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J Nucl Med. 2008; 49 (Supplement 1):323P
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Oncology-Basic Science: Therapy, Metrics & Intervention

Therapy, Metrics & Intervention Posters

Comparison of the blood biokinetics of I-124 and I-131 in patients with well-differentiated thyroid cancer (WDTC)

F. Atkins1, D. Van Nostrand1, S. Moreau1, C. Butler1, J. O'Neil1, K. Burman2 and L. Wartofsky2

1 Nuc Med; 2 Endo, Wash Hosp Ctr, Washington, District of Columbia

1368

Objectives: Validate the equivalent blood biokinetics of two orally administered radioiodines, I-131 and I-124.

Methods: Patients (pts) who (1) had WDTC, (2) were suspected of having metastases, and (3) were referred for I-131 dosimetry could be enrolled in a protocol that involved separate administrations of I-131 (2 mCi) and I-124 (1.7 mCi). Pt preparation was either by thyroid hormone withdrawal (THW) or rhTSH. Pts who were THW (n=3) received the I-131 first and 4 days later, I-124 was administered. Pts stimulated with rhTSH (n=7) were randomized as to the order of the tracer doses. Heparinized blood samples were collected for both radioiodines at approximately 2, 24, 48, 72, and 96hr post dosing. Whole blood samples (1 ml) were counted at the end of each phase in a NaI(Tl) well-counter along with calibration samples. The activity concentrations were first corrected with the appropriate decay constant, and then both clearance curves decayed for I-131. Differences between the two measurements were statistically evaluated using paired two-tailed T-test. An effective half-life was determined for each patient in the group based on a single exponential regression (ProStat v4.5) to both sets of clearance data.

Results: Ten patients have been enrolled and analyzed. The average effective half-life in the blood compartment was 14.7 +/- 5.3 hrs for I-124 and 14.5 +/- 5.7 hrs for I-131 with the largest relative difference for any patient being 8.2% (average intra-patient deviation of 1.2%).

Conclusions: There is no statistically significant difference (P=0.38) between the clearance of I-124 and I-131 in blood following oral administration of either radioiodine in patients with WDTC.

Research Support: Genzyme and Latham Fund





This Article
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Right arrow Email this article to a friend
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Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Google Scholar
Right arrow Articles by Atkins, F.
Right arrow Articles by Wartofsky, L.
PubMed
Right arrow Articles by Atkins, F.
Right arrow Articles by Wartofsky, L.