Renal cancer paradox: higher incidence but not higher mortality among African-Americans.

To compare temporal trends in the incidence and mortality of renal cell cancer among blacks and whites for clues to etiologic differences. We examined trends in age-adjusted and age-specific Surveillance Epidemiology and End Results incidence and US mortality rates for renal cancer for 1973 through 2007, as well as nephrectomy rates from surgery codes for kidney cancer for 2000 through 2007. For nearly four decades, incidence rates for renal cell cancer have been rising more rapidly among blacks than whites, leading to a shift in excess from among whites to among blacks, almost entirely accounted for by an excess of localized disease. The incidence patterns are puzzling, as localized renal cell cancer is primarily detected incidentally by imaging, to which blacks have historically had less access. In contrast to the incidence patterns, there has been an unexpected convergence of renal cancer mortality rates, which have been virtually identical among blacks and whites since the early 1990 s. Nephrectomy rates, regardless of stage, were lower among blacks than among whites, despite almost identical cause-specific survival rates in both races. The identical mortality patterns, combined with higher and more rapidly increasing incidence and lower rates of nephrectomies among blacks, suggest that renal cell cancer may tend to be a less aggressive tumor in blacks. This hypothesis is supported by the favorable stage distribution among blacks and their higher survival for distant and unstaged cancer. Further research into the enigmatic descriptive epidemiology and the biology and natural history of renal cell cancer may shed light on the etiology of this malignancy and its more frequent occurrence among black Americans.