) with metastatic prostate cancer. Although the authors (1) mentioned "education and poverty" as possible reasons for the difference in mortality, data on socioeconomic status (SES) were not included; "possible biologic differences" and genetic factors related to prostate cancer were discussed extensively (1). Although genetic explanations should not be overlooked, racial–ethnic comparisons should include some measure of SES (2). Analyses of clinical trial results could include coding the address of each patient to a census tract (or block group) and obtaining ecologic indicators of SES from census reports. Discussions of black–white differences in outcome from a clinical trial of colon cancer emphasized the lack of data on SES and the effect of mortality from causes other than cancer (3,4).

Although observational studies from cancer registries cannot provide the same degree of control for treatment and clinical characteristics as clinical trials (1), a study in the San Francisco Bay Area region of Surveillance, Epidemiology, and End Results (SEER)1 (5) reported that the risk of death from prostate cancer was statistically significantly greater among African-American than among white patients diagnosed in 1973–1993 at any stage when age, SES variables (census-tract level), and stage were included; however, tumor grade was not included, because it was not available for all years of diagnosis.

I examined data from the Connecticut registry (in the SEER Program) on 2719 white and 302 African-American men diagnosed in 1988–1995 with prostate cancer (as their only or first reportable cancer) that had spread beyond the prostatic capsule (SEER extent-of-disease codes 50–85) and/or to lymph nodes. The poverty rate of the census tract of residence at diagnosis in tertiles (based on data for African-American patients) was used as an SES indicator. Grade III or IV (6) tumors were more common among African-Americans than among whites (43% versus 36%), as was metastasis to viscera, bone, or unspecified site (66% versus 53%). Cox proportional hazards regression was used to examine risk of death (through 1998) from prostate cancer (underlying cause, 1088 deaths out of 1830). The adjusted risk ratios for age, grade, and extent of disease were statistically significant but not that for African-Americans versus whites (1.13; 95% CI = 0.93 to 1.38; P = .21) (Table 1Go). The latter risk ratio, however, was 1.20 (95% CI = 1.00 to 1.44; P = .046) in another model (not shown) that excluded the SES variable. When tumor grade (instead of SES) was excluded from the model, the risk ratio for prostate cancer mortality in African-Americans versus whites was statistically significant (1.25; 95% CI = 1.03 to 1.52; P = .027; data not shown ), as in the San Francisco study (5). Although the black–white difference in tumor grade is unexplained, nonbiologic mechanisms could be involved (5).


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Table 1. Cox proportional hazards regression model for mortality from prostate cancer among black and white Connecticut residents diagnosed with prostate cancer (extending beyond the prostate) in 1988–1995
 
For the clinical trial reported by Thompson et al. (1), it would be important to know the results of models that included an SES variable(s).

NOTES

1 Editor's note: SEER is a set of geographically defined, population-based, central cancer registries in the United States, operated by local nonprofit organizations under contract to the National Cancer Institute (NCI). Registry data are submitted electronically without personal identifiers to the NCI on a biannual basis, and the NCI makes the data available to the public for scientific research. Back

Supported in part by Public Health Service contract N01CN67005 from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services, with the Connecticut Department of Public Health.

REFERENCES

1 Thompson IM, Tangen CM, Tolcher A, Crawford ED, Eisenberger M, Moinpour CM. Association of African-American ethnic background with survival in men with metastatic prostate cancer. J Natl Cancer Inst 2001;93:219–25.[Abstract/Free Full Text]

2 Lin SS, Kelsey JL. Use of race and ethnicity in epidemiologic research: concepts, methodological issues, and suggestions for research. Epidemiol Rev 2000;22:187–202.[Medline]

3 Dignam JJ, Colangelo L, Tian W, Jones J, Smith R, Wickerham DL, et al. Outcomes among African-Americans and Caucasians in colon cancer adjuvant therapy trials: findings from the National Surgical Adjuvant Breast and Bowel Project. J Natl Cancer Inst 1999;91:1933–40.[Abstract/Free Full Text]

4 Brawley OW, Freeman HP. Race and outcomes: is this the end of the beginning for minority health research? [editorial]. J Natl Cancer Inst 1999;91:1908–9.[Free Full Text]

5 Robbins AS, Whittemore AS, Thom DH. Differences in socioeconomic status and survival among white and black men with prostate cancer. Am J Epidemiol 2000;151:409–16.[Abstract]

6 Cunningham J, Hankey B, Lyles B, Percy C, Ries L, Seiffert J, et al, editors. The SEER Program code manual. Revised edition. Bethesda (MD): National Cancer Institute; 1992.



             
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