Radioiodine scans have limited value in
thyroid-cancer patients with undetectable serum thyroglobulin values
(July 2002)
The background of
the study. Most patients with thyroid cancer are treated
with thyroidectomy and then, given primarily to destroy any remaining
normal thyroid tissue. In the past, most patients later had a scan,
several weeks after withdrawal of thyroxine (T4) therapy, to verify
destruction of the thyroid remnant and to detect persistent cancer.
This retrospective study was done to determine if scanning at this
time provided useful information.
How the study was done. The study
subjects were 315 patients (mean age, 41 years) with papillary or
follicular cancer of the thyroid who had undetectable (<3 ng/ml)
serum thyroglobulin concentrations after cessation of T4 therapy
between 6 and 12 months after initial treatment. All initially underwent
near-total thyroidectomy and therapy. Six to 12 months later, T4
was discontinued. Serum thyroglobulin was measured and a diagnostic
whole-body scan was done. Thereafter, the patients were examined
yearly and had periodic measurements of serum thyroglobulin and
periodic diagnostic whole-body scans after the withdrawal of T4
therapy.
The results of the study. The diagnostic
whole-body scan done 6 to 12 months after initial treatment in the
315 patients revealed no uptake in 71 percent and uptake in the
bed of the thyroid in 29 percent. During subsequent follow-up, which
ranged from 9 to 19 years (mean, 12), 89 percent of the patients
had persistently undetectable serum thyroglobulin concentrations
and negative diagnostic whole-body scans, 9 percent had persistently
undetectable serum thyroglobulin concentrations but uptake in the
thyroid bed, and 1 percent had recurrent thyroid carcinoma.
The conclusions of the study. Patients
with thyroid carcinoma who have undetectable serum thyroglobulin
concentrations rarely have abnormal I-131 scans, and very few have
recurrent carcinoma.
The original article. Pacini F,
Capezzone M, Elisei R, Ceccarelli C, Taddei D, Pinchera A. Diagnostic
131-iodine whole-body scan may be avoided in thyroid cancer patients
who have undetectable stimulated serum Tg levels after initial treatment..
J Clin Endocrinol Metab 2002;87:1499-501.
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