Rising Incidence and Incidence-Based Mortality of Thyroid Cancer in California, 2000-2017

Abstract Context The increased incidence of thyroid cancer globally over the past several decades is principally attributed to small, indolent papillary thyroid cancers. A possible concomitant increase in thyroid cancer-specific mortality remains debated. Objective The changes in thyroid cancer incidence and incidence-based mortality were assessed using a large population-based cohort over an 18-year period. Design & Patients A retrospective analysis of all thyroid cancers reported in the California Cancer Registry was performed (2000–2017). Age-adjusted incidence and incidence-based mortality rates were analyzed using a log-linear model to estimate annual percent change. Results We identified 69 684 individuals (76% female, median age 50 years) diagnosed with thyroid cancer. The incidence of thyroid cancer increased across all histological subtypes (papillary, follicular, medullary, and anaplastic) and all tumor sizes. The incidence increased from 6.43 to 11.13 per 100 000 person-years (average increase 4% per year; P