Reassessing surgical guidelines for papillary thyroid cancer impact on survival: Expanding indications for lobectomy

Background: Comparisons of lobectomy versus total thyroidectomy for papillary thyroid cancer have not addressed significant threats to valid inference from observational data. The purpose of this study was to compare survival after lobectomy versus total thyroidectomy for papillary thyroid cancer while addressing bias from unmeasured confounding. Methods: This retrospective cohort study included 84,300 patients treated with lobectomy or total thyroidectomy for papillary thyroid cancer in the National Cancer Database from 2004 to 2017. The primary outcome was overall survival evaluated by flexible parametric survival models and inverse probability weighting on the propensity score. Bias from unobserved confounding was assessed using two-way deterministic sensitivity analysis and 2-stage least squares regression. Results: The median age of treated patients was 48 years (interquartile range, 37–59), 78% were women, and 76% were white. We found no statistically significant differences in overall survival or 5- and 10-year survival between patients treated with lobectomy or total thyroidectomy. Additionally, we found no statistically significant difference in survival by subgroups, including tumor size (<4 cm or ≥4 cm), age (<65 or ≥65), or estimated risk of mortality. Sensitivity analyses suggested that an unmeasured confounder would need to have an extremely large effect to change the primary finding. Conclusion: This is the first study to compare lobectomy and total thyroidectomy outcomes while adjusting for and quantifying the potential effects of unmeasured confounding variables on observational data. The findings suggest that total thyroidectomy is unlikely to offer a survival advantage over lobectomy regardless of tumor size, patient age, or overall risk of death.