Cancers of the breast, endometrium and ovary: geographic correlations.

Patterns of incidence of breast, endometrial and ovarian cancer show strong similarities in both international and inter-regional comparisons, similarities readily confirmed by the calculation of coefficients of correlation. Migrant studies suggest that environmental factors are more important than genetic differences between populations. Correlation studies have shown that dietary factors can explain much of the international variation, and most suspicion has fallen on dietary fat. Differences in fertility between populations also correlate with the variations in incidence. For breast cancer, the latter may be an important determinant of variation within countries in the pre-menopausal age group, with dietary differences accounting for variations in post-menopausal rates internationally. There is scope for improving upon earlier studies, and for investigating the relative contributions of diet and fertility to the geographic patterns of endometrial and ovarian cancers.