Diagnostic 131I whole-body scintigraphy 1 year after thyroablative therapy in patients with differentiated thyroid cancer: correlation of results to the individual risk profile and long-term follow-up.

PURPOSE: (131)I whole-body scan (WBS) and serum thyroglobulin (TG) are important in detecting thyroid remnants or recurrent disease in patients with differentiated thyroid cancer. Usually, a diagnostic WBS is carried out 6 months after ablation to exclude residual disease. We retrospectively analysed results of a second routine diagnostic WBS and TG measurements at 1 year after thyroablation and correlated these to the risk profile of patients with long-term follow-up. METHODS: A total of 197 patients were followed up after thyroidectomy and ablative (131)I therapy. Follow-up included clinical examination, radioiodine WBS and thyroid-stimulating hormone (TSH), free thyroxine and TG measurements at 3-6 months and 1 year after ablation. WBS (+) patients received a therapeutic activity of (131)I. The risk profile of patients was defined according to clinical results before the 1-year control. Clinical results at 1 year after ablation were analysed in correlation to the patient risk profile and long-term follow-up data (mean 7.2 years). RESULTS: One year after thyroablation, 95.8% of low-risk patients had no residual disease when diagnostic WBS was carried out using 370 MBq (131)I; 4.2% of low-risk patients had residual disease at this time point. In the high-risk group of this cohort, 54.5% were disease-free 1 year after ablation, but 45.5% demonstrated residual disease. After the 1-year control, 94% of all applied radioiodine therapies were executed in the high-risk group, compared with 6% in the low-risk group (p < 0.01). CONCLUSION: A second routine WBS 1 year after thyroablation is not indicated in low-risk patients. Risk stratification according to the early clinical course effectively identified patients with higher likelihood of persistent or recurrent disease in the long-term follow-up.

Regional lymph node involvement in T1 papillary thyroid carcinoma: a bicentric prospective SPECT/CT study.

PURPOSE: Hybrid imaging combining single photon emission computed tomography (SPECT) with (131)I and X-ray computed tomography (CT) performed at radioablation (RA) for thyroid carcinoma more accurately detects regional lymph node metastases (LNM) than does planar imaging. In this bicentric prospective study we used hybrid imaging in conjunction with histopathological examination to measure LNM frequency in a consecutive group of patients referred for RA due to stage T1 papillary thyroid carcinoma (PTC). METHODS: At the Departments of Nuclear Medicine of the Ludwig Maximilian University of Munich and the Friedrich Alexander University of Erlangen-Nuremberg SPECT/spiral CT is routinely performed in all PTC subjects at the time of RA. Screening of our SPECT/CT databases for PTC patients with T1 histology produced 98 patients from Munich and 53 patients from Erlangen, including 96 of 151 patients with microcarcinoma. In 69 patients of the entire group, cervical lymph node dissection had been performed, whereas nodal staging in the remaining 82 subjects was based on SPECT/CT. RESULTS: LNM incidence in the whole group was 26% [95% confidence interval (CI): 20-33%] versus 22% (95% CI: 15-31%) in the microcarcinoma subgroup. SPECT/CT was more accurate in 24.5% of our patients than planar imaging with regard to nodal staging. CONCLUSION: LNM occurs in one quarter of all patients with T1 PTC, and also in the subset with microcarcinoma. Performing (131)I SPECT/CT, either with therapeutic or diagnostic radioactivities, directly after thyroidectomy should provide more accurate staging of T1 PTC, thus facilitating optimal therapeutic management.