[Skip to Content]
[Skip to Content Landing]
Original Investigation
August 29, 2019

Explaining the Variation in Surgical Practice for Differentiated Thyroid Cancer in Ontario, Canada

Author Affiliations
  • 1Division of Cancer Care and Epidemiology, Departments of Otolaryngology and Oncology, Queen’s Cancer Research Institute, Queen’s University, Kingston, Ontario, Canada
  • 2Department of Otolaryngology/Surgical Oncology, Princess Margaret Cancer Center, Toronto, Ontario, Canada
  • 3ICES Queen’s, Queen’s University, Kingston, Ontario, Canada
JAMA Otolaryngol Head Neck Surg. 2019;145(10):949-954. doi:10.1001/jamaoto.2019.2304
Key Points

Question  What theory or concept may explain the wide variation in the surgical management of differentiated thyroid cancer?

Findings  In a population-based study of 28 754 patients with differentiated thyroid cancer in Ontario, Canada, the variation in extent of required surgical treatment was associated with the practices of high-volume surgeons in regions with the highest rates of new cases of thyroid cancer. This finding is consistent with the Enthusiasm Hypothesis, which posits that the prevalence of physicians with a preference for certain health care services leads to geographic differences in the use of those services.

Meaning  This study found that high-volume surgeons with enthusiasm for a particular treatment appeared to have a role in creating the variation in surgical practice across a large population of patients with thyroid cancer in Ontario.


Importance  In the management of differentiated thyroid cancer (DTC), the extent of surgical treatment required for most patients remains controversial and varies widely. This variation may be associated with the Enthusiasm Hypothesis, the notion that geographic differences in use of health care services are driven by the prevalence of physicians with a preference for particular services.

Objective  To evaluate the Enthusiasm Hypothesis and its applicability to the variation in the surgical treatment of thyroid cancer in Ontario, Canada.

Design, Setting, and Participants  This population-based study obtained electronic data on all health care–associated events for the complete population of insured residents of Ontario, Canada. Patients (n = 28 754) who were 18 years of age or older and underwent an initial therapeutic thyroid surgical procedure for a papillary or follicular carcinoma diagnosis between January 1, 2000, and December 31, 2015, were included. The final data analysis was performed January 31, 2019.

Exposures  Therapeutic thyroid cancer surgical procedure.

Main Outcomes and Measures  Numbers of surgeons, extent of surgical treatment, and case volumes in 14 geographic regions in Ontario.

Results  In total, 28 754 patients with DTC were included, of whom 22 600 (78.6%) were female, with a mean (SD) age of 49 (14) years. The use of total thyroidectomy for DTC varied widely across geographic regions of Ontario, from 45.8% to 77.1% of all cancer cases. More than 90% of the overall variation in practice (total thyroidectomy vs less-than-total thyroidectomy) could be explained by the practices of the high-volume surgeons (enthusiasts) in regions with the highest rates of thyroid cancer diagnosis.

Conclusions and Relevance  The Enthusiasm Hypothesis appears to be consistent with the findings of this study. The practices of the high-volume surgeons who were enthusiastic for total thyroidectomy in the geographic regions with the highest rates of thyroid cancer diagnosis may account for the variation in practice across Ontario between 2000 and 2015.