More than meets the size: Evaluating guideline impact on extent of surgery for follicular thyroid carcinoma

The comparison of mean proportions of lobectomy pre- and post- ATA guidelines as in this study by Cogua et al. gives a crude result susceptible to outlier years, implementation lag time, and confounding by other simultaneous policy change and other clinical factors.2 One key example of a concomitant policy event during the study period is Medicaid expansion. Previous studies have found Medicaid expansion to be associated with increased diagnosis of DTCs,8 but Medicaid insurance coverage has also been associated with inappropriate use of thyroid lobectomy.9 Other approaches to analysis including interrupted time-series and difference-in-differences (for comparative studies) can overcome these issues and provide granularity to data which is by its nature complex and variable with respect to many factors not measured in the SEER database.10 While individual clinical and pathologic factors weigh strongly on individual decision making for extent of thyroidectomy in follicular thyroid carcinomas, the impact of the 2015 ATA guidelines cannot be overstated and represent a paradigm shift in the way thyroid cancers are approached surgically. Future study of clinical guidelines in thyroid cancer will benefit from careful consideration of important clinical characteristics and outcomes beyond just tumor size with an eye toward analysis strategy that accounts for the complexities and confounding events inherent to these data.