An international comparison of male and female breast cancer incidence rates

Abstract

Global international trends in female breast cancer incidence have been described previously but no comparable analysis of male breast cancer incidence rates has been conducted. We obtained male and female case and population data using Cancer Incidence in Five Continents (CI5). We calculated age-adjusted, sex-specific incidence rates and female-to-male incidence rate ratios (FMIRRs) and compared trends of such for the period 1988-2002. This analysis included 8,681 male breast cancer cases and 1.14 million female breast cancer cases. The highest male incidence rate was observed in Israel at 1.24 per 100,000 man-years, and the highest female incidence rate was observed in the United States at 90.7 per 100,000 woman-years. The lowest incidence rates for males (0.16) and females (18.0) were observed in Thailand. In general, male breast cancer incidence trends were variable; a minority of countries displayed evidence for an increase. In contrast, female incidence rates have been increasing in a majority of countries. The Pearson correlation coefficient (r) for male and female breast cancer incidence rates by country during 1988-2002 was 0.69. Male breast cancer rates were generally less than 1 per 100,000 man-years, in contrast to the much higher rates of female breast cancer, providing for an overall FMIRR of 122. The differences in both incidence rates and time trends between males and females may reflect sex differences in underlying risk factors, pathogenesis, and/or overdiagnosis. Conversely, the high correlation between male and female breast cancer incidences may indicate that both sexes share some common risk factors for breast cancer.

Figure 1

Trends in Sex-specific, Age-adjusted Incidence Rates for selected countries Stratified by Continent, All Ages, 1958–2002. Rates are per 100,000 woman/man years and age-adjusted to the World Standard Population. Italicized country names indicate data are regional or restricted by ethnicity.

Figure 2

Forest plot of Female-to-male Breast Cancer Incidence Rate Ratios, All Ages, 1988–2002. The grey dashed line represents the female-to-male IRR of 122 for all countries combined. Abbreviation: CI, confidence interval.

Figure 3

Correlation between Age-Adjusted Male Breast Cancer Incidence Rate and Female Breast Cancer Incidence Rate, All Ages, 1988–2002. ¹Thailand, ²India, ³Ecuador, ⁴Japan, ⁵Costa Rica, ⁶Colombia, ⁷Estonia, ⁸Slovakia, ⁹Brazil, ¹⁰Singapore, ¹¹Poland, ¹²Spain, ¹³Philippines, ¹⁴Austria, ¹⁵Switzerland, ¹⁶United Kingdom, ¹⁷Italy, ¹⁸Australia, ¹⁹Iceland, ²⁰Canada, ²¹Denmark, ²²Netherlands, ²³France, ²⁴Israel, ²⁵United States.