The comparative value of serum thyroglobulin measurements and iodine 131 total body scans in the follow-up study of patients with treated differentiated thyroid cancer

The detection of a unique antigen associated with papillary thyroid carcinoma

We produced antibodies against a thyroid papillary carcinoma homogenate (PCAb) and analyzed antigens recognized by this antibody using western blotting. Fifty-four thyroid tissue specimens and 6 control tissue specimens obtained from non-thyroid carcinoma (gastric tissue, colon and liver) were analyzed. Consequently, an antigen of 40 kDa in size was found in 16 of 16 (100%) of papillary thyroid carcinoma from primary lesions and in 2 of 2 (100%) papillary thyroid carcinoma from metastatic foci, whereas it was not detected in thyroid tissue samples from follicular carcinoma, anaplastic carcinoma, follicular adenoma, adenomatous goiter, Graves' disease and normal thyroid tissues. The reactivity of thyroglobulin antiserum (TgAb) to this 40 kDa antigen was tested by western blotting and showed that TgAb did not appear to recognize the 40 kDa antigen. Moreover PCAb, after treatment with Tg, still reacted with this 40 kDa antigen. Therefore, this 40 kDa antigen might be different from Tg. Furthermore, to inspect the structure of this antigen, the effect of some chemicals and enzymes such as 2-mercaptoethanol, sodium dodecyl sulfate, ethanol and protease on the reactivity of PCAb to the 40 kDa antigen were analyzed. The results of these experiments suggested that this 40 kDa antigen may have a peptide structure. To our knowledge, the finding reported here represents the first demonstration of the protein specifically present in papillary thyroid carcinoma. Further investigations should elucidate the characteristics of this antigen and may contribute to definitive diagnosis of thyroid carcinoma as well as improving the understanding of the mechanisms involved in developing the thyroid carcinoma.

Value of stimulated serum thyroglobulin levels for detecting persistent or recurrent differentiated thyroid cancer in high- and low-risk patients

BACKGROUND

Serum thyroglobulin determination has been reported to be a sensitive indicator of persistent or recurrent differentiated thyroid cancer of follicular cell origin (DTC) after total thyroidectomy. The purpose of this investigation was to determine the accuracy of serum thyroglobulin levels in predicting persistent or recurrent DTC in euthyroid and hypothyroid patients.

METHODS

One hundred ninety consecutive patients with DTC of follicular cell origin who had 4 or more thyroglobulin levels measured after total thyroidectomy were retrospectively evaluated. One hundred fifteen patients had serum thyroglobulin levels measured when hypothyroid for radioiodine scanning or ablation. Serum thyroglobulin levels were determined by commercial assays. One hundred twenty-two patients less than 45 years old were considered at low risk, whereas 68 patients more than or equal to 45 years old were considered at high risk on the basis of TNM classification. The mean follow-up period was 62 months.

RESULTS

After thyroidectomy with or without central or modified radical neck dissection 120 patients had normal thyroglobulin levels (< or = 3 ng/mL) while receiving thyroid hormone. One hundred thirteen of the 120 patients (94%) with normal serum thyroglobulin levels had no evidence of recurrent tumor, whereas 6% (7 patients) had persistent or recurrent disease. Among 76 patients with persistent (28 patients) or recurrent (48 patients) disease, 70 had a serum thyroglobulin level > 3 ng/mL while receiving thyroid hormone. Overall, 14 of 115 patients, including 2 of 61 (3%) in the high-risk group and 12 of 54 (22%) in the low-risk group, only had elevated serum thyroglobulin levels when hypothyroid with high serum thyroid-stimulating hormone (TSH) levels documenting persistent or recurrent disease. In 1 patient the serum thyroglobulin level (240 ng/mL) was falsely elevated probably as a result of interfering antibodies because no tumor was identified surgically or pathologically, and the thyroglobulin concentration was < 3 ng/mL when analyzed in 3 other laboratories.

CONCLUSION

Serum thyroglobulin testing is sensitive (91%) and specific (99%) for identifying patients with persistent or recurrent differentiated thyroid cancer. Serum thyroglobulin levels are most precise when patients are hypothyroid (high TSH) and may be unreliable in patients with antithyroglobulin antibodies. We recommend TSH-stimulated thyroglobulin testing for all patients after total thyroidectomy for differentiated thyroid cancer of follicular cell origin regardless of patient age or risk group.

Undetectable serum thyroglobulin in a patient with metastatic follicular thyroid cancer

The case of a 54-year-old woman with metastatic follicular thyroid cancer and undetectable serum thyroglobulin is presented. Many years after the patient had a subtotal thyroidectomy for a large goiter that had no clear evidence of malignancy, metastatic bone disease developed. When the bone metastases were detected and during the follow-up period, serum thyroglobulin values remained undetectable, but radioiodine uptake in the metastases was abundant. This case indicates that the combination of 1-131 scintigraphy and serum thyroglobulin values is superior to the measurement of serum thyroglobulin alone in detecting well-differentiated, metastatic thyroid cancer.

Two-dimensional electrophoretic analysis of membranous protein from human thyroid tissues and cancer cell lines

Thyroid neoplasm is the most commonly encountered neoplastic disorder in endocrine clinics. Thyroid scan, ultrasonography, and fine needle aspiration cytology (FNAC) are used as diagnostic tools to differentiate a malignant nodule from a benign lesion. There are certain limitations and pitfalls in FNAC, especially in the diagnosing of follicular tumors. The lack of characteristic findings or a specific tumor marker are the most common problems in the preoperative diagnosis of thyroid follicular carcinoma. Although serum thyroglobulin level has been used as a tumor marker for post-operative, well-differentiated thyroid cancer, the assay cannot be used for preoperative diagnosis of thyroid carcinoma. In this study, various thyroid tissues and cancer cell lines including CGTH W-1, CGTH W-3, RO 82 W-1, SW 579 cell lines were used for the investigation of tumor markers. Specific spots were identified in the area near the 60 kDa molecular mass protein and isoelectric point (pI) 5.9 of the CGTH W-1 cell line. These spots could not be found in the papillary or anaplastic thyroid cancer cell lines. Another spot with a molecular weight of about 9.8 kDa with a low pI of 4.8 was present in the CGTH W-1 and RO 82 W-1 cell lines. This spot appeared to be a tumor marker of follicular cancer cells. This spot could not be found in the papillary and anaplastic cancer cell lines and other benign thyroid tissues. Specific proteins that were identified in this study may be useful as tumor markers for follicular thyroid carcinoma.

