Postoperative Radioiodine Treatment within 9 Months from Diagnosis Significantly Reduces the Risk of Relapse in Low-Risk Differentiated Thyroid Carcinoma.

PURPOSE

Although postoperative radioiodine (RAI) therapy has been used in patients with differentiated thyroid carcinoma (DTC) for many years, there is still lack of data defining the timing of RAI administration. A retrospective analysis was carried out to answer the question whether the time of postoperative RAI treatment demonstrated any impact on long-term outcomes, particularly in low-risk DTC.

MATERIAL

The analyzed group involved 701 DTC patients staged pT-TN-NM, who underwent total thyroidectomy and postoperative RAI therapy. According to the time interval between DTC diagnosis and RAI administration, patients were allocated to one of three groups: up to 9 months ( = 150), between 9 and 24 months ( = 323), and > 24 months ( = 228). Median follow-up was 12.1 years (1.5-15.2).

RESULTS

Based on an initial DTC advancement and postoperative stimulated thyroglobulin concentration patients were stratified as a low-, intermediate-, and high-risk group. Low-risk patients, who received RAI therapy up to 9 months, demonstrated significantly lower risk of relapse comparing to those, in whom RAI was administered between 9 and 24 months and after 24 months since DTC diagnosis: 0%, 5.5%, and 7.1%, respectively. Regarding intermediate- and high-risk groups, the differences in the timing of postoperative RAI treatment were not significant.

CONCLUSION

If postoperative RAI treatment is considered in low-risk DTC, any delay in RAI administration above 9 months since diagnosis may be related to poorer long-term outcomes.