Adjuvant radioactive iodine therapy is associated with improved survival for patients with intermediate-risk papillary thyroid cancer.

Abstract

Papillary thyroid cancer (PTC) is the most common endocrine malignancy. The long-term prognosis is generally excellent. Due to a paucity of data, debate exists regarding the benefit of adjuvant radioactive iodine therapy (RAI) for intermediate-risk patients. The objective of the study was to examine the impact of RAI on overall survival in intermediate-risk PTC patients. Adult patients with intermediate-risk PTC who underwent total thyroidectomy with/without RAI in the National Cancer Database, 1998-2006, participated in the study. Intermediate-risk patients, as defined by American Thyroid Association risk and American Joint Commission on Cancer disease stage T3, N0, M0 or Mx, and T1-3, N1, M0, or Mx were included in the study. Patients with aggressive variants and multiple primaries were excluded. Overall survival (OS) for patients treated with and without RAI using univariate and multivariate regression analyses was measured. A total of 21 870 patients were included; 15 418 (70.5%) received RAI and 6452 (29.5%) did not. Mean follow-up was 6 years, with the longest follow-up of 14 years. In an unadjusted analysis, RAI was associated with improved OS in all patients (P < .001) as well as in a subgroup analysis among patients younger than 45 years (n = 12 612, P = .002) and 65 years old and older (median OS 140 vs 128 mo, n = 2122, P = .008). After a multivariate adjustment for demographic and clinical factors, RAI was associated with a 29% reduction in the risk of death, with a hazard risk 0.71 (95% confidence interval 0.62-0.82, P < .001). For age younger than 45 years, RAI was associated with a 36% reduction in risk of death, with a hazard risk 0.64 (95% confidence interval 0.45- 0.92, P = .016). This is the first nationally representative study of intermediate-risk PTC patients and RAI therapy demonstrating an association of RAI with improved overall survival. We recommend that this patient group should be considered for RAI therapy.