Radioactive iodine treatment for node negative papillary thyroid cancer with capsular invasion only: Results of a large retrospective study

Aim: With thyroid carcinoma the decision to use radioactive iodine (RAI) ablation depends on the risk of poor outcomes. Although extrathyroid extension (ETE) is well known as a risk of poor outcomes for papillary thyroid carcinoma (PTC), the definition of minimal ETE is too broad, as it encompasses both microscopic invasion of the thyroid capsule (capsular invasion [CI]) and macroscopic invasion of the sternothyroid muscle. Methods: We conducted a retrospective study to analyze the prognostic benefit of RAI ablation according to the presence of CI in a consecutive series of patients with PTC between October 1997 and December 2008. We studied two groups of patients, including those who received RAI (group I, n=121) and those who did not (group II, n=108). During follow-up, we assessed the locoregional recurrence of all patients. Results: There were no statistically significant difference between the groups regarding locoregional recurrence at follow-up (13.2% for group Ivs 9.3% for group II, P=0.441). The association between RAI and locoregional recurrence in PTC patients with CI remained insignificant after adjusting for potential confounders, such as age, tumor size, sex, lymphatic invasion, vascular invasion and tumor multiplicity (P=0.409, hazard ratio=0.698, 95% confidence interval, 0.298-1.639). Conclusions: This retrospective study suggests that RAI treatment is not associated with less locoregional recurrence in PTC patients who only demonstrate CI, although further prospective studies are required to confirm these findings.