Increased rates of advanced thyroid cancer in California

We have noted an unusually high rate of advanced thyroid cancers presenting from across California. We examined the rates of thyroid cancer presentation throughout California for potential geographic clustering.

A total of 26,983 patients with a new diagnosis of thyroid cancer (1999-2008) were abstracted from the California Cancer Registry and the Office of Statewide Health Planning and Development registry. Percentages of advanced thyroid cancer rates were calculated within each county (defined as those with distant metastatic stage; regional and/or distant metastatic stage [RM]) as well as those with well-differentiated thyroid cancer diagnosed before age 30. National averages were taken from Surveillance, Epidemiology, and End Results (SEER) data.

There was no obvious clustering of advanced cases within certain regions in California; however, on average, the entire state of California had significantly higher rates of distant metastatic thyroid cancer (6.73%) and RM (34.92%) than the national SEER averages (4%, 29%, respectively, P < 0.001). Of the 47 California counties, 20 had significantly higher percentages of distant metastatic thyroid cancer than the national SEER average (range, 6%-13% versus 4%, P < 0.05), and 20 had a higher percentage of RM than the national SEER average (range, 35%-48% versus 29%, P < 0.05). Two California counties had higher rates of young patients with well-differentiated thyroid cancer (range, 14.29%-17.9%) than the national SEER average (12%).

California exhibits more advanced thyroid cancers than the national SEER population average. Further studies are warranted to better understand etiologies for these disparities, which may include environmental impacts and/or delays in diagnosis.