Delayed initial radioactive iodine therapy resulted in poor survival in patients with metastatic differentiated thyroid carcinoma: a retrospective statistical analysis of 198 cases.

UNLABELLED To elucidate the prognostic role of (131)I radioactive iodine therapy (RIT), we conducted a retrospective cohort study analyzing the clinical factors that affect survival of postoperative patients with differentiated thyroid carcinoma (DTC). METHODS We included 198 DTC patients with extrathyroidal extension who received total or near-total thyroidectomy and then RIT in our hospital from January 1997 to June 2009: patients with lymph node metastases only (n = 47), lung metastases without bone metastases (n = 105), or bone metastases and other distant metastases (lung, liver, brain, and skin) (n = 46). Hemithyroidectomy or subtotal thyroidectomy had been performed before total or near-total thyroidectomy in 59 patients. Disease-specific survival after initial RIT was statistically evaluated using relevant clinical parameters, including age at initial RIT, pathology, sex, therapeutic history before initial RIT, pre- and posttherapeutic serum thyroglobulin ("prethyroglobulin" and "postthyroglobulin," respectively) at initial RIT, thyroglobulin under thyroid-stimulating hormone stimulation at initial RIT ("peak thyroglobulin"), grade of uptake at scintigraphy, extent of metastasis, and number of total RITs. RESULTS During follow-up after initial RIT (average, 5.37 y), 24 patients died from DTC (11 male patients and 13 female). The most common reasons for death were respiratory failure due to lung metastases (n = 11) and uncontrollable brain metastases (n = 6). Univariate analysis showed that disease-specific survival was related to the following factors: extent of metastasis, age at initial RIT (<45 y), prethyroglobulin (<125 ng/mL), peak thyroglobulin (<1,000 ng/mL), and interval from total thyroidectomy to initial RIT (<180 d). A past history of hemithyroidectomy or subtotal thyroidectomy was not related to disease-specific survival. Multivariate analysis showed 3 factors to be independent prognostic factors--grade of (131)I uptake at whole-body scintigraphy, extent of metastasis, and interval to RIT (P ≤ 0.001, 0.010, and 0.005, respectively)--and also showed that risk of death in patients with an interval over 180 d was 4.22 times higher than in those with an interval within 180 d. Kaplan-Meier analysis revealed that a shorter interval (180, 365, or 1,000 d) had prognostic value even in the subgroups 45 y or older, with lung metastases, and with bone metastases or more. CONCLUSION The present study suggests that delaying initial RIT until more than 180 d after total thyroidectomy may result in poor survival for DTC patients.