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 decadesis principally attributed to small, indolent papillary thyroid cancers. A possible concomitantincrease in thyroid cancer-specific mortality remains debated.Objective: The changes in thyroid cancer incidence and incidence-based mortality were assessedusing a large population-based cohort over an 18-year period.Design & Patients: A retrospective analysis of all thyroid cancers reported in the CaliforniaCancer Registry was performed (2000-2017). Age-adjusted incidence and incidence-basedmortality 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) diagnosedwith thyroid cancer. The incidence of thyroid cancer increased across all histological subtypes(papillary, follicular, medullary, and anaplastic) and all tumor sizes. The incidence increasedfrom 6.43 to 11.13 per 100 000 person-years (average increase 4% per year; P < 0.001) over thestudy period. Thyroid cancer-specific mortality rates increased on average by 1.7% per year(P < 0.001). The increased mortality rates were greater in men (2.7% per year, P < 0.001) andpatients with larger tumors (2-4 cm) (3.4% per year, P < 0.05).Conclusions: Data from this statewide registry demonstrate that the incidence of thyroid canceris increasing, and that this phenomenon is not restricted to small papillary thyroid cancers.Rising incidence in thyroid cancers of all sizes with concurrent increase of incidence-basedmortality in men and those with larger tumors suggest a true increase in clinically significantdisease.