Joseph Rine Payne MD, Presenter: Nothing to Disclose

Elizabeth Cheatham, Abstract Co-Author: Nothing to Disclose

M. Elizabeth Oates MD, Abstract Co-Author: Nothing to Disclose

Thyroidal tissue stunning remains controversial. Is it a real phenomenon? Does it affect ablation success? Our aim was to develop a simple quantitative approach to measure potential stunning and determine if it can predict ablation success.

We retrospectively evaluated 44 patients who had undergone recent thyroidectomy for differentiated thyroid cancer. All had a pre-ablation 185 MBq 131I NaI whole-body scan, radioiodine ablation therapy (3700-7400 MBq) with a post-ablation whole-body scan, and 6-12 month follow-up diagnostic 185 MBq whole-body scan. The study population included patients with single focus/remnant (n=12) and those with multiple locoregional foci (n=32). Regions-of-interest were drawn by an experienced technologist to measure and compare counts per pixel normalized to background in each focus on the pre-ablation and post-ablation scans.

Of 44 patients, 31 (70%) exhibited quantitative stunning in at least one I-avid focus as defined by any decrease in the normalized counts on the post-ablation scan compared to the pre-ablation scan. Incomplete ablation, defined as the presence of I-avid disease on follow-up scan and/or serum thyroglobulin > 0.3 ng/mL, occurred in 17/44 (39%) patients. Of those 17, stunning was evident in 14 (82%) and not in 3 (18%). In the subgroup of 12 with a single I-avid focus, 4 (33%) experienced incomplete ablation; all 4 showed stunning. In the subgroup of 32 with multiple I-avid foci, 13 (41%) patients were incompletely ablated; 10/13 (77%) showed stunning.

Using pre-ablation and post-ablation scans, a simple quantitative approach can be employed to measure potential stunning after initial 131I NaI therapy. Some degree of stunning is evident in the majority of patients. Furthermore, the presence of stunning is not overrated because it appears to predict an adverse effect on ablation success.

Thyroidal tissue stunning, while controversial, can be quantitatively assessed and appears to predict an adverse effect on ablation success in patients with remnant(s) or locoregional metastasis(es).

Payne, J, Cheatham, E, Oates, M, Is Stunning Overrated? A Simple Quantitative Approach to Predicting Stunning in Patients with Differentiated Thyroid Carcinoma.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12031323.html