Data on Repeated (131)I-WB Scans and the Incidence of Positive Tg and Negative (131)I-WBS in DTC Patients from a 24 Months Study

We present data on repeated iodine-131 whole body scans ((131)I-WBS) in differentiated thyroid cancer patients (DTC) after surgery and (131)I remnant ablation and on increased thyroglobulin (Tg) with negative (131)I-WBS, in a retrospective study at our hospital. A total of 106 patients (91 female and 15 male) treated with (131)I for DTC met the inclusion criteria. The mean age of the patients was 45 years, age range 16-81 years. A total of 101 patients had complete 24 months follow-up following (131)I remnant ablation treatment. The mean (131)I dose administered after the first 6 months of follow- up was 3GBq while mean total dose was 4.9GBq, range 1.1-7.4GBq. Our results showed that at the end of the first 6 months post treatment, 58/101 patients had a negative (131)I-WBS. By the end of the 4th (131)I treatment at 24th months, the remaining 43 patients became negative for (131)I-WBS. We found increased Tg and negative (131)I-WBS in 2 of the 101 patients at the 24th months examination the so called Tg elevated negative (131)I-WBS (TENIS syndrome). The possible explanation of this syndrome is discussed. In conclusion, our study in DTC operated patients does not support the use of repeated diagnostic (131)I-WBS after an undetectable Tg because we found no Tg rebound in patients with negative (131)I-WBS, after 24 months of follow-up with serial measurements of Tg on and of suppression with L thyroxine.