Evaluation in a mouse model of a thyroid-blocking protocol for 131I antibody therapy (short communication).
OBJECTIVE
We describe a murine model to evaluate variations of a published multicenter thyroid blocking protocol described for 131I antibody therapy, using doses of blocking agents proportional to those used in man. Variables include duration of super-saturated potassium iodide (SSKI) pretreatment and use of supplemental KClO4.


METHODS
Whole-body activity measurements were performed 0, 24, 48 and 72 hours following 131I-NaI administration in control and thyroid-blocked mice. Retained whole-body activity was calculated as a percentage of the injected dose (%ID), primarily reflecting radioiodine sequestered in the thyroid gland. In blocked groups, SSKI was begun one or 7 days preceding 131I-NaI therapy, and was supplemented in one half of the cases with KClO4 from time of therapy.


RESULTS
In control mice, %ID was 11.23 +/- 1.47%, 10.15 +/- 1.11% and 9.29 +/- 1.50% at 24, 48 and 72 hrs respectively. %IDs of blocked groups were markedly lower than controls (p = .0001). In the one day SSKI pretreatment group, %ID was reduced from 1.73 +/- 0.58, 1.42 +/- 0.45 and 1.20 +/- 0.38 at 24, 48 and 72 hours to 0.49 +/- 0.08, 0.50 +/- 0.07 and 0.44 +/- 0.06 with addition of supplemental KClO4. In the 7 day SSKI pretreatment group, %ID was reduced from 1.87 +/- 0.73, 1.48 +/- 0.49 and 1.36 +/- 0.57 at 24, 48 and 72 hours to 0.60 +/- 0.36, 0.45 +/- 0.13 and 0.41 +/- 0.14 with addition of supplemental KClO4. %IDs in the 7 day pretreatment animals were not statistically different from those in the one day pretreatment groups (all p >> 0.05).


CONCLUSIONS
SSKI reduces retention of radioiodide approximately six-fold whereas supplemental KClO4 enhances thyroid blocking an additional three-fold. Seven day SSKI pretreatment appears no more effective than one day pretreatment.
Zuckier
L S
LS
Department of Nuclear Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Li
Y
Y
Chang
C J
CJ
D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use; D051379:Mice; D015337:Multicenter Studies as Topic; D011193:Potassium Iodide / Q000493:pharmacokinetics / Q000627:therapeutic use; D016499:Radioimmunotherapy; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics* / Q000627:therapeutic use; D013961:Thyroid Gland
D000911:Antibodies, Monoclonal; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D011193:Potassium Iodide