Positron emission tomography for detecting iodine-131 nonvisualized metastasis of well-differentiated thyroid carcinoma: two case reports

To investigate the usefulness of positron emission tomography (PET) in detecting I-131 nonvisualized metastatic foci of well-differentiated thyroid carcinoma (WDTC), 2 patients with papillary and follicular thyroid carcinoma respectively, were studied with I-131 total body scan, thallium-201 scan, Tc99m bone scan and [18F]-2-deoxy-2-fluoro-D-glucose (FDG) PET. Case 1 showed no metastatic lesion in I-131 (up to 150 mCi) total body scan, 1 anterior mass in thallium-201 scan, none in Tc99m bone scan and 7 including the main anterior mediastinal mass in FDG-PET. Case 2 showed 2 metastatic lesions in I-131 (150 mCi) total body scan, 11 bony metastatic lesions in Tc99m bone scan and 13 in FDG-PET. However, lower extremities were not scanned in FDG-PET. Tumor/background ratio of 1.5 or above is needed to be visualized grossly. The FDG-PET tumor/background ratios are higher than those of thallium-201 except in one site. In conclusion, I-131 scintigraphy is still the first line method to use in detecting WDTC recurrence and metastasis, as I-131 has the advantage of being both a therapeutic and imaging agent. For I-131 nonvisualized metastasis of WDTC, thallium scintigraphy and FDG-PET may be considered. Even though FDG-PET has better sensitivity, resolution imaging and spatial localization, this has to be balanced with its higher cost when compared with thallium scintigraphy.

High-resolution ultrasound associated with aspiration biopsy in the follow-up of patients with differentiated thyroid cancer

OBJECTIVE: To assess the value of ultrasound in the follow-up of patients undergoing surgery for differentiated thyroid carcinoma.

SUBJECTS: The study included 89 patients (70 women and 19 men) with differentiated thyroid carcinoma (76 papillary and 13 follicular cancer).

METHODS: High-frequency ultrasound (US) was used in the evaluation of 89 subjects who underwent surgery for thyroid carcinoma. Fine-needle aspiration was performed in cases with positive US. In addition, determinations of thyroglobulin (Tgb) in serum, scintigraphy with 131I, and cervical palpation were evaluated. We determined sensitivity, specificity, and overall accuracy for each of these diagnostic methods.

RESULTS: Ultrasonography was positive in 22 subjects, 16 in the nodal area and 6 in the thyroid bed. Twenty-two subjects received fine-needle aspiration with US control; 13 (59%) of 22 were positive for cancer. The results of the US for detecting neoplastic disease showed a sensitivity of 65%, specificity of 86%, and overall accuracy of 82%. The overall accuracy for scintigraphy was 88% and for Tgb, 91%.

CONCLUSION: We concluded that US can be included in the follow-up protocol for patients undergoing surgery for differentiated cancer of thyroid, as a valuable tool to localize the recurrence. This technique is particularly useful in the evaluation of patients who are found to have elevated Tgb levels.

The treatment of differentiated thyroid cancer includes surgery and, in some cases, the ablation of residual thyroid tissue with therapeutic doses of iodine 131I. 1 The posttreatment search for recurrence or metastases is based on periodic body scanning with 131I and determination of serum thyroglobulin (Tgb) levels. 2,3

High-resolution ultrasound (US; 10 MHz) has been found to have a high sensitivity in diagnosing nonpalpable cervical masses. 4–6 Thus the possibility exists that including it in the protocols for follow-up of differentiated thyroid cancer may be valuable.

The aim of our study was to assess the value of high-resolution US (associated with directed fine-needle aspiration [FNA] biopsy) in the follow-up of patients undergoing surgery for papillary and follicular thyroid cancer.

Value of combined technetium-99m hydroxy methylene diphosphonate and thallium-201 imaging in detecting bone metastases from thyroid carcinoma

Detectability of bone metastases from differentiated thyroid carcinoma by technetium-99m hydroxymethylene diphosphonate ([99m]Tc-HMDP) bone scan is considered to be poor. Thallium-201 (201Tl) is also widely used for detecting metastatic lesions. Our present study was aimed at the evaluation of the combined use of (99m)Tc-HMDP and 201Tl imaging in successful detection of bone metastases from differentiated thyroid carcinoma. Twenty-seven thyroidectomized thyroid cancer patients (19 females, 8 males; 12 papillary type, 15 follicular type) with 77 bone lesions were included in this retrospective study. All of these patients received ablative doses of radioiodine. Thyroidal origin of the lesions was proved by positive iodine-131 (131I) uptake. In 131I-negative lesions, histological proof or absence of tumor markers other than thyroglobulin was considered when computed tomography (CT) and/or magnetic resonance imaging (MRI) suggested metastatic nature of the lesions. Of the 77 lesions, 58 (75.3%) were positive and 19 were negative in the (99m)Tc-HMDP bone scintigraphy, whereas 53 lesions (68.9%) could be detected by 201Tl scintigraphy. However, within the 19 (99m)Tc-HMDP-negative lesions, 14 showed abnormal accumulation of 201Tl, and within the 24 201Tl negative lesions, 19 were positive in (99m)Tc-HMDP scan. This resulted in a combined sensitivity of 93.5%. Our present study concludes that combined (99m)Tc-HMDP and 201Tl imaging is a sensitive and effective method for detecting bone metastases from thyroid carcinoma.

The predictive value of serum thyroglobulin in the follow-up of differentiated thyroid cancer

A strict and careful strategy has to be adopted to cure thyroid cancer. Diagnostic iodine-131 whole-body scan (WBS) and serum thyroglobulin (Tg) are important tools to detect thyroid remnants after thyroidectomy and radioiodine therapy. The aim of this retrospective study was to compare the relative sensitivity of WBS and Tg in the detection of thyroid remnants or metastases and to evaluate the predictive value of Tg in the clinical and scintigraphic course of the disease. Ninety-three patients were followed up after total thyroidectomy and the administration 4-6 weeks later of an ablative dose of 100 or 150 mCi 131I. Eighty-five percent of the patients were free of regional or distant metastases. The follow-up scheme included clinical examination of the patient followed by WBS, Tg, thyroid-stimulating hormone and free thyroxine measurements performed 4 weeks after thyroxine withdrawal and the observance of a low-iodine diet for at least 1 week. WBS (+) patients received a 100- or 150-mCi therapeutic dose of 131I. All patients were further followed up in the same way every 6 months until both WBS and Tg became negative, and thereafter at 1-, 2- and 4-year intervals. Six months after the postoperative radioiodine treatment (first visit), the sensitivity of WBS and Tg was 87% and 26% respectively. Among patients who were WBS(+) at the first visit, 95% of those who were Tg(-) and 47% of those who were Tg(+) had become disease-free at a median of 4 years after surgery (chi2=13.6; P<0.05). Patients whose tests were both positive required more radioiodine to be cured (335+/-90 vs 250+/-95 mCi; P<0.05). Our data indicate that in early diagnosed thyroid cancer, serum Tg measured 6 months after the postoperative 131I ablative dose is less sensitive than WBS for the demonstration of persistence of residual thyroid tissue but provides predictive information on the disease course. WBS(+) and Tg(-) patients are cured earlier and with less radioiodine than those who remain Tg(+).

