The incidence of female breast and genital cancer: analysis of the age-dependence.

Worldwide age-incidence patterns for female breast and genital cancers were normalized for differences in frequency of tumor occurrence and compared. The percentage of total cancer incidence which occurred in elderly subjects differed between populations but was similar for cancer of the breast, ovary, and corpus uteri within a given population. In addition, cancers of the breast, ovary, and corpus uteri exhibited similar ranges of distribution about the worldwide median incidence at all age intervals and strong positive correlations between crude incidence rates in the populations studied. Despite these and other similarities, breast cancer exhibited a correlation between crude incidence rate and percentage of total incidence which occurred in elderly subjects which was not apparent in the genital cancers. We cannot exclude the possibility that this correlation is coincidental. However the possibility of identifying factors predisposing to or protecting against breast cancer is attractive. The results of this study suggest that such factors would apply to breast but not to genital tissue.