Radioactive iodine does not improve overall survival for patients with aggressive variants of papillary thyroid carcinoma less than 2 cm

Abstract

Background: Tall cell and diffuse sclerosing variants of papillary thyroid cancer are associated with aggressive features. Radioactive iodine after total thyroidectomy is poorly studied.

Methods: Patients ≥18 years in the National Cancer Data Base from 2004 to 2016 with classic papillary thyroid cancer, tall cell, or diffuse sclerosing 1 mm to 40 mm were identified. Logistic regression identified factors associated with aggressive features. Overall survival was assessed using Kaplan-Meier method and log-rank tests, after propensity score matching for clinicopathological and treatment variables.

Results: A total of 155,940 classic papillary thyroid cancer patients, 4,011 tall cell, and 507 diffuse sclerosing were identified. Tall cell patients represented an increasing proportion of the study population during the analysis period, whereas diffuse sclerosing and classic papillary thyroid cancer patients showed a statistically significant decline. Extrathyroidal extension and nodal involvement were more prevalent among tall cell and diffuse sclerosing patients when compared to those diagnosed with classic papillary thyroid cancer (P < .01). Adjuvant radioactive iodine was less frequently used in patients with classic papillary thyroid cancer when compared to tall cell and diffuse sclerosing patients (42.6% vs 62.4%, 59.0%; P < .001, respectively). Aggressive variants receiving total thyroidectomy versus total thyroidectomy + radioactive iodine propensity score matched across clinicopathologic variables were analyzed. There was no difference in overall survival between the 2 treatment groups for tumors <2 cm (01-1.0 cm, 92.2% vs 84.8%; P = .98); (1.0-2.0 cm, 72.7% vs 88.1%; P = .82). However, overall survival was improved for total thyroidectomy + radioactive iodine propensity score matched patients with tumor sizes 21 to 40 mm versus total thyroidectomy (83.4% vs 70.0%, P = .004).

Conclusion: For aggressive tumor variants ≤2 cm treated with total thyroidectomy, there is no overall survival advantage provided by the addition of adjuvant radioactive iodine.