131I therapy for elevated thyroglobulin levels

Assuming that the fractional uptake is the same, both after the administration of a diagnostic and a therapeutic activity, 131I uptake too low to be detected with 2-5 mCi may become detectable after the administration of 100 mCi. This should be performed routinely in patients with thyroglobulin levels above approximately 5 ng/mL during L-Thyroxine (LT4) treatment or 10 ng/mL off LT4 treatment for three main reasons: 1) in 80% of these patients, a post-therapy 131i total body scan showed foci of uptake in the neck or at distant sites, whereas in the other patients, metastases emerged clinically some years later; 2) 131I is not the only treatment modality, and, for instance, lymph node metastases may warrant further surgery; and 3) from a dosimetric point of view, the relevant parameter is the concentration of 131I, i.e., the ratio between the uptake and the mass of functioning tissue: a low uptake in a small metastasis may result in a higher 131I concentration than a higher uptake in a much larger metastasis.

Factors that Predict Metastasis of Papillary and Follicular Thyroid Cancers in Taiwan

The purpose of this study is to explore the relationship of postoperative thyroglobulin level and other clinical factors with tumor metastasis. Analysis of 281 pathologic lesions verified patients with papillary and follicular thyroid cancer who received their primary treatment at Chang Gung Memorial Hospital. Clinical information—including postoperative thyroglobulin levels, age, sex, primary tumor size, clinical staging, surgical methods, surgical findings, chest x-ray findings, and 131I uptake—were stored in the computer. Actual survival rate and univariate and multivariate analyses of these factors with the relationship of distant metastases were undertaken. Twenty-three patients in this study died of distant metastases from the thyroid cancer. Of these patients, 30.4% were older than 60 years. In contrast only 8.5% of patients in the survival group were older than 60 years (p < 0.05 in χ 2 ). All of the papillary thyroid cancer patients with distant metastases displayed thyroglobulin levels higher than 25 ng/ml, but only 24% (41 of 173 cases) of those without distant metastases had thyroglobulin levels higher than 25 ng/ml. In 12 follicular thyroid cancer patients with distant metastases, 11 patients' serum thyroglobulin levels were higher than 25 ng/ml. In contrast, only 7 of 33 patients with follicular thyroid cancer without distant metastases displayed similar thyroglobulin levels. Univariate analysis revealed that age, postoperative thyroglobulin levels, chest x-ray findings, pathologic type, and tumor size are associated with distant metastases. One-month postoperative serum thyroglobulin level could be used as a prognostic factor for papillary and follicular thyroid cancer patients with distant metastases.

Clinical presentations and treatment for 74 occult thyroid carcinoma. Comparison with nonoccult thyroid carcinoma in Taiwan

There is limited clinical information of Chinese patients with occult well-differentiated thyroid cancer (OTC). The purposes of this study were to elucidate the clinical presentations and results of treatment in the patients with OTC in Taiwan. The data of 568 patients with pathologically verified papillary and follicular thyroid carcinomas who received primary treatment in Chang Gung Memorial Hospital were retrospectively reviewed. Seventy-four of 568 patients with well-differentiated thyroid carcinoma were OTC; those included 71 papillary thyroid carcinomas and three follicular carcinomas. Among the 74 OTC patients, five cases (6.8%) presented with distant metastases, but 41 cases (10.1%) were found with distant metastases in 416 nonoccult thyroid cancer (NOTC) (p = 0.509). In the five OTC with distant metastases, there were three papillary carcinomas and two follicular carcinomas. Only one case (1.4%) died of distant metastasis of the occult papillary thyroid carcinoma versus 20 cases out of the total 568 (4.1%) well-differentiated thyroid carcinomas. After statistical analysis, there were no differences between the survival rates of OTC and NOTC patients. In the present study, 1 month postoperative serum thyroglobulin level could be used as prognostic factor in both OTC and NOTC patients. Only 54.17% of OTC patients were diagnosed as thyroid cancer by thyroid ultrasonography with the fine needle aspiration cytology. In conclusion, most OTC had relatively benign clinical courses, but distant metastases may result in mortality still observed. Therefore, OTC should be treated as NOTC, since relatively high rate of distant metastases were found in the patients with OTC.

Thyroid cancer in children, pregnant women, and patients with Graves' disease

Differentiated thyroid cancer may have a different clinical course when it develops in children, pregnant women, and patients with Graves' disease. Thyroid nodules which develop in these patients appear to have a greater risk of malignancy and should be evaluated aggressively. Treatment in all cases includes operation followed by radioactive iodine ablation (in the nonpregnant patient) and thyroid hormone suppression. Follow-up, including serum Tg and yearly thyroid scans, should be continued as long as possible.

Thyroglobulin: A Clinical Review

The introduction of the new assays for thyroglobulin (Tg) with a sensitivity of 1 to 3 mg/L has made it unnecessary to terminate thyroxine suppression therapy to determine Tg level. Thyroid-stimulating hormone should always be assessed in conjunction with the Tg to ensure that it is not high; as long as it is suppressed to normal, subnormal suppression is unnecessary. A total thyroidectomy is not a prerequisite for using Tg as a tumor marker; the Tg is equally reliable in those patients who have undergone a near-total or a subtotal thyroidectomy. Even patients who have undergone only a lobectomy may benefit from Tg monitoring if the level is low; however, an initial high Tg level (without a previous low Tg value) should not be interpreted as suggestive of cancer. Postoperative 131 I ablation is not necessary for an accurate Tg measurement. The finding of anti-Tg antibodies in patients with thyroid cancer remains a major problem, but other technical problems related to the absence of an international Tg standard have now been eliminated. Monitoring the Tg level reliably detects early recurrent disease in patients who have undergone a surgical procedure for thyroid carcinoma and are receiving thyroxine suppression therapy. Only those patients with Tg levels that exceed 3 to 5 mg/L or with clinical evidence of recurrence need to discontinue thyroxine treatment and have a 131 I scan. This approach can substantially decrease the expense, inconvenience, and morbidity of performing routine scans on these patients.

