A case of stunning of lung and bone metastases of papillary thyroid cancer after a therapeutic dose (3.7 GBq) of 131I and review of the literature: implications for sequential treatments.

Thyroid stunning is usually defined as the inhibition or suppression of iodide trapping by remnant thyroid tissue or by functioning metastases following a diagnostic dose of 131I. The risk of stunning increases progressively with larger doses. Because the threshold above which this effect occurs in thyroid remnants seems to be between 37 MBq and 111 MBq of 131I, therapeutic 131I doses of 3.7 GBq may cause stunning. We describe stunning of papillary thyroid cancer lung and bone metastases after a therapeutic dose of 131I (3.7 GBq). A T1 bone metastasis and bilateral lung metastases were diagnosed by post-therapeutic dose whole-body scan. Nuclear MRI detected another lesion at T4, whose 131I fixation was not obvious. An additional 0.7 GBq were given after recombinant TSH, 37 days after the therapeutic dose; 24 h later, uptake by the lung and T1 metastases had disappeared, but trapping was again seen 6 months later on the post-therapeutic scan. This re-appearance is evidence in favour of the transitory and reversible character of stunning, and confirms its correspondence to the decreased ability of viable thyroid cells to trap iodine and not to their destruction. A better understanding of stunning would make it possible, in the event of rapidly progressing disease and in conjunction with recombinant thyroid stimulating hormone (TSH), to give several therapeutic doses of 131I in close succession without each dose hampering the effectiveness of the subsequent one.

Upper retropharyngeal node involvement in differentiated thyroid carcinoma demonstrated by 131I scintigraphy.

We report four patients with papillary thyroid cancer who had upper retropharyngeal node involvement demonstrated by 131I scintigraphy. Three patients presented with a thyroid nodule and enlarged jugular nodes. Total thyroidectomy was performed with node dissection. Pathology demonstrated papillary carcinoma with several metastatic nodes. 131I scanning 4 weeks after surgery demonstrated increased uptake in an upper retropharyngeal node. In one patient, thyroidectomy had been performed 21 years previously. Increased thyroglobulin level led to 131I scanning, which showed focal retropharyngeal uptake. All four patients had asymmetrical uptake at mouth level with focal uptake close to the sagittal plane. A lateral projection showed focal uptake between the base of the skull and the mandibular angle, behind the region of the mouth and nose. CT in all cases and MRI in one case confirmed the presence of an enlarged node. The mass was removed surgically in two patients and pathology confirmed the papillary nature of the metastatic node. Two patients were treated by 131I. Focal uptake of 131I in the region of the mouth is ambiguous, since salivary uptake of 131I is a common finding on scintigraphy. In cases of asymmetrical uptake in the region of the mouth, a lateral projection of the head therefore allows the correct diagnosis.

Decreased uptake of therapeutic doses of iodine-131 after 185-MBq iodine-131 diagnostic imaging for thyroid remnants in differentiated thyroid carcinoma.

We performed a prospective random study to assess possible thyroid stunning by a 185-MBq iodine-131 dose used to diagnose thyroid remnants. Patients with differentiated thyroid carcinoma were included after total or near-total thyroidectomy. They were randomly assigned to two groups. In group 0 (G0, 32 patients), iodine-123 administration only was used to diagnose thyroid remnants and/or metastasis, so that no thyroid stunning by 131I would occur. In group 1 (G1, 19 patients), diagnostic imaging was performed with 123I and 185 MBq 131I. 123I imaging was less sensitive than 131I imaging in identifying thyroid remnants in both groups (94%). Thyroid uptake of 123I was measured in both groups (at 2 h) and was not significantly different between the groups. Patients with thyroid remnants who remained in the study (28/32 in G0, 17/19 in G1) were treated with 370 MBq 131I, 5 weeks after treatment (mean time, range 12-84 days). In 12/17 G1 patients thyroid uptake measurement was repeated immediately before treatment. Uptake was equal to 1.97% +/- 0.71% and significantly lower (P < 0.05) than the previous measurement (3.76% +/- 1.50%). Patients were imaged 7 days after administration of the therapeutic dose and the images were compared with the diagnostic images. In 28/28 G0 patients thyroid remnants were unchanged and clearly seen. In 5/17 G1 patients, however the remnants were hardly identified, although they had been clearly seen at the time of diagnosis. We conclude the following: (1) a diagnostic dose of 185 MBq 131I decreases thyroid uptake for several weeks after administration and can impair immediate subsequent 131I therapy; (2) 123I is slightly less sensitive than 131I in identifying thyroid remnants; and (3) the need to scan for thyroid remnants remains to be confirmed, since only 2/51 patients enrolled in this study were not treated with 131I.

Radioiodine therapy of the autonomous thyroid nodule in patients with or without visible extranodular activity.

UNLABELLED: Patients with an autonomously functioning thyroid nodule (ATN) may be present with various clinical, biochemical and scintigraphic features. To optimize 131I dose planning and treatment timing in these patients, relationships between dosimetric data and clinical follow-up events must be established. METHODS: We retrospectively reviewed the records of 88 patients who received 131I (intended dose of 80 Gy) for an ATN, of whom 39 had evidence of extranodular activity (ENA) and 76 presented with overt thyrotoxicosis. In all of the patients, dosage calculation was monitored to estimate precisely both beta and gamma absorbed doses received by the ATN and the nodule-free lobe. The mean duration of follow-up was 75 mo (max 180) and always included biochemical thyroid tests. Finally, we compared the dosimetric profiles of four dosage schemes which had been normalized by simulation to ensure that the same absorbed dose threshold value was always delivered to the ATN. RESULTS: About 75% of the patients were cured at 6 mo for a mean 305 MBq administered. The absorbed doses delivered to the nodule-free lobe ranged from 12% (no ENA) to 86% (ENA) of the values delivered to the ATN, mainly in the form of beta irradiation. Life-table estimates for hypothyroidism and death were 9.6% and 22% at 75 mo, respectively. Hypothyroidism mainly developed in patients with nonsuppressed TSH levels but regardless of ENA, which often accounted for multifocal disease. CONCLUSION: We suggest that fixed doses bordering on 370 MBq are advizable in younger individuals and in patients with mild thyrotoxocosis, while 555 MBq-740 MBq can be administered in other patients and that ENA indicates multifocal autonomy in patients with toxic ATN and is a further indication for radioiodine treatment which should be begun as soon as possible to avoid the development of cardiac complications.

