Sung M. Kim MD, Presenter: Nothing to Disclose

Gunsel Acikgoz MD, Abstract Co-Author: Nothing to Disclose

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

Serge Jabbour MD, Abstract Co-Author: Nothing to Disclose

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

Serum Tg level and % iodine uptake seen in the diagnostic whole body scan can predict an amount of functining residual thyroid tissue or metastatic tumor. However, these two vaiables can be dissociated each other. To investigate the relationship between serum Tg level and % iodine uptake and identify agreement and disagreement between two. To find out, if disagreement occurs, whether this is related to the presence of non-iodine concentrating tumor.

A total of 30 patients who had a diagnostic iodine scan after post thyroidectomy were analyzed for % iodine uptake of thyroid remnant or metastatic lesions. The % iodine uptake values were correlated with post-thyroidectomy serum Tg level, TSH and Mayo Clinic MAICS scores. The patient age ranges from 21 to 81 yr-old with a mean age of 51.4. There were 24 women and 6 men. There were 12 in stage 1, 10 in stage 2, 7 in stage 3 and 1 in stage 4.

Percent iodine uptake ranged from 0.7 % to 17.8% with a median % uptake value of 2.4% (95% confidence interval: 1.6 to 3.8% ). Background % uptake was 0.4%. Tg levels ranged from 0.3 to 9230 with a median value of 12.6 ng (95% CI: 4.7-28.6). Tg-antibody was noted in 4 patients. There was strong association between Tg and % uptake (p<0.03) and a weak correlation between Tg and MAICS scores (p<0.08) and no correlation with TSH (p<0.6). Regression analysis showed a correlation of log(%uptake) and log(Tg)as follows: Log(Tg)=0.7534 + 1.0268 Log(%uptake). Discordant finding between Tg and % iodine uptake was noted in 7 patients in whom % iodine uptake underestimates a burden of remnant thyroid or metastatic tumor, namely iodine-not concentrating tumor/tissue. A patient with Tg of 9230 showed only thyroid bed uptake but no metastatic lesions in the lungs on a diagnostic scan.

Percent iodine uptake value widely varies upto 20-fold among individuals. Serum Tg or % iodine uptake can be estimated using the relationship between two. When discordant relationship occurs, it indicates the presence of iodine-not-concentrating tumor. A diagnotic iodine scan underestimates predicting a burden of functioning residual thyroid or cancer in 7/30 patients.

Kim, S, Acikgoz, G, Intenzo, C, Jabbour, S, Miller, J, Predicting Iodine-not-concentrating Thyroid Cancer: Understanding Relationship between Serum Thyroglobulin Level and Per Cent Iodine Uptake.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4410053.html