Advances in the management of patients with thyroid disease

Discoveries related to thyroid immunology, especially concerning the thyroid-stimulating hormone (TSH) receptor, may facilitate new immunologic approaches to the therapy of Graves' disease and the thyroiditis syndromes. Advances in genetics are being applied to the thyroid hormone resistance syndromes and papillary and medullary carcinomas. The development of ever more sensitive TSH assays has led to the detection of subclinical thyroid disease, which has special implications for the sick and elderly patients. Sensitive TSH assays also allow more precise titration of levothyroxine (T4) dosages, especially for patients with a past history of thyroid cancer. Evidence continues to accumulate suggesting that postmenopausal women on T4 doses that suppress the TSH level below 0.1 ulU/mL have lower bone mineral density than matched patients with healthy TSH levels. Also, pregnant hypothyroid women need higher T4 doses to normalize the TSH levels. In the evaluation of thyroid nodules, fine-needle aspiration biopsy is the single most definitive modality in selecting the patients for surgery. Scintigraphy provides a complimentary role, especially in defining autonomously functioning thyroid adenomas (AFTA), because these should not be treated with T4 suppression. Ultrasound-guided needle biopsy is occasionally helpful with nodules that are difficult to palpate. Concern for possible tracheal compression after treatment of toxic multinodular goiter with large doses of radioactive iodine (I-131) in the range of 50 to 150 mCi (1.85 to 5.5 GBq) does not seem warranted. Work, primarily out of Italy, suggests AFTA can be ablated with repeat ethanol injections. Residual tissues after thyroidectomy for differentiated carcinoma can be "stunned" by tracer doses of 131I greater than 3.0 mCi (111 MBq), which diminishes the uptake and effectiveness of a subsequent therapy dose. Positron emission tomograph, imaging with thallium-201, and Technetium 99m Sestamibi can identify a small number of patients shown to have metastases from differentiated thyroid carcinoma by increasing thyroglobulin levels in the absence of 131I uptake. Several groups have recently advocated treating such patients empirically with 131I.

Comparison of membrane proteins from benign and malignant human thyroid tissues by two-dimensional polyacrylamide gel electrophoresis

In this study two-dimensional (2D) polyacrylamide gel electrophoresis with silver staining was used to analyze cellular membranous proteins of various normal and pathological human thyroid tissues. The aim was to understand the differences in cellular membranous proteins between these tissues, which would aid in the differential diagnosis of thyroid malignancy. Characteristic protein spots had a molecular mass of 50-64 kDa and a pI of 5.7-6.5. There were two groups of isoform protein spots in this area. The higher-molecular-mass group was found in follicular thyroid cancer tissues which and was not visible in normal thyroid tissues. The low-molecular-mass group was found in follicular carcinoma or adenoma tissues and was detected in one to three spots. The papillary thyroid carcinoma tissues gave different 2D gel maps. There were few spots of papillary thyroid carcinoma tissue membranous proteins within the examined area. The 2D gel maps may be used for differential diagnosis of follicular neoplasm. The characteristics of these protein spots require further investigation.

Thyroid cancer treated in Chang Gung Memorial Hospital (northern Taiwan) during the period 1979-1992: clinical presentation, pathological finding, analysis of prognostic variables, and results of treatment

This study is a retrospective analysis of 248 thyroid cancer patients who received their primary treatment in the Chang Gung Memorial Hospital during the period January 1979 to December 1992. Among these cases, there were 173 papillary thyroid cancers (69.8%), 52 cases of follicular thyroid cancer (21%), 7 cases of medullary thyroid cancer (2.8%), and 16 cases of anaplastic thyroid cancer (6.5%). The subjects included 184 female patients with a mean age of 40.7 +/- 14.3 years and 64 males patients with a mean age of 49.2 +/- 14.3 years. Most of the cases had a nearly total thyroidectomy after the diagnosis was confirmed by frozen section during the operation. During the follow-up period, 19 (8.2%) patients diagnosed with well-differentiated thyroid cancer died of thyroid cancer in contrast to 12 patients (75%) with anaplastic thyroid cancer. The 1-year Greenwood survival probabilities after the disease is diagnosed in papillary, follicular, and anaplastic thyroid cancer are 0.98, 0.86, and 0.25, respectively. For the analysis of prognostic variables in well-differentiated thyroid cancer patients, 16 factors were entered for univariate and multivariate analysis. Using a log-rank univariate analysis, survival was significantly associated with the cell type of the primary tumor, age, clinical staging, postoperative 131I pattern, tumor size, postoperative thyroglobulin (Tg) level and postoperative x-ray results. In the Cox multivariate regression analysis the combination factors that gave the best prognostic value were the association of x-ray finding (P = .004), age (P = .017), and Tg level (P = 0.19). In conclusion, thyroid cancer is not an unusual disease in Taiwan. As previously reported anaplastic thyroid cancer has a poor prognosis. In this limited period of follow-up study, the patients' age with postoperative first positive x-ray finding and Tg level may provide the prognostic factors for patients with well-differentiated thyroid cancer.

Effect of postoperative 131I treatment on thyroglobulin measurements in the follow-up of patients with thyroid cancer

Correlation of serum thyroglobulin (Tg) levels with recurrent cancer was performed in 200 patients who had undergone a subtotal thyroidectomy for well-differentiated thyroid carcinoma. Patients were divided into three groups: (1) those not treated postoperatively with radioactive iodine, (2) those treated with low dose (30 mCi) radioactive iodine, and (3) those treated with high dose (50-250 mCi) radioactive iodine. Tg levels proved to be reliable in detecting recurrent thyroid cancer regardless of the dose of radioactive iodine given postoperatively. These results reinforce the recommendation of using the Tg assay as the primary method of following these patients postoperatively, even when there was less than a total thyroidectomy and ablation with radioactive iodine.

Management of patients with differentiated thyroid cancer who have positive serum thyroglobulin levels and negative radioiodine scans

Most current evidence suggests that patients with papillary or follicular thyroid cancer after total thyroidectomy who are Tg positive (Tg > or = 10 ng/mL) and radioactive iodine scan negative warrant treatment with 100 mCi of 131I with a follow up scan and Tg determination. If isolated focal metastatic deposits are present they should be resected before treatment with radioiodine. Although some physicians might recommend radioiodine treatment only for high risk patients, we would recommend it for all patients with elevated serum Tg levels that increase after TSH stimulation, or until further information becomes available to support a different approach.

