Risk of thyroid as a first or second primary cancer. A population-based study in Italy, 1998–2012

Abstract Background The number of patients living after a cancer diagnosis is increasing, especially after thyroid cancer (TC). This study aims at evaluating both the risk of a second primary cancer (SPC) in TC patients and the risk of TC as a SPC. Methods We analyzed two population‐based cohorts of individuals with TC or other neoplasms diagnosed between 1998 and 2012, in 28 Italian areas covered by population‐based cancer registries. Standardized incidence ratios (SIRs) of SPC were stratified by sex, age, and time since first cancer. Results A total of 38,535 TC patients and 1,329,624 patients with other primary cancers were included. The overall SIR was 1.16 (95% CI: 1.12–1.21) for SPC i…