Outcomes of Local-Regionally Advanced Thyroid Cancer after Surgery and 131-I Therapy Guided By Pre-Ablation 131-I Scans with SPECT/CT

Presentation Number: OR22-5
Date of Presentation: April 2nd, 2016

Natalja Rosculet*1, David T Hughes2, Nazanene H Esfandiari3 and Anca Mihaela Avram4
1University of Michigan Medial School, Ann Arbor, MI, 2University of Michigan, Ann Arbor, MI, 3Univ of Michigan, Ann Arbor, MI, 4Univ of Michigan Med Ctr, Ann Arbor, MI

Abstract

Background: Postoperative diagnostic 131-I scans with SPECT/CT complete staging and risk stratification of differentiated thyroid cancer (DTC), and guide 131-I therapy prescription for ablation of remnant tissue, or treatment of regional and distant metastatic disease. The objective of this study is to determine the outcome of local-regionally advanced DTC after surgery and 131-I therapy guided on pre-ablation scan findings.

Methods: 392 patients with regionally advanced DTC treated at the University of Michigan from 2007-2015 were retrospectively analyzed. Post-operatively all patients underwent pre-ablation 131-I scans with SPECT/CT and the presence of thyroid remnant tissue in the central neck, residual lymph node metastases and distant metastases were noted. Therapeutic 131-I prescription was based on information from surgical pathology, stimulated thyroglobulin (Tg) levels and scintigraphy findings.

Results: Pre-ablation SPECT/CT imaging detected unsuspected local-regional metastases in 49 patients (13%) and distant metastases in 33 patients (8%). The information from pre-ablation 131-I scans lead to changes in 131-I therapy prescription in 55 patients (14%) as follows: 45 more patients (11%) received medium RAI doses (75-150mCi), and 10 more patients (3%) received high RAI doses (>150mCi). At 1 year post-treatment, 51 patients were lost to follow-up, and therapeutic outcome was assessed in the remainder 341 patients: 279 patients (81%) with complete response (no evidence of disease and Tg <0.5ng/dl); 12 patients (4%) had biochemical incomplete response (persistent Tg with negative imaging); 50 patients (15%) had structural incomplete response (positive imaging). Of the 50 patients with structural incomplete response, all were detected by anatomic imaging studies (neck US, CT and PET/CT). 45 patients had negative follow-up 131-I scans, while in 5 patients follow-up 131-I scans were not performed.

Conclusions: Detection of residual regional and distant metastases on pre-ablation scans led to administration of adjusted 131-I therapeutic activities, as compared to "standard" ablation doses. This approach applied after total thyroidectomy with adequate compartmental neck dissection resulted in complete response to treatment in 81% of patients with advanced local-regional DTC. Most patients with structural incomplete response had negative follow-up 131-I scans and were detected on subsequent anatomic imaging, consistent with the existence of a reservoir of non-iodine avid disease at presentation. After appropriate 131-I treatment guided by pre-ablation scans, most cases with recurrent metastases occur in patients with altered tumor biology (non-iodine avid disease).

 

Nothing to Disclose: NR, DTH, NHE, AMA