We found a significant interaction between race and tumor aggressiveness for the initial treatment of clinically localized prostate cancer in a population-based cohort of African-American and non-Hispanic white men. Among patients with clinically more aggressive cancers, defined by elevated PSA levels and/or Gleason scores, African Americans were significantly less likely to undergo radical prostatectomy and significantly more likely to receive conservative management. However, the majority of study subjects (71.1%) had less aggressive cancers, and we found no significant racial differences in treatment for this group. Although African Americans were slightly more likely to receive conservative management, the proportions of men undergoing radical prostatectomy were essentially identical.
We considered a number of explanations for the racial differences in treating the clinically more aggressive cancers. In general, African Americans have more aggressive cancers than non-Hispanic whites and are more likely to present with advanced-stage disease.1,2
Men with a clinically localized cancer but elevated PSA levels and/or high Gleason scores are at increased risk of having a pathologically advanced cancer,22
and radical prostatectomy is unlikely to be curative for these patients.25
Among men with more aggressive cancers, we found no racial differences in undergoing bone scans, which would detect metastatic disease. However, physicians may have empirically treated these African-American subjects as being more likely to have clinically advanced-stage disease by withholding radical prostatectomy and offering either conservative management or radiation therapy. This explanation is plausible because African Americans with more aggressive cancers were more likely to be treated conservatively (38.9% vs 16.3%), though they were slightly less likely to receive radiation therapy (25.9% vs 31.7%).
African Americans with more aggressive cancers may also have been in poorer health than non-Hispanic whites. Although adjusting for comorbidity did not explain away the racial differences in treatment, African Americans were significantly more likely to report multiple comorbid conditions. Our measure of comorbidity may not have captured baseline health and disease severity accurately enough to account for treatment differences.
Physicians also have an obvious role in influencing treatment selection. In a study of North Carolina men with prostate cancer, Demark-Wahnefried et al. found few racial differences regarding types of treatment discussed with physicians or in receiving aggressive treatment.26
Furthermore, the physician's recommendation was the most important determinant of treatment selection. Although we found no racial differences in discussing radical prostatectomy and radiation therapy among men with more aggressive cancers (data not shown), physicians may have been less likely to recommend aggressive treatment for African-American subjects if they believed them to be at increased risk for poor outcomes. Such judgments may have been based on the physician's perception of comorbidity or psychosocial conditions that we did not capture with our survey instrument. Another possibility is that aggressive treatments were recommended, but the content or the quality of the discussion dissuaded African Americans from these treatments. We do not know whether the patients fully understood their treatment options or how they weighed the uncertainties of disease prevention against known treatment complications.
We found no racial differences in treating prostate cancer for the majority of the PCOS subjects—those with less aggressive disease. Most importantly, essentially equal proportions of African Americans and non-Hispanic whites underwent radical prostatectomy in both the unadjusted and adjusted analyses. Although some previous studies have reported similar findings,4,26–28
they were limited either by having small sample sizes, by not adjusting results for comorbidity or tumor aggressiveness, or by excluding men pathologically upstaged after radical prostatectomy. Most studies consistently showed that African Americans were less likely than non-Hispanic whites to receive aggressive treatment, particularly radical prostatectomy, for early stage prostate cancer.11–13,29–33
The conflicting results may be explained by secular trends in diagnosing prostate cancer. Many cases in the previous reports were diagnosed before PSA testing was available.11–13,29,33–35
Nearly three quarters of the conservatively treated men in the study by Schapira et al.12
were diagnosed following transurethral resection of the prostate (TURP), as were more than a third of the patients evaluated by Klabunde et al.13
Men with a screening-detected cancer are probably more likely to consider aggressive treatment than those with incidental cancers, as evidenced by the increasing rate of radical prostatectomy and radiation following the introduction of PSA.9,10
Another reason for the conflicting results was that we evaluated only subjects with clinically localized cancer. The largest previous studies used SEER data, which assign cancer stage using clinical and pathological data.11–13
The SEER staging will classify a man with clinically localized cancer who is upstaged following radical prostatectomy as having regional stage disease. Although Schapira et al. adjusted for SEER staging by reclassifying advanced cases with radical prostatectomy and lymphadenectomy as localized, other analyses combined local and regional cancers.11,13,36,37
Because radical prostatectomy is generally reserved for local stage cancer, the racial differences seen in the combined analyses may reflect African Americans’ greater likelihood for presenting with more aggressive and advanced stage cancers.
The finding that racial differences in undergoing radical prostatectomy appear to be decreasing with time raises another issue—are African Americans now receiving better care? Racial disparities have been reported for other cancers,38,39
end-stage renal disease,40,41
and coronary reperfusion,42
where African Americans were shown to be receiving less than optimal care. With clinically localized prostate cancer, though, there is less certainty about the benefits of aggressive treatment.43
The first randomized trial demonstrating a benefit for radical prostatectomy compared to watchful waiting was just published in September, 2002.44
Although prostate cancer deaths were significantly decreased in this Scandinavian trial, there was no significant difference for overall survival. No similar studies have been published for radiation therapy. Even though we found no racial differences for undergoing radical prostatectomy, African Americans were still slightly more likely to be managed conservatively. Given the known risks and uncertain benefits of aggressive treatment for clinically localized disease, this may be an appropriate decision.
Our analyses have some potential limitations. Baseline data on symptoms and function were obtained up to 6 months after the time of diagnosis and could be affected by recall bias. However, a validation study of the Prostate Cancer Outcomes Study showed reasonably high agreement between baseline and 6-month estimates of prediagnostic function.45
Selection bias could be introduced by the nonresponders. In our restricted analysis, where subject eligibility was based on age, race, stage, and geographic area, 14.6% of eligible subjects did not respond. However, there were no significant differences between the responders and the nonresponders for age, race, stage, grade, or initial treatment. Finally, we may have misclassified initial treatment because treatment assignments were based on data from medical record abstractions completed within 6 months of diagnosis. We found, though, that the racial patterns for treatment persisted when we used self-reported data to obtain follow-up through 24 months after diagnosis.
We conclude that the African Americans in PCOS with more aggressive cancers were less likely than non-Hispanic whites to undergo radical prostatectomy, but more likely to undergo conservative management. This disparity may reflect African Americans’ greater risk for presenting with pathologically advanced cancer and/or their values regarding the risks and benefits of surgical treatment. Comorbidity and conventional socioeconomic factors could not explain treatment differences, though more sensitive measures may be needed. Among the majority of subjects—those with less aggressive cancers—there were no significant treatment differences by race. Although the African Americans were slightly more likely to receive conservative management, the proportions of men undergoing radical prostatectomy were essentially identical. Further research should evaluate the content and quality of treatment discussions as well as patient preferences regarding the risks and benefits of aggressive treatment.