The role of iodine-131 and thallium-201 imaging and serum thyroglobulin in the management of differentiated thyroid carcinoma

BACKGROUND

A prospective study was conducted to evaluate the use of iodine-131 sodium scintigraphy, thallium-201 chloride scintigraphy, and quantitative serum thyroglobulin estimation in the detection of differentiated thyroid carcinoma after thyroidectomy and iodine-131 sodium ablative therapy.

METHODS

Thirty-one patients with a median age of 45.6 years (range, 20-73 years) were included in the study. After optimal endogenous thyroid-stimulating hormone stimulation (> 50 mU/ml), 53 pairs of iodine-131 and thallium-201 scans were performed. Concomitant serum thyroglobulin levels were available for 32 pairs of scans. The presence or absence of thyroid cancer was established by clinical, radiologic, and/or biopsy findings.

RESULTS

The concordance between iodine-131 and thallium-201 scan findings in the presence of disease (25 scan sets) was 36%. The concordance in the absence of disease (28 scan sets) was 82%. Iodine-131 scanning was found to be significantly better (P < 0.05) than thallium-201 scanning, in terms of sensitivity (0.8 versus 0.6), specificity (0.96 versus 0.82), accuracy (0.89 versus 0.72), and the predictive value of a positive test (0.95 versus 0.75). The measurement of serum thyroglobulin had a low sensitivity (0.3) in the study but had a specificity of 1.0.

CONCLUSION

It was concluded that iodine-131 sodium scintigraphy is superior to thallium-201 scintigraphy and serum thyroglobulin estimation for the detection of residual or metastatic differentiated thyroid carcinoma. However, the use of combined modalities provides a higher diagnostic yield. Thallium-201 scintigraphy was especially useful in cases in which iodine-131 scintigraphy was negative and quantitative thyroglobulin levels were elevated.

False positive 131I total body scan due to an ectasia of the common carotidis

A cervical accumulation of radioiodine at Total Body Scan (TBS) in a patient who had been thyroidectomized for a follicular thyroid carcinoma led to unnecessary radioiodine treatment. Thyroglobulin measurements indicated constantly low levels. Following ultrasound scanning of the neck, echo-doppler examination of the cervical vessels and angiography with 99Tc, this area of increased activity at TBS imaging was shown to be due to an ectasia of the right common carotidis causing blood stasis and reverse flow.

Clinical use of tumor markers in oncology

The perfect tumor marker would be one that was produced solely by a tumor and secreted in measurable amounts into body fluids, it should be present only in the presence of cancer, it should identify cancer before it has spread beyond a localized site (i.e., be useful in screening), its quantitative amount in bodily fluids should reflect the bulk of tumor, and the level of the marker should reflect responses to treatment and progressive disease. Unfortunately, no such marker currently exists, although a number of useful but imperfect markers are available. The predominant contemporary markers are discussed here by chemical class, as follows: glycoprotein markers, including carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), beta-human chorionic gonadotropin (beta-hCG), and prostate specific antigen (PSA); mucinous glycoproteins, including CA 15-3, CA 19-9, mucinous-like cancer antigen and associated antigens, and CA 125; enzymes, including prostatic acid phosphatase (PAP), neuron specific enolase (NSE), lactic acid dehydrogenase (LDH), and placental alkaline phosphatase (PLAP); hormones and related endocrine molecules, including calcitonin, thyroglobulin, and catecholamines; and, molecules of the immune system, including immunoglobulins and beta-2-microglobulin. The biologic properties of each group of tumor markers are discussed, along with our assessment of their role in clinical medicine today.

A new immunoradiometric assay (IRMA) system for thyroglobulin measurement in the follow-up of thyroid cancer patients

A new commercially available kit for thyroglobulin (Tg) measurement [immunoradiometric assay (IRMA) system based on monoclonal antibodies] was used in 479 patients with thyroid carcinoma. The effective working range was 1 ng/ml, and results were strongly correlated with our homemade radioimmunoassay (RIA). This IRMA method is less susceptible to interferences of auto-antibodies than our RIA. During thyroxine (T4) treatment, the Tg level was undetectable in 98% of patients after total thyroid ablation, in 91% after total thyroidectomy and in 42% after lobectomy only. In this situation, Tg was found in all patients with large metastases and in 88% of those with small metastases. Following T4 withdrawal, Tg was detectable in all patients with neoplastic disease and in 13% of those in complete remission after total thyroid ablation. In conclusion, Tg measured with this IRMA method appears to be a reliable marker of differentiated thyroid carcinoma.

Effective laboratory evaluation of thyroid status

This article focuses on recent developments in thyroid-related laboratory tests, including analytical methods, clinical utility, and limitations of TSH, FT4, T4, FT3/T3, thyroglobulin, and thyroid autoantibodies and the effective use of these tests in the diagnosis of various forms of hypothyroidism or hyperthyroidism, and the management of patients undergoing T4 replacement, T4 suppression, or antithyroid drug therapy.

Usefulness of the combined antithyroglobulin antibodies and thyroglobulin assay in the follow-up of patients with differentiated thyroid cancer

A total of 1050 patients with differentiated thyroid cancer (DTC) have been followed in the Thyroid Center of Padua by means of serum thyroglobulin (Tg) measured with IRMA method and anti-Tg antibodies (TgAb) assays. Circulating TgAbs were detected in 102 (9.7%) patients. In 32 of these 102, TgAbs were evaluated before and after total thyroidectomy and 131I ablation. In these patients no relationship was found between preoperative serum TgAb levels on the one hand and tumor stage at diagnosis or outcome of the disease on the other. During the follow-up, TgAb serum levels decreased or disappeared in 21 cases considered tumor-free, while they remained unchanged or even increased, in comparison with the preoperative ones, in 11 patients, 5 with proven metastases and 6 considered tumor-free. Evaluating the whole group of 102 TgAb-positive patients, we observed that TgAb serum levels, measured after thyroid ablation, were significantly higher in cases with metastases than in those considered tumor-free (653.0 +/- 196.9 vs 157.7 +/- 116.5 U/ml, m +/- SD, p less than 0.0001). In the group of patients with metastases and circulating TgAbs, Tg serum levels were elevated in 27% of cases on TSH-suppressive therapy and in 44% off therapy when nodal metastases were present, and in 67% of cases on TSH-suppressive therapy and in 83% off therapy when distant metastases were present.(ABSTRACT TRUNCATED AT 250 WORDS)

Histochemical determination of iodide peroxidase activity in various thyroid disorders

We developed a histochemical method to demonstrate iodide peroxidase activity in various thyroid disorders and compared it with the biochemical and ultrastructural-cytochemical methods. All of the 26 adenomatous goiters and 43 follicular adenomas were peroxidase-positive. In the 74 cases of thyroid carcinomas examined, about half of the follicular carcinomas (17 of 33 patients), and a few papillary carcinomas (3 of 41 patients) were peroxidase-positive. Peroxidase-negative cases were seen in 70% (52 of 74 patients) of the follicular and papillary carcinomas. All the non-tumorous thyroid tissues adjacent to various disorders were peroxidase-positive. Since our histochemically demonstrated peroxidase activities almost parallel those determined biochemically and ultrastructural-cytochemically, we conclude that histochemical examination is a simple and useful method for the detection of peroxidase activity. As for the relationships between histochemically proved peroxidase activity and the histology of tumors, the histological differentiation of tumors was not consistent with their functional differentiation classified according to peroxidase activity.

