Stats Canada: If you're poor, risk for breast cancer is increased

Breast cancer incidence and neighbourhood income
By Marilyn J. Borugian et al.

Incidence and mortality rates for most chronic diseases including several types of cancer are higher among people of lower socio-economic status. By contrast, for female breast cancer in developed countries, the relationship may be inverted, with women of higher socio-economic status having higher rates, even when risk factors that differ by socio-economic status such as parity, age at first birth and hormone use are taken into account. Only one earlier study examined the risk of breast cancer in relation to socio-economic status in Canada, and it focused on the effects of passive smoking.