Thyroid®

Proposed Risk Stratification and Patterns of Radioactive Iodine Therapy in Malignant Struma Ovarii

Introduction: Malignant struma ovarii (MSO) is a rare thyroid cancer arising within an ovarian teratoma. While surgical excision of the primary tumor is widely accepted as standard of care, recommendations for adjuvant treatment of MSO—whether or not to administer radioactive iodine (RAI)—are based largely on case reports and remain debated. In this study, we aimed to propose a risk stratification and analyze RAI utilization patterns in MSO cases. Methods: The National Cancer Database (NCDB) was queried for patients with MSO between 2004 and 2016. Demographic, oncological, and clinicopathologic data were compared between groups using Fisher's exact test. Kaplan–Meier curves were used to estimate overall survival (OS), and variables associated with OS were assessed via univariate Cox regression. We adapted the 2015 American Thyroid Association risk guidelines for MSO patients. We stratified patients into low-, intermediate-, and high-risk groups using metastasis, extraovarian extension, lymphovascular invasion, lymph node status, surgical margins, tumor size, and grade. Risk stratification, demographic, oncological, and clinicopathologic data were compared between the groups receiving and not receiving RAI therapy. We then queried the Surveillance, Epidemiology, and End Results (SEER) 18 registry for patients with MSO between 2000 and 2018 to confirm our risk stratification analysis. Results: In the NCDB analysis, a total of 158 patients were identified, and 19 received RAI. RAI therapy was associated with distant metastasis ( p  = 0.005) and lymph node status ( p  = 0.012). Twenty-one NCDB patients were stratified as high risk, and 30% of high-risk patients received RAI. High-risk stratification was associated with decreased OS via univariate Cox regression (hazard ratio = 4.0 [95% confidence interval 1.11–14.26], p  = 0.034). In our subsequent analysis using the SEER registry, there were 95 MSO patients, and 18 received RAI. Again, the majority of high-risk patients did not receive RAI, with only 41% of high-risk patients receiving RAI. Conclusions: MSO is a rare malignancy with apparently variable and inconsistent patterns of postoperative RAI administration. The risk stratification described here provides a framework to identify patients potentially at risk for mortality, and utilization of RAI in this group should be studied further.

Cancer Risks of Patients with Graves’ Disease Who Received Antithyroid Drugs as Initial Treatment: A Nationwide Population-Based Analysis

Background: Population-based studies that examine the associations between hyperthyroidism and cancer risk have yielded inconsistent results. It remains unclear whether the risks of different cancers increase in patients with Graves’ disease (GD) who received antithyroid drugs (ATDs) as initial treatment. We aimed to determine whether cancer risk increases in patients with GD, compared with controls. Methods: This nationwide retrospective cohort study utilized data from the National Health Information Database of South Korea. We included 29,502 patients aged >20 years with GD, who received ATDs as initial treatment, and 57,173 age- and sex-matched controls. The primary outcome was the incidence of various types of cancers. Hazard ratios (HRs) with confidence intervals (CIs) for cancer risk were estimated using Cox proportional hazards models. We also analyzed HR by follow-up period since the diagnosis of GD, accounting for surveillance effect. Results: The risk of biliary tract and pancreatic cancers (HR: 1.41, CI: 1.24–1.60), thyroid cancer (HR: 15.51, CI: 12.29–19.57), prostate cancer (HR: 1.48, CI: 1.28–1.71), and ovarian cancer (HR: 1.31, CI: 1.13–1.52) was elevated in the GD group than in the control group even after the first year of follow-up was excluded. The increased risk of these cancers persisted after a follow-up period of more than 5 years. The risk of thyroid cancer in patients with GD was higher during the initial follow-up period (1 to <2 years) (HR: 19.35, CI: 7.66–48.87) compared with that in the follow-up period exceeding 2 years. The cancer risk estimates remained significant after excluding patients with GD who underwent subsequent radioactive iodine therapy. Conclusion: In this large-scale population-based study, GD was associated with increased risks of biliary tract and pancreatic, prostate, ovarian, and thyroid cancers. The increased risk of thyroid cancer, particularly during the initial follow-up period, may be a surveillance effect.