Charles Michael Intenzo MD, Abstract Co-Author: Nothing to Disclose

Sung M. Kim MD, Presenter: Nothing to Disclose

David Capuzzi MD, Abstract Co-Author: Nothing to Disclose

Jeffrey Miller MD, Abstract Co-Author: Nothing to Disclose

Hung Dam MD, Abstract Co-Author: Nothing to Disclose

To determine if stunning occurs with a diagnostic dose of 5mCi of I-131 in patients with well-differentiated thyroid cancer (WDTC), and if stunning does occur, does it impact I-131 therapeutic efficacy and patient outcome?

A retrospective review involved 166 post-thyroidectomy patients for WDTC. Diagnostic whole-body scans were performed 48 hours after 5 mCi of I-131. The therapeutic doses of I-131 ranged from 100 to 250 mCi, gien on 5 to 7 days after the diagnostic scan. A post-therapy scan was then obtained 7 days later. Stunning was defined when the diagnostic scan showed activity that was subsequently decreased on the post-therapy scan. The patients were divided into 2 groups: Group NS did not show stunning and Group S revealed stunning. Patient outcome was considered successful if no functioning thyroid tissue and/or metastases were seen on subsequent one-year follow-up diagnostic I-131 scans. The treatment success rate for each group was defined as the total number of patients in the group divided by the number of patients with successful outcomes.

Group NS consisted of 135 patients, of whom 36 were lost to follow-up. Group S included 31 patients of whom 8 were lost to follow-up. Of the 99 patients studied in Group NS, 87 demonstrated a successful outcome at 12-month follow-up, resulting in a treatment success ratio of 87.9%. Of the 23 patients studied in Group S, 20 demonstrated a successful outcome 12 months later, yielding a treatment success rate of 87.0%. Overall, there was no statistically significant difference (p=0.56) in treatment success rates between Group NS (87.9%) and Group S (87.0%). Treatment success rates for metastases (mostly lymph nodes) were 88.06% (39/44) for Group NS and 83.3% (10/12) for Group S (p=0.55).

Thyroid stunning can occur with 5mCi of I-131 for diagnostic imaging. However, stunning has no signigicant effect on I-131 treatment efficacy, and therefore does not significantly impact patient outcome.

Intenzo, C, Kim, S, Capuzzi, D, Miller, J, Dam, H, Does Thyroid Stunning Affect Patient Outcome?.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4410227.html