Thyroglobulin may be undetectable in the serum of patients with metastatic disease secondary to differentiated thyroid carcinoma. Follow-up of differentiated thyroid carcinoma

Clinical Benefit of Radioiodine Administration in a Rare Case of Iodine Avid Thyroid Carcinoma with No Secretion of Thyroglobulin

Differentiated thyroid cancer (DTC) is the most common endocrine cancer and its outcome is usually favorable. Its basic treatment is well codified, but its monitoring is much less. The value of thyroglobulin (Tg) is one of the main elements for monitoring DTC, while the use of iodine scintigraphy is becoming less recommended. In this case report, we discuss a clinical situation where a patient presented differentiated thyroid metastatic lesions confirmed by biopsy, uptaking radioactive iodine, with undetectable levels of Tg (in the absence of autoantibodies). We discuss the various hypotheses explaining this clinical situation, the potential advantages of performing periodic iodine scintigraphy in some intermediate and high-risk patients and report the documented clinical benefit of radioiodine therapy.

The Diagnostic Usefulness of 131I-SPECT/CT at Both Radioiodine Ablation and during Long-Term Follow-Up in Patients Thyroidectomized for Differentiated Thyroid Carcinoma: Analysis of Tissue Risk Factors Ascertained at Surgery and Correlated with Metastasis Appearance

¹³¹I Single-photon emission computerized tomography/computerized tomography (SPECT/CT) in the management of patients thyroidectomized for differentiated thyroid carcinoma (DTC) was further investigated. Retrospectively, 106 consecutive DTC patients were enrolled at the first radioiodine ablation, 24 at high risk (H), 61 at low risk (L) and 21 at very low risk (VL). ¹³¹I whole-body scan (WBS) and SPECT/CT were performed after therapeutic doses using a hybrid dual-head gamma camera. At ablation, SPECT/CT correctly classified 49 metastases in 17/106 patients with a significantly (p < 0.001) more elevated number than WBS which evidenced 32/49 foci in 13/17 cases. In this case, 86/106 patients could be monitored in the follow-up including 13/17 cases with metastases already at post-therapeutic scans. SPECT/CT after radioiodine diagnostic doses more correctly than WBS ascertained disease progression in 4/13 patients, stable disease in other 4/13 cases and disease improvement in the remaining 5/13 cases. Further 13/86 patients with only residues at post-therapeutic scans showed at SPECT/CT 16 neck lymph node (LN) metastases, three unclear and 13 occult at WBS. Significant involvement of some tissue risk factors with metastasis appearance was observed, such as minimal extrathyroid tumor extension and neck LN metastases. These risk factors should be carefully considered in DTC patient follow-up where ¹³¹I-SPECT/CT routinely use is suggested as a support tool of WBS.

Undetectable or low (<1 ng/ml) postsurgical thyroglobulin values do not rule out metastases in early stage differentiated thyroid cancer patients

Background

Differentiated thyroid cancer (DTC) work-up is based on (near)total-thyroidectomy plus thyroid remnant ablation (TRA) with 131-radioiodine in many patients, and long-life follow-up. ¹³¹I-post therapy whole body scan (pT-WBS) and serum thyroglobulin (Tg) are used in identifying metastatic patients. Some authors have evaluated the possibility of using post-surgical Tg (ps-Tg) values in deciding for or against TRA. The aim of our study was to verify the diagnostic accuracy of ¹³¹I-pT-WBS and SPECT/CT imaging (post-therapeutic imaging) compared to serum Tg levels in detecting metastases in early stage of DTC patients.

Results

Post-therapeutic imaging revealed metastases in 82 out of 570 (14.4%) patients. Metastases were successively confirmed by other diagnostic tools or by histology (sensitivity and PPV = 100%). Seventy-three out of 82 patients (90.2%) showed ps-Tg levels ≤1 ng/ml. In fifty-four per cent of patients, serum Tg levels at TRA remained ≤1 ng/ml.

Conclusion

In conclusion, ps-Tg levels cannot be used in deciding for or against TRA. In early stage of DTC, post-therapeutic imaging (¹³¹I-pT-WBS and SPECT/CT) is an accurate method of detecting metastases, also in patients with stimulated serum Tg values ≤1 ng/ml

Methods

We retrospectively reviewed the records of 570 consecutive patients affected by pT1-pT3 DTC (F = 450, M = 120), referred to our Nuclear Medicine Units in the last five years to perform TRA after (near)-total-thyroidectomy.All patients underwent TRA 3-4 months after thyroid surgery either in euthyroid or in hypothyroid state. Serum Tg values evaluated in post-surgical period and at TRA were matched with post-therapeutic imaging results.

Undetectable pre-ablation thyroglobulin levels in patients with differentiated thyroid cancer: it is not always what it seems

OBJECTIVE

To establish the frequency of U Tg (undetectable pre-ablation thyroglobulin) in TgAb- negative patients and to evaluate the outcome in the follow-up.

