[Effect of iodine application during radioiodine therapy in patients with impending therapy failure].
OBJECTIVE
We investigated whether additional application of "cold" iodine after therapy with radioiodine could result in a prolongation of the effective half life of iodine-131 and would thus lead to an increase of the effective thyroid radiation dose.


METHODS
Time-activity-curves after therapy with radioiodine were analysed in 25 patients (16 women, 9 men). Nine patients suffered from autonomously functioning thyroid nodules, 5 from autonomous multinodular goiter and 11 from Graves' disease. These patients had an effective half life shorter than 4 days resulting in an undertreatment of > 20% with respect to the desired effective thyroid radiation dose. 2-4 days after therapy with radioiodine all patients received "cold" iodine for three days in a dose of 3 x 200 micrograms per day.


RESULTS
In 14 of the 25 patients an increase of the effective half life was observed. Patients with an autonomously functioning thyroid nodule showed a mean increase of the effective thyroid radiation dose of 40 +/- 44 Gy, patients with toxic multinodular goiter of 29 +/- 30 Gy and patients with Graves' disease of 37 +/- 37 Gy.


CONCLUSIONS
Additional application of "cold" iodine after therapy with radioiodine can prolong the effective half life in selected patients. We suspect a correlation with the thyroid iodine pool. This will be the basis for further investigations hopefully resulting in a better patient preselection to determine who might respond to this therapy.
Urbannek
V
V
Klinik und Poliklinik für Nuklearmedizin, Medizinische Einrichtungen, Universität zu Köln, Deutschland.
Schmidt
M
M
Moka
D
D
Hillger
H W
HW
Voth
E
E
Wellner
U
U
Schicha
H
H
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006044:Goiter, Nodular / Q000532:radiotherapy*; D006111:Graves Disease / Q000532:radiotherapy*; D006207:Half-Life; D006801:Humans; D007455:Iodine / Q000493:pharmacokinetics / Q000627:therapeutic use*; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D016606:Thyroid Nodule / Q000532:radiotherapy*; D017211:Treatment Failure; D016896:Treatment Outcome
D007457:Iodine Radioisotopes; D007455:Iodine