Disease Severity at Presentation in Patients with Disease-Related Mortality from Differentiated Thyroid Cancer: Implications for the 2015 ATA Guidelines.

Background: The current trend of less aggressive treatment of low-risk differentiated thyroid cancer (DTC) patients was recently challenged by a study reporting >10% disease-related mortality (DRM) in low-risk patients ablated with radioiodine activities below 54 mCi. However, this study and others were limited by incomplete data on disease severity at presentation. Whether patients presenting with low-risk disease are at risk for disease-related mortality is crucial for planning current treatment strategies.

Methods: Patients with documented DRM from DTC were included from the Rabin thyroid cancer registry and the Davidoff Head and Neck cancer service databases. Disease characteristics at presentation, treatments, disease course, and cause of death were analyzed.

Results: Of 1374 patients whose charts were reviewed, 56 were confirmed to have died of DTC, and 53 had sufficient data for analysis. Median time from diagnosis to death was 9 years (range 1-36). Cause of death was related to distant metastases in 46 patients and aggressive neck disease in 7 patients. The median age at diagnosis was 62 years (range 22-83, 83% older than 45), and were initially categorized as American Thyroid Association high risk in 89% of cases (in 4 cases due to high thyroglobulin levels), intermediate risk in 6% (3 older patients with N1b disease), misclassification as benign in one case, and none was low risk. Most patients had an advanced disease stage (stage IV, 88%; III, 2%; II, 2%; I, 8%). All patients with stage I disease were <45 years, with aggressive features (1 poorly differentiated, 3 gross extrathyroidal extension). One patient with stage II disease was <45 years and had distant metastases. Detection of distant metastases occurred within the first year in 25 patients and during subsequent follow-up in 25 patients. Overall, aside from one patient who was misdiagnosed as having a benign follicular adenoma at presentation, all patients had aggressive disease features at presentation.

Conclusion: None of the patients with DRM had low-risk features at presentation, supporting the current paradigm of less aggressive approach in the low-risk group. Studies analyzing mortality from thyroid cancer should stratify patients into the various risk categories based on full baseline data, including postoperative thyroglobulin levels.