Socioeconomic gradients in cancer incidence by race and ethnicity in California, 2008-2012: the influence of tobacco use or screening detectable cancers.

Purpose: There are clearly documented inequalities in cancer incidence by socioeconomic position, but it is unclear whether this is due primarily to differences in tobacco exposure and screening practices or to other factors.
Methods: Our study included 741,373 incident cases of invasive cancer from 2008 to 2012 in California. We calculated age-standardized incidence rates across twelve categories of census tract poverty as a measure of socioeconomic position (SEP) for (1) all cancer sites combined, (2) sites not strongly related to tobacco use, (3) sites not related to screening, and (4) sites not related to tobacco use or screening.
Results: There was higher cancer incidence among those living in areas with higher levels of poverty for sites not strongly related to tobacco use or screening, among Whites, Blacks, and Asians, but not among Latinos. Among Whites there was no relationship with census tract poverty at lower levels of poverty-the relationship with cancer incidence was primarily among those in higher poverty. For Blacks and Asians, there is a more linear relationship with cancer incidence across levels of poverty.
Conclusions: SEP gradients in cancer incidence remain after exclusion of cancer sites strongly related to tobacco use and screening. Our findings demonstrate a need for research on other environmental and social causes of cancer where exposures are differentially distributed by SEP.