Introduction: Papillary cancer is the most common neoplasm of the thyroid. The mainstay of treatment is thyroidectomy, but most patients are additionally treated with radioactive iodine (RAI). Its utility is controversial. This study seeks to determine whether RAI use affects patient outcome and to identify specific cohorts of patients that benefit from its use.
Methods: The Surveillance, Epidemiology, and End Results (SEER) database is a large-scale sample of approximately 14% of the US population. It was used to identify patients with papillary carcinoma of the thyroid. Statistical analyses were used to compare prognostic factors such as lymph node status, age, tumor size, and treatment with RAI.
Results: A total of 14,545 patients were identified in SEER as having papillary cancer of the thyroid. Multivariate analysis showed significantly worse outcome in patients with age>45 years, tumor size >2 cm, lymph node disease, and distant metastases. Multivariate analysis failed to show RAI significantly affecting mortality. Survival between those not treated with RAI was similar to those whose treatment included it (P = 0.9176). Subgroup analysis identified patients older than 45 years with primary tumors >2 cm and disease in the lymph nodes with distant metastatic disease as the only group positively affected by RAI.
Conclusions: Despite its widespread use in the treatment of well-differentiated papillary cancer of the thyroid, RAI only affects a survival advantage in older patients with large primary tumors involving the lymph nodes and with distant spread. Treating other patient groups is costly and offers no improvement in outcome.
Copyright 2007 Wiley-Liss, Inc.