Low levels of serum thyroglobulin after withdrawal of thyroid suppression therapy in the follow up of differentiated thyroid carcinoma

We evaluated the reliability of very low serum thyroglobulin (Tg) levels (less than 3 ng/ml) obtained after withdrawal of thyroid suppression therapy in 224 patients without anti-Tg antibodies, who had undergone total thyroidectomy (125 patients) or thyroidectomy followed by 1 or more courses of 131I therapy (99 patients), by performing whole body scans after a therapeutic course of 131I given at the same time of Tg measurement. In 79 patients (35%) a positive scan, associated with a very low level of Tg, was noted. The 131I uptake was limited to the thyroid bed in 60 patients, but metastases were demonstrated in 19 patients (8.5%). These results are mainly explained by the much improved performance of scintigraphy after administration of therapeutic doses of 131I. In the majority of patients, especially those whose 131I uptake was limited to the thyroid bed, further scans were negative. Therefore, in these cases, negative Tg values can generally be considered an early indication of satisfactory evolution. However, in 8.5% of all cases, very low Tg levels were associated with metastases. Thus the follow up of thyroid cancer should not rely only upon Tg determination, even after suppression therapy withdrawal.

Clinical evaluation of serum thyroglobulin measurement using a commercial kit in the diagnosis of recurrent thyroid cancer

The value of serum thyroglobulin assay employing a kit manufactured by Diagnostic Products Corporation in the detection of recurrence of thyroid carcinoma in patients treated by thyroidectomy and ablative therapy was assessed by clinical follow-up and radioiodine scanning of 122 patients over a 2-year period. A total of 204 specimens were analysed. The assay was found to be sensitive and highly specific for the detection of recurrent thyroid carcinoma provided that lipemic sera are clarified by ultracentrifugation prior to measurement and that results from those patients who demonstrate positive serum antithyroglobulin antibodies are excluded. The predictive value of a serum thyroglobulin level above 20 pmol/L was 96% for recurrence of thyroid carcinoma. The predictive value for non-recurrence was 98% for serum thyroglobulin levels below 10 pmol/L. The specificity and sensitivity of the assay were poor for serum thyroglobulin levels between 10 and 20 pmol/L. In recurrence-free patients, the serum thyroglobulin levels were not changed by withdrawal of thyroid replacement therapy 4-7 weeks prior to sampling.

Immunoreactive thyroglobulin in sera and saliva of patients with various thyroid disorders: role of autoantibodies

The present study was designed to assess the transfer of thyroglobulin (Tg) and anti-Tg antibodies (TgAb) to saliva in subjects with positive TgAb in their sera. Group I consisted of normal euthyroid control subjects (n = 10). Group II were patients with various thyroid disorders and no TgAb in their sera (n = 6). Group III were patients with thyroid disorders and TgAb in their sera (n = 31). The mean serum Tg level (+/- SE) and mean TgAb level [mean % binding +/- SE (range)] were as follows: Group I, Tg: 22.0 ng/ml +/- 1.64 (n = 10); TgAb 1.91% +/- 0.34 (range 0.6% to 4%). Group II, Tg: 119.8 ng/ml +/- 28.0 (n = 6) TgAb 1.59% +/- 0.34 (0.64% to 2.7%). Group III Tg 167.9 ng/ml +/- 41.0 (n = 31) TgAb 23.2% +/- 3.87 (4.2% to 67.5%). The mean salivary Tg level (SaTg) and mean TgAb binding (% +/- SE range) in saliva were as follows: Group I SaTg 2.07 ng/ml +/- 0.39 (n = 10) SaTgAb 1.13% +/- 0.38 (0% to 3.1). Group II SaTg 3.41 ng/ml +/- 0.67 (n = 6), SaTgAb 0.55% +/- 0.29 (0-1.9%). Group III SaTg 5.22 ng/ml +/- 0.96 (n = 31), SaTgAb 3.1% +/- 1.58 (0 to 47.7%). Salivary TgAb were only present in 4 out of 31 cases of Group III. Mean serum Tg in group IV-A was 75.01 ng/ml +/- 52.1 (n = 11). Mean serum TgAb in group IV-A was 1.94% +/- 0.31 (n = 11).(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroid nodules and thyroid cancer--diagnostic aspects

The clinical evaluation of patients with thyroid nodules is a common problem confronting the clinician. The vast majority of such nodules are benign, but concern that such a thyroid swelling may harbour malignancy demands prompt and accurate diagnosis. Furthermore, it is clear that properly treated differentiated thyroid carcinoma is associated with an excellent prognosis. The objective of investigating patients presenting with thyroid nodules is to define the small number of malignancies with minimum inconvenience to the patient in the most cost-effective way. There are no laboratory tests which reliably differentiate benign from malignant disease. The traditional approaches of radionuclide and ultrasound scanning have been shown to be poorly specific in the diagnosis of malignancy, resulting in many unnecessary operations for benign lesions. These tests have been replaced in many centres by fine needle aspiration cytology, with surgery for abnormal cytological findings alone. This technique is easily performed in an out-patient clinic and is well tolerated; accuracy in the diagnosis of thyroid neoplasia of up to 97% can be achieved.

