The efficacy of iodine-131 therapy in patients
with thyroid carcinoma is increased by a low iodine diet
(July 2003)
The background of
the study. Patients with thyroid carcinoma are often treated
with radioactive iodine (I-131) after surgery to destroy any remaining
normal thyroid tissue and thyroid carcinoma. The effect of I-131
to destroy thyroid remnants may be increased by dietary iodine restriction.
In this study the ability of I-131 to destroy thyroid remnants was
compared in patients who ate a low-iodine diet or their usual diet
before treatment.
How the study was done. The study
subjects were 120 patients with papillary or follicular carcinoma
who underwent thyroidectomy between 1986 and 1998. Four weeks after
surgery 24-hour I-131 uptake was measured. The patients were then
treated with a high dose of I-131 (mean, 76 mCi). Those patients
treated from 1986 to 1991 ate their usual diet, whereas those treated
from 1992 to 1998 ate a diet that reduced their lower urinary iodine
excretion to ≤49 µg/day for four days before I-131 therapy.
The patients were then treated with thyroxine for six months, at
which time it was stopped, and thyroid uptake of I-131 scan was
again measured.
The results of the study. There
were 59 patients in the low-iodine diet group and 61 patients in
the usual diet group. The characteristics of the patients, including
tumor type, in each group were similar. The thyroid uptake of I-131
was higher in the low-iodine diet group before I-131 therapy, and
they had more severe hypothyroidism and were more likely to have
no detectable thyroid I-131 uptake and a low serum thyroglobulin
concentration at the time of the second study.
The conclusions of the study. The
efficacy of I-131 in destroying thyroid remnants in patients with
thyroid carcinoma is increased if the patients eat a low iodine
diet before I-131 administration.
The original article. Pluijmen MJ,
Eustatia-Rutten C, Goslings BM, Stokkel MP, Arias AM, Diamant M,
Romijn JA, Smit JW. Effects of low-iodide diet on postsurgical radioiodide
ablation therapy in patients with differentiated thyroid carcinoma.
Clin Endocrinol 2003;58:428-35.
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