Thyroid Cancer Incidence and Mortality by Socioeconomic Level in the State of São Paulo, Brazil 2001-2017

Thyroid cancer is rising largely due to greater detection of indolent or slow-growing tumors; we sought to compare the incidence and mortality profiles of thyroid cancer in the State of São Paulo by socioeconomic status (SES).

Data on thyroid cancer cases diagnosed from 2003 to 2017 in the Barretos Region and from 2001 to 2015 in the municipality of São Paulo were obtained from the respective cancer registries. Corresponding death data were obtained from a Brazilian public government database. Age-standardized rates were calculated and presented as thematic maps. The rates were also calculated by SES and spatial autocorrelation was assessed by global and local indices.

There were 419 cases of thyroid cancer and 21 deaths in Barretos, contrasting with the highly populated São Paulo, with 30 489 cases and 673 deaths. The overall incidence rates in São Paulo (15.9) were three times higher than in Barretos (5.7), while incidence rates in women were close to five times higher in Barretos and four times higher in São Paulo than in men. Mortality rates were, in relative terms, very low in both regions. A clear stepwise gradient of increasing thyroid cancer incidence with increasing SES was observed in São Paulo, with rates in very high SES districts four times those of low SES (31.6 vs 8.1). In contrast, the incidence rates in Barretos presented little variation across SES levels.

Thyroid cancer incidence varied markedly by SES in São Paulo, with incidence rates rising with increasing socioeconomic index. Overdiagnosis is likely to account for a large proportion of the thyroid cancer burden in the capital.