Relation between surgical oncologic quality indicators for papillary thyroid cancer.

BACKGROUND: It remains unclear how thyroid surgical oncologic quality indicators (TSOQIs) are related to each other, and how to best interpret and apply these measures within the context of surgical quality assurance. We aimed to examine the relation between 3 TSOQIs: postoperative serum thyroglobulin level, 24-hour radioactive iodine uptake (RAIU) and metastatic lymph node ratio (MLNR). METHODS: We conducted a retrospective review of patients who underwent total thyroidectomy for treatment of papillary thyroid cancer (PTC) performed by a single high-volume thyroid surgeon at a tertiary referral centre between 2012 and 2017. To establish the strength of correlation between pairs of quality indicators and the MACIS (metastasis, age, completeness of resection, invasion and size) prognostic score, we performed tests of normality and used the Spearman correlation coefficient to determine the correlation of nonnormal data containing outliers. RESULTS: A total of 139 patients with PTC were included in the study. Their mean MACIS score was 5.0 (standard deviation 1.5). Fifteen patients had high-risk thyroid cancer (MACIS score > 6.99). A weak correlation was found between serum thyroglobulin level and RAIU (r s = 0.27, p = 0.006) and a moderate correlation was found between serum thyroglobulin level and MLNR (r s = 0.40 p = 0.002). A weak correlation between serum thyroglobulin level and MACIS score was also observed (r s = 0.20, p = 0.05). CONCLUSION: Based on our findings, we propose that the postoperative serum thyroglobulin level represents the quality metric that has the most clinical utility because it is measurable in all patients and also correlates with both RAIU and MLNR. With further research, surgeons seeking to evaluate the oncologic quality of thyroidectomy performed for PTC may consider applying a quality indicator to their future practice.