Timing of Radioactive Iodine Administration Does Not Impact the Outcomes in Differentiated Thyroid Cancer Patients

Program: Abstracts - Orals, Poster Previews, and Posters
Session: SAT 270-310-Thyroid Neoplasia (posters)
Saturday, April 2, 2016: 1:15 PM-3:15 PM
Exhibit/Poster Hall (BCEC)

Poster Board SAT 303
Rafael Selbach Scheffel*1, Andre Borsatto Zanella2, Jose Miguel S Dora3 and Ana Luiza Maia4
1Hospital de ClĂ­nicas de Porto Alegre, Porto Alegre, Brazil, 2Hospital de Clinicas de Porto Alegre, Porto Alegre, Brazil, 3Hospital de Clinicas de Porto Alegre, Porto Alegre RS, Brazil, 4Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
Background: Radioactive iodine (RAI) therapy is widely used on the management of differentiated thyroid cancer (DTC). Nevertheless, the impact of the time interval between total thyroidectomy (TT) and RAI administration on clinical outcomes in DTC remains a matter of discussion.

Methods: DTC patients who underwent TT, received RAI therapy and had disease status after the initial therapy available were included. Patients were allocated in two groups, according to the time interval between TT and RAI, less than 6 months after TT (Group A) or more than 6 months (Group B). Disease-free was defined as no clinical, imaging or biochemical evidence of tumors. 

Results: From a cohort of 901 DTC patients, 545 individuals were included. Of them, 436 (80.0%) were women and 464 (85.1%) had papillary thyroid carcinoma. The TNM stage were as follow: 322 (59.1%) patients were in stage I, 62 (11.4%) in stage II, 65 (11.9%) in stage III and 82 (15.0%) in stage IV. The median time interval between TT and RAI was 6 months (interquartile range - IQR 7). Two-hundred-ninety-five patients were allocated in group A and 250 in group B. The median time interval between TT and RAI in Group A was 3 (IQR 3) and in group B was 10.5 (IQR 8) months. There were no differences on gender, histological type, tumor size, distant metastasis or TNM status (all P>0.10) between groups. Patients in group B were older (47.1 vs. 43.1 years P = 0.02), had less cervical metastasis (73.6% classified as N0 vs. 59.3%, P=0.002) and were more commonly classified as low ATA risk (48.0 vs. 36.6% P = 0.027). In the first year after initial therapy, 59.3% and 65.6% of patients in groups A and B, respectively, were considered disease free (P = 0.15). Of note, the percentage of patients classified as disease free was similar even when analyzing the subgroup of high risk patients (n=71, 9.5% vs. 10.0%, P=1.0). These figures do not change after a median of follow-up of 6 (IQR 6) years. In the multiple logistic regression the time interval between TT and RAI was not associated with persistent disease status (RR 0.97 95%CI 0.80-1.19).

Conclusions: Timing of RAI does not seem to interfere on the clinical outcomes in DTC and, therefore, can be safely planned taking into account patient and health system factors.

Nothing to Disclose: RSS, ABZ, JMSD, ALM

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