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

CONTEXT: 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.

OBJECTIVE: The objective of the study was to examine the impact of RAI on overall survival in intermediate-risk PTC patients.

DESIGN/SETTING: Adult patients with intermediate-risk PTC who underwent total thyroidectomy with/without RAI in the National Cancer Database, 1998-2006, participated in the study.

PATIENTS: 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.

MAIN OUTCOME MEASURES: Overall survival (OS) for patients treated with and without RAI using univariate and multivariate regression analyses was measured.

RESULTS: 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).

CONCLUSION: 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.