Urban-rural differences in breast cancer incidence in Egypt (1999-2006)

Objective: To describe urban-rural differences in breast cancer incidence in Gharbiah, Egypt and to investigate if these differences could be explained by known risk factors of breast cancer. Methods: We used data from the population-based cancer registry of Gharbiah, Egypt to assess breast cancer incidence from 1999 through 2006. The Egyptian census provided data on district-specific population, age, and urban-rural classification. Incidence patterns of breast cancer by district and age-specific urban-rural differences were analyzed. Results: Overall, incidence rate of breast cancer was three to four times higher in urban areas than in rural areas (60.9/10⁵-year for urban areas versus 17.8/10⁵-year for rural areas; IRR=3.73, 95% CI=3.30, 4.22). Urban areas had consistently higher incidence of breast cancer across all age-groups for all years. Higher incidence of breast cancer was also seen in the more developed districts of Tanta and El-Mehalla. Conclusions: Higher incidence of breast cancer in urban and more developed populations might be related to higher exposure to xenoestrogens, as well as other endocrine disruptors and genotoxic substances.