Predictive Impact of Metastatic Lymph Node Burden on Distant Metastasis Across Papillary Thyroid Cancer Variants.

Background: While numerous factors determine prognosis in papillary thyroid carcinoma (PTC), distant metastasis (M1) represents one of the most dire. Escalating nodal burden and aggressive histology may contribute to higher metastatic risk, but this relationship is poorly defined and challenging to anticipate. We evaluate the predictive impact of these histological features on predicting distant metastases at initial presentation. Methods: Univariate and multivariable logistic regression models of conventional and aggressive thyroid cancer variants (well-differentiated papillary thyroid carcinoma [WDPTC], diffuse sclerosing variant [DSV], tall cell variant [TCV], poorly differentiated thyroid cancer [PDTC], and anaplastic thyroid carcinoma [ATC]) identified via U.S. cancer registry data were constructed to determine associations between M1 status and quantitative nodal burden. Associations between metastatic lymph node (LN) number and M1 disease were modeled using univariate and multivariable logistic regression with interaction terms, as well as a linear continuous probability model. Results: Overall, M1 prevalence at disease presentation was 3.6% (n = 1717). When stratified by subtype, M1 prevalence varied significantly by histology (WDPTC [1.0%], DSV [2.3%], TCV [4.1%], PDTC [17.4%], ATC [38.4%] [p < 0.001]). For WDPTC, M1 prevalence escalated with metastatic LN number (0 LN+ [0.5%], 1-5 LN+ [2.0%], 6-10 LN+ [3.4%], >10 LN+ [5.5%] [p < 0.001]) and LN ratio (p < 0.001). A statistically significant interaction was observed between histology and increasing nodal burden for M1 risk. On multivariable analysis, each successive metastatic LN conferred increased M1 risk for WDPTC (odds ratio [OR] 1.06 [1.05-1.08], p < 0.001) and TCVs (OR 1.04 [1.02-1.07], p < 0.001). In contrast, other aggressive variants had a higher baseline M1 risk, but this did not vary based on the number of positive LN (DSV, OR 1.02 [0.95-1.10], p = 0.52; PDTC, OR 1.00 [0.98-1.02], p = 0.66; ATC, 1.00 [0.98-1.02], p = 0.97). Conclusions: Progressive nodal burden independently escalates the risk of distant metastasis in WDPTC and TCVs of PTC. Conversely, aggressive variants such as PDTC and ATC have substantial M1 risk at baseline and appear to be minimally affected by metastatic nodal burden. Consideration of these factors after surgery may help tailor clinical decision-making for treatment and surveillance. Further studies are warranted to calibrate the ideal management approach for these higher risk patient groups.

Incidental parathyroidectomy in thyroidectomy and central neck dissection.

BACKGROUND: Although higher thyroidectomy volume has been linked with lower complication rates, its association with incidental parathyroidectomy remains less studied. The volume relationship is even less clear for central neck dissection, where individual parathyroid glands are at greater risk. METHODS: Patients undergoing thyroidectomy with or without central neck dissection were evaluated for incidental parathyroidectomy, hypoparathyroidism, and hypocalcemia. Univariate and multivariable analyses were performed using binary logistic regression. RESULTS: Overall, 1,114 thyroidectomies and 396 concurrent central neck dissections were performed across 7 surgeons. Incidental parathyroidectomy occurred in 22.4% of surgeries (range, 16.9%-43.6%), affecting 7.1% of parathyroids at risk (range, 5.8%-14.5%). When stratified by surgeon, lower incidental parathyroidectomy rates were associated with higher thyroidectomy volumes (R2 = 0.77, P = .008) and higher central neck dissection volumes (R2 = 0.93, P < .001). On multivariable analysis, low-volume surgeon (odds ratio 2.94, 95% confidence interval 2.06-4.19, P < .001), extrathyroidal extension (odds ratio 3.13, 95% confidence interval 1.24-7.87, P = .016), prophylactic central neck dissection (odds ratio 2.68, 95% confidence interval 1.65-4.35, P <.001), and therapeutic central neck dissection (odds ratio 4.44, 95% confidence interval 1.98-9.96, P < .001) were the most significant factors associated with incidental parathyroidectomy. In addition, incidental parathyroidectomy was associated with a higher likelihood of temporary hypoparathyroidism (odds ratio 2.79, 95% confidence interval 1.45-5.38, P = .002) and permanent hypoparathyroidism (odds ratio 4.62, 95% confidence interval 1.41-5.96, P = .025), but not permanent hypocalcemia (odds ratio 1.27, 95% confidence interval 0.48-3.35, P = .63). Higher lymph node yield in central neck dissection was not associated with higher incidental parathyroidectomy rates (odds ratio 1.13, 95% confidence interval 0.85-8.81, P = .82). CONCLUSION: Higher surgical volume conferred a lower rate of incidental parathyroidectomy. Nonetheless, greater lymph node yield in central neck dissections did not result in greater parathyroid-related morbidity. Such findings support the value of leveraging surgical volume to both optimize oncologic resection and minimize complication rates.