Breast cancer mortality and associated factors in São Paulo State, Brazil: an ecological analysis.

OBJECTIVE: Identify the factors associated with the age-standardised breast cancer mortality rate in the municipalities of State of São Paulo (SSP), Brazil, in the period from 2006 to 2012.

DESIGN: Ecological study of the breast cancer mortality rate standardised by age, as the dependent variable, having each of the 645 municipalities in the SSP as the unit of analysis.

SETTINGS: The female resident population aged 15 years or older, by age group and municipality, in 2009 (mid-term), obtained from public dataset (Informatics Department of the Unified Health System).

PARTICIPANTS: Women 15 years or older who died of breast cancer in the SSP were selected for the calculation of the breast cancer mortality rate, according to the municipality and age group, from 2006 to 2012.

MAIN OUTCOME MEASURES: Mortality rates for each municipality calculated by the direct standardisation method, using the age structure of the population of SSP in 2009 as the standard.

RESULTS: In the final linear regression model, breast cancer mortality, in the municipal level, was directly associated with rates of nulliparity (p<0.0001), mammography (p<0.0001) and private healthcare (p=0.006).

CONCLUSIONS: The findings that mammography ratio was associated, in the municipal level, with increased mortality add to the evidence of a probable overestimation of benefits and underestimation of risks associated with this form of screening. The same paradoxical trend of increased mortality with screening was found in recent individual-level studies, indicating the need to expand informed choice for patients, primary prevention actions and individualised screening. Additional studies should be conducted to explore if there is a causality link in this association.