Clinical evaluation of tumor characteristics predisposing serum thyroglobulin to be undetectable in patients with differentiated thyroid cancer

This study delineates tumor characteristics which predispose serum thyroglobulin (TG) to be undetectable in patients in spite of persistent or recurrent differentiated thyroid cancer. Three hundred seventy four thyroid carcinoma patients with completed thyroid ablation were investigated by means of conventional diagnostic procedures (131 iodine total-body scan, x-ray, TG determination) and, in addition, with high-resolution sonographic study of the neck. Sensitivity of TG for the detection of metastases amounted to 83% under TSH stimulation and 50% under thyroxine (T4) treatment. Specificity proved to be 95% under TSH stimulation and 99% under T4 treatment. Common features of the tumors associated with false-negative TG determinations (n = 16) were papillary histologic characteristics, manifestation in lymph nodes of the neck or mediastinum, and small size. It is therefore necessary for the early detection of persistent or recurrent papillary cancer metastases to perform in addition to 131 iodine scans high-resolution sonography of the neck in combination with the determination of TG serum concentrations under endogenous TSH stimulation.

Follow-up of patients with differentiated thyroid carcinoma. Experience at Institut Gustave-Roussy, Villejuif

The recent introduction of sTSH assays allows for a definite control of the inhibition of TSH secretion. Clinical examination and serum thyroid hormone measurements are necessary to obviate hyperthyroidism. Relapses may occur after decades of apparent complete remission. Follow-up should be pursued throughout the patient's lifetime. Two specific means allow the detection of relapses at a stage when X-rays are still normal: measurement of serum thyroglobulin and 131I total body scan. Their combined use is recommended.

Serial serum thyroglobulin measurements in the management of differentiated thyroid carcinoma

Serum thyroglobulin (Tg) was measured on repeated occasions in 416 patients with differentiated thyroid cancer for up to 7 years after initial therapy. All patients had thyroidectomy and/or ablative 131I therapy and all measurements were done while patients were receiving T4 replacement. Tg was measured using a double-antibody radioimmunoassay. Overall correlation between serum Tg concentration and presence or absence of cancer was 95.9%. At the time of initial measurement 295 patients had serum Tg less than 5 micrograms/l, and in latest analysis only 1.7% of these patients showed evidence of disease. Initially there were 19 patients of a total of 121 with serum Tg greater than 5 micrograms/l in whom no cancer was apparent. In eight of these 19 subjects recurrent or metastatic disease has been diagnosed up to 3.5 years after the first measurement indicating that in these cases serum Tg values were 'predictive'. Serum Tg appears to be a sensitive and specific means of detecting residual, recurrent or metastatic thyroid cancer and in most situations can replace routine, expensive and inconvenient radioactive thyroid scans; these should be performed when serum Tg values are elevated or when there is clinical evidence suggesting recurrence.

Increased heterogeneity of serum thyroglobulin in thyroid cancer patients as determined by monoclonal antibodies

We investigated the immunological heterogeneity of plasma Tg in thyroid cancer patients using monoclonal antibodies in an immunoradiometric assay and a conventional RIA system with a polyclonal rabbit antibody. The results were compared with measurements of plasma Tg in patients with nonmalignant disease. We can demonstrate an increased immunological heterogeneity in tumor patients compared with patients with non-malignant thyroid diseases. In one case the Tg value measured by a monoclonal test system exceeded the value obtained by a polyclonal RIA system in the same sample by a factor of 25. It has to be further investigated whether this increase in heterogeneity is of diagnostic value in the follow-up of thyroid cancer patients.

Thyroglobulin production by malignant thyroid tumors. An immunocytochemical and radioimmunoassay study

Four hundred thirty surgical and biopsy specimens of malignant thyroid tumors of 323 patients were analyzed by histologic and immunocytochemical examination for their thyroglobulin (TG) content. Almost 95% of the differentiated thyroid carcinomas of follicular origin contained immunoreactive TG. The authors could not demonstrate TG in anaplastic carcinomas. Postoperative follow-up and serum TG determinations were available for 111 athyroid patients. Serum TG was elevated in five patients with metastatic or recurrent moderately differentiated follicular carcinoma, in two patients with metastasizing papillary, and in one patient with anaplastic carcinoma. Four patients had detectable serum TG levels without clinical and radiologic evidence of recurrence or metastases. In addition to conventional histologic examination, immunocytochemical demonstration of TG is a reliable and valuable aid in the diagnosis, classification, and determination of the grade of differentiation of malignant thyroid tumors. From this the pathologist can provide a pathologic basis for postoperative patient management.

Critical evaluation of serum thyroglobulin (Tg) levels during thyroid hormone suppression therapy versus Tg levels after hormone withdrawal and total body scan: results in 291 patients with thyroid cancer

Serum thyroglobulin (Tg) levels were measured during thyroid-hormone suppressive therapy in 291 patients who had been treated for well-differentiated thyroid carcinoma. The findings were compared with those of a subsequent total body scan (TBS) and with Tg levels measured after thyroid-hormone withdrawal. Of the patients with low Tg levels during suppressive therapy, 91.6% were subsequently shown to be free of disease or to have only remnants in the thyroid bed, whereas 8.4% had metastases (false-negative). Of the patients with false-negative findings, 89.3% had nodal metastases; 60.8% of the patients with nodal metastases exhibiting radioiodine uptake and only 23% of those with nonfunctioning nodal metastases had low Tg levels during suppression therapy. After thyroid-hormone withdrawal, all but 1 of the patients with nodal metastases had high Tg levels. All but 2 of the patients with distant metastases had high Tg levels during suppression therapy; 1 of these 2 patients exhibited high Tg levels after T3 withdrawal. No differences between Tg levels in patients with functioning and non-functioning metastases were found. Our study indicates that Tg assays performed during suppressive therapy have a fairly good predictive value and can be used as a general guide in the follow-up of thyroid cancer. However, since most differentiated metastases produce Tg only when stimulated by thyroid-stimulating hormone, measurements of Tg levels after the discontinuation of suppressive therapy would also seem to be necessary.

Influence of initial large dose on subsequent uptake of therapeutic radioiodine in thyroid cancer patients

Fifty-two patients with differentiated thyroid cancer, following thyroidectomy were studied by administering a quantity of up to 5 mCi of [131I]sodium iodide. In most of these patients, radioiodine uptake values obtained with the subsequent therapeutic dose were markedly lower than those observed with the initial doses. This observation was verified in seven of the patients with differentiated thyroid cancer, by measuring the radioiodine uptake with a second dose of 4.5 mCi of [131I]sodium iodide. Calculations showed that the major etiology was probably therapeutic irradiation of the thyroid by the first dose.