Influence of dose selection on absorbed dose profiles in radioiodine treatment of diffuse toxic goiters in patients receiving or not receiving carbimazole.

We retrospectively reviewed the records of 224 patients with diffuse goiters treated with radioiodine, half of which received carbimazole. In all the cases, we carefully monitored the calculation of dosage. A lower percentage of early hypothyroidism but a higher failure rate was observed in the carbimazole subgroup. Nevertheless, after one year, a constant (4.5%) incremental rate of hypothyroidism was found regardless of carbimazole administration. Since we were able to precisely estimate the absorbed doses in our series, we evaluated by simulation the dosimetric profiles of nine methods of dose selection (MDS). These MDS were calibrated in such a way that the same threshold value of absorbed dose would always be reached at the thyroid level. We showed that the more elaborate the MDS, the more accurate the irradiation at the thyroid level and the lower the radiation dose administered. In patients not receiving carbimazole, a rapid MDS using modified early uptake measurements to predict the 24-hr actual value was found to be advisable. With patients receiving carbimazole and if a goal is to delay the occurrence of hypothyroidism, we advise MDS based on either a 48-hr uptake or on the calculation of the individual half-life.

Temporary ovarian failure in thyroid cancer patients after thyroid remnant ablation with radioactive iodine.

We studied ovarian function retrospectively in 66 women who had regular menstrual cycles before undergoing complete thyroidectomy for differentiated thyroid cancer and subsequent thyroid remnant ablation with 131I. Eighteen women developed temporary amenorrhea accompanied by increased serum gonadotropin concentrations during the first year after 131I therapy. No correlation was found between the radioactive iodine dose absorbed, thyroid uptake before treatment, oral contraceptive use, or thyroid autoimmunity. Only age was a determining factor, with the older women being the most affected. We conclude that radioiodine ablation therapy is followed by transient ovarian failure, especially in older women.

[Solid cold thyroid nodule. Current data]. / Le nodule froid plein thyroïdien. Données récentes.

Attitudes adopted when confronted with a solid cold thyroid nodule are analyzed in the light of recent developments in paraclinical data represented essentially by results of immunological, ultrasound and fine needle cytopuncture examinations. The use of these new surveillance technics frequently allows surgery to be deferred, while if on the contrary operation is decided then it usually now involves both thyroid lobes to avoid nodular recurrence and repeat surgery. Postoperative follow up surveillance is essential to ensure individual adaptation of attitude: therapeutic abstention, suppressive or possibly compensatory treatment.

[Serum thyroglobulin is elevated in patients with heterogeneous goiter during radioiodide scintigraphy, but normal in those with homogeneous goiter]. / La thyroglobuline sérique est élevée chez les patients présentant un goitre hétérogène lors de la scintigraphie au radio-iode mais normale chez ceux dont la carte est homogène.

Serum thyroglobulin (Tg) levels were determined in 98 biologically euthyroid patients with a diffuse or nodular goiter, and compared to values observed in 33 control subjects. Based on the results of clinical examination and thyroid scanning with radioiodine, patients were divided into 3 groups: group 1 with homogeneous diffuse goiters, group 2 with heterogeneous diffuse goiters without palpable nodules, and group 3 with solitary hypofunctioning nodules. The control group had a mean Tg of 37 +/- 15 micrograms/l. Group 1 (n = 32) had a mean Tg of 46 +/- 28 micrograms/l; six (19%) had an elevated Tg level (level greater than 74 micrograms/l). Group 2 (n = 30) had a mean Tg of 133 +/- 134 micrograms/l; fourteen (47%) had an elevated Tg level. Group 3 (n = 36) had a mean Tg of 188 +/- 191 micrograms/l; twenty (56%) had an elevated Tg level. The comparison of Tg between patient groups, and between patients groups and the control group, showed a significantly higher value in the groups of hypofunctioning nodules and heterogeneous diffuse goiters. It is concluded that the elevated serum Tg level in patients with a diffuse or nodular simple goiter is commonly associated with heterogeneity of the thyroid scan.

Serum thyroglobulin levels in hypofunctioning nodules before and after surgery.

Serum thyroglobulin (Tg) level was determined in 34 biologically euthyroid patients having benign hypofunctioning nodule, before and after surgery. Based on the results of thyroid scanning with radioiodine, 2 groups of patients were considered. Group 1 (n = 18) had solitary hypofunctioning nodule with an otherwise normal thyroid gland and group 2 (n = 16) had hypofunctioning nodule inside an enlarged and/or heterogeneous thyroid. Results were compared to a group of 30 control subjects. Mean Tg level was significantly elevated in both groups 1 and 2 before surgery. No significant difference was found between group 1 and group 2. After surgical removal of the hypofunctioning nodule (follicular adenoma), mean Tg level was normalized in group 1 and decreased but still remained elevated in group 2. It is concluded that the observed elevated serum Tg level is due to the presence of hypofunctioning nodule and/or heterogeneous thyroid tissue. Thus, Tg determination may be useful in the follow-up of operated hypofunctioning nodules in order to detect abnormality in the remaining thyroid tissue.