Ethnic variation in breast cancer survival: a review.

Intercountry, as well as intracountry, survival comparisons have revealed some differences in breast cancer survival among various ethnic populations. Most of these differences are probably explained by factors related to socioeconomic status. However, the well documented survival advantage of Japanese patients compared to Caucasian patients remains unexplained. Some recent studies suggest an adverse prognostic effect for obesity. Although still inconclusive, these findings raise the possibility that the better survival of Japanese patients may be in part related to their lower mean body weight. An effect of the lower fat intake of the Japanese in explaining their breast cancer survival advantage has little support at present, but, like the obesity hypothesis, deserves further study.