The effect of [125I]thyroglobulin tracer heterogeneity on serum Tg RIA measurement

Comparative serum Tg RIA studies were used to evaluate the contamination of 125I-19S Tg (B) (670 000 Da) with a smaller partially immunoactive degradation product (C) (530 000 Da). B and C tracers prepared either by enzymic (GO), chloramine T (CT) or Bolton Hunter (BH) iodination methods were tested. B tracers, (either GO or CT), gave consistently higher Tg values vs C tracers at serum Tg levels greater than 30 ng/ml. No difference in values was seen with C tracers of either GO, CT or BH origin. The immunological nonidentity between B and C tracers was shown by nonparallelism between diluted high Tg sera and the Tg RIA standards. Nonparallelism existed above 30 ng/ml with all C tracers irrespective of iodination method and was, in addition, present with CT-B tracers from 3/4 Tg preparations. Only B tracers, prepared by GO or BH, consistently showed adequate parallelism. The ubiquitous nature of C contamination of B tracers prompted a comparative study of serum Tg RIA values between four different laboratories. Good interlaboratory agreement was shown for Tg values less than 30 ng/ml, whereas there was a 10- to 20-fold difference in values for sera with high Tg levels (greater than 100 ng/ml). The observed/expected ratio of values, in serial dilutions of a high Tg sera, measured in two of the laboratories, suggested that nonparallelism accounted for some interlaboratory differences. Contamination of 125I-19S Tg (B) by its breakdown product C, has potential to lower absolute serum Tg values and produce non-parallelism in diluted high Tg sera which results in aberrantly low Tg RIA values. This problem potentially limits the clinical application and relevance of serum Tg measurements in thyroid cancer patients, especially those with metastases associated with high serum Tg levels.

Differentiated thyroid cancer in children

Differentiated thyroid cancer in children remains a controversial disease entity. Its incidence has markedly declined over the last decade since the use of radiotherapy in the treatment of benign conditions of the head, neck, and thorax was abandoned. Other etiologic factors have become relatively more important. The clinical presentation of childhood thyroid cancer is similar to that found in adults, except for a higher frequency of local and distant metastases at the time of initial diagnosis. The specificity and sensitivity of diagnostic tests are limited; however, like in adults, fine-needle aspiration compares favorably with other available diagnostic methods. The therapeutic approach to a child with thyroid cancer represents the most controversial issue associated with the disease. This review provides a discussion of the rationale for the different therapeutic options and emphasizes the excellent prognosis and survival rates, especially when patients are subjected to aggressive treatment with total thyroidectomy followed by the administration of radioactive iodine.

Diagnostic value of a single serum thyroglobulin determination on and off thyroid suppressive therapy in the follow-up of patients with differentiated thyroid cancer

To assess the significance of a single serum thyroglobulin (Tg) determination on and off thyroid suppressive therapy, serum Tg measurements have been performed in 349 serum samples from 82 patients with differentiated thyroid cancer. All samples were collected after total thyroidectomy with or without subsequent ablation of residual thyroid tissue by radioiodine. One hundred and fifty-three samples were obtained while the patients were on thyroid suppressive therapy and 196 after withdrawal of medication. The results of serum Tg assays were analysed in relation to the presence or absence of residual or metastatic thyroid tissue, as assessed by clinical and laboratory evaluation, including 131I whole body scan. In patients with thyroid residue but no metastases, undetectable serum Tg (false negative results) occurred in 45% of cases off therapy and in 92.9% of cases during therapy. In the presence of metastases no undetectable serum Tg result was found in patients off therapy, while four (6.9%) out of 58 samples from patients with bone and/or lung metastases and seven (31.8%) out of 22 samples from patients with lymph node metastases alone were undetectable (falsely negative) during suppressive therapy. Serum Tg was undetectable in sera from patients with no evidence of thyroid residue or metastatic disease in all but one (1.7%) of 59 samples on and three (5.4%) of 56 samples off suppressive therapy. These Tg results were confirmed to be truly rather than falsely positive, since evidence of metastatic disease was obtained by whole body scan after the administration of therapeutic doses of 131I.(ABSTRACT TRUNCATED AT 250 WORDS)

Chest computed tomography (CT) in patients with micronodular lung metastases of differentiated thyroid carcinoma

Forty thoracic CT scans have been performed on 27 patients with micronodular lung metastases of differentiated thyroid carcinoma. Lung nodules were visualized in 14 out of 19 patients (78%) with functioning lung metastases, although their chest X rays were normal. However, only a small number of peripheral micronodules can be visualized by CT scan since the central micronodules remain undistinguishable from adjacent vessel structures. A close relationship has been found between the number of micronodules and the thyroglobulin (Tg) serum level. In patients previously treated by 131I for proven lung metastases and who had no uptake for several years, but in whom Tg remained detectable in the serum, CT scans have shown micronodules in 7 of the 13 patients with normal chest X rays. The present data suggest that these nodules are mainly a result of fibrosis. CT scanning appears to be an important complementary tool with regard to 131I whole body scintigraphies in the radiologic diagnosis of lung nodules and in the assessment of radioiodine therapy.

Radionuclide diagnosis and therapy of thyroid cancer: current status report

Thyroid cancer is uncommon, with an incidence of 10,300 new patients each year and a mortality of 1,100 patients each year. Patient survival correlates with many factors, including tumor pathology, age, primary lesion size, distant metastases, extent of surgery, and radioiodine therapy. Deaths from thyroid cancer may occur many years after diagnosis, and such an indolent course has hampered the analysis of the multiple treatment programs advocated. Thyroid imaging continues to play an important role in the initial detection and follow-up management of thyroid cancer, but the search for a specific tracer for the primary lesion continues. The complementary role of serum thyroglobulin and radioiodine in the follow-up of the thyroidectomized patient is discussed. Radioiodine therapy has proven effectiveness in those patients with radioiodine-avid distant metastases and/or regional metastases. Whether radioiodine ablation of residual thyroid bed activity is beneficial remains controversial.

Correlation of thyroglobulin measurements and radioiodine scans in the follow-up of patients with differentiated thyroid cancer

Correlation of radioiodine (131I) scans and serum thyroglobulin (Tg) concentrations were performed in the follow-up of 85 differentiated thyroid cancer patients who had undergone total thyroidectomy. Tg results were also compared with the control group of 33 thyroidectomized patients with no evidence of thyroid carcinoma and normal values for Tg established. Excellent correlation between Tg and scans was noted in patients with scan evidence of metastasis distant from the neck. Poor correlation was present in patients with scan evidence of local neck metastasis only, thyroid bed activity, and those with mediastinal activity. In addition, in 8% of the patients, the Tg assay could not be performed because of interfering antibodies. The conclusion is that elevated Tg concentration is a good indicator of metastasis outside of the neck as detected by 131I scans. Caution should be used when Tg alone is used in evaluating local neck metastasis demonstrated on scans. The significance of mediastinal activity warrants further investigation.