The purpose of this study was to evaluate two competing hypotheses regarding the survival disadvantage for black men with prostate cancer. The first hypothesis (biologic) predicts that black men with prostate cancer present with a less favorable tumor stage and grade than white patients. The second hypothesis (access) predicts that racial differences in stage and grade at presentation will be smaller in populations where blacks and whites have equal access to treatment than in the general population.

The subjects for this study were black and white patients with incidence prostate cancer who were in the San Francisco Bay Area SEER Program registry and were over 35 year of age. Some (about 25%) were members of San Francisco Bay Area's Kaiser Permanente. Patients who were members of Kaiser were considered to have equal access to treatment.

Black men were more likely to be diagnosed at a later stage, to have more severe tumor grades, and to have substantially poorer survival after diagnosis. This was true for both Kaiser members and non-members. Among Kaiser members, 21.9% of blacks versus 15.7% of whites were diagnosed at a distant stage, and a smaller proportion had tumors that were well differentiated. Among nonmembers, 20.3% of blacks versus 13.1% of whites were diagnosed at a distant stage, and a smaller proportion had tumors that were moderately differentiated. The death rate ratio (adjusted for stage and age) for blacks compared with whites was similar for Kaiser members and non-members (1.28 and 1.22 respectively). It appears that the effect of race on mortality only held for patients who were Kaiser members, and the death rate ratio for non-members was not statistically significant. Further analyses would be needed to confirm this finding.

There also appeared to be racially distinct patterns of treatment. Among Kaiser members with localized stage cancers, there was a tendency for black men to receive surgery or radiation therapy more frequently than white men. Among Kaiser members with regional/distant stage cancers, there was a tendency for white men to receive these therapies more than black men. There were no consistent treatment patterns observed among non-members.

The authors conclude that the data supported the hypothesis of increased tumor virulence in black men. It would be useful to directly assess access to treatment within Kaiser before accepting this hypothesis definitively.