SUBJECTS AND METHODS

We retrospectively reviewed 335 patients' records. Twenty eight patients (9%) had U Tg. Mean follow-up was 42 ± 38 months. All subjects had undergone total thyroidectomy, and lymph nodes were positive in 13 (46%) patients. Tg and TgAb levels were measured 4 weeks after surgery by IMA technology in hypothyroid state. No evidence of disease (NED) status was defined as undetectable (< 1 ng/mL) stimulated Tg and negative Tg-Ab and/or negative WBS, together with normal imaging studies.

RESULTS

Seventeen patients (61%) were considered with NED. Four patients (14%) had persistent disease (mediastinum, n = 1, lung n = 2, unknown n = 1), and 7 (25%) had detectable TgAb by other method during their follow-up.

CONCLUSIONS

U Tg levels usually is associated to a complete surgery. However, in a low percentage of patients, this may be related to false negative Tg or TgAb measurement.

Incidence and implications of negative serum thyroglobulin but positive I-131 whole-body scans in patients with well-differentiated thyroid cancer prepared with rhTSH or thyroid hormone withdrawal

AIMS

To evaluate the incidence and clinical implications of a positive whole-body I-131 scan but negative stimulated serum Tg/TgAb level following an ablative or diagnostic I-131 dose in patients with well-differentiated thyroid cancer and whether there is a difference in incidence if prepared with thyroid hormone withdrawal compared with rhTSH stimulation.

METHODS

I-131 scan findings, serum Tg/TgAb levels, TNM stage and method of thyroid tissue stimulation in 193 consecutive patients (138F, 55M) with well-differentiated thyroid cancer undergoing postoperative ablative I-131 therapy and 121 consecutive (94F, 27M) patients undergoing diagnostic I-131 surveillance scans were retrospectively reviewed. Comparisons of proportions were performed using Chi-square tests. Clinical, biochemical and I-131 scan follow-up data were obtained for each patient cohort.

RESULTS

39/193 (20·2%) postablative I-131 and 10/121 (8·3%) diagnostic I-131 patients had negative stimulated serum Tg/TgAb levels but positive I-131 scans for residual thyroid tissue. Nine (4·7%) of the postablative patients had I-131 uptake in the lateral neck suspicious for loco-regional metastatic disease. In the postablative I-131 group, 38/169 (22·5%) prepared with rhTSH compared to 1/24 (4·2%) prepared with thyroid hormone withdrawal were Tg/TgAb negative but I-131 scan positive (P = 0·04). Follow-up of 21/39 postablative I-131 patients with negative Tg/TgAb but positive I-131 scans confirmed a significant proportion of patients (4/21) (19·1%), remained Tg/TgAb negative/I-131 scan positive, some of whom had higher-risk disease at original diagnosis (2/4) (50%).

CONCLUSIONS

Our study confirms that in the setting of I-131 ablation therapy or diagnostic I-131 scanning, a significant proportion of patients (20·2% and 8·3%, respectively) have residual benign or malignant thyroid tissue on whole-body scanning despite a negative stimulated serum Tg level. Whether such patients who would otherwise be missed as having residual thyroid tissue on serum Tg testing alone have a worse clinical outcome remains uncertain. Our findings do however suggest performing both stimulated serum Tg/TgAb levels and I-131 scans for the follow-up of patients with higher-risk thyroid cancer may be important. There may also be a slightly higher incidence of this phenomenon in patients prepared with rhTSH rather than by thyroxine withdrawal.

Papillary microcarcinoma

Background

Papillary microcarcinoma (PMC) is increasing in incidence because of diagnosis by ultrasound-guided fine-needle aspiration cytology.

Methods

Between January 1966 and December 1995, we treated 6019 patients with papillary cancer; among them, 2070 patients with PMC were studied.

Results

PMC is essentially very similar to papillary cancer that is 11 mm or larger and has a very good prognosis. Smaller tumors and younger patients have a better prognosis. Among PMC, larger tumors (6–10 mm) recur in 14% at 35 years compared with 3.3% in patients with smaller tumors. Patients older than 55 years have recurrence in 40% at 30 years, with a worse prognosis than younger patients who have a recurrence rate of less than 10%. Extracapsular invasion by the primary tumor also has a higher recurrence rate. The majority of recurrences are in the neck. Therefore, annual ultrasound of the neck is effective for recurrence surveillance.

Conclusion

Papillary microcarcinoma is similar to larger papillary carcinomas with tumor characteristics and age-based recurrence rate that extends for many years, justifying long surveillance after surgery.

The follow-up of patients with differentiated thyroid cancer and undetectable thyroglobulin (Tg) and Tg antibodies during ablation

OBJECTIVE

This retrospective study describes the role of serum thyroglobulin (Tg) in relation to tumor characteristics in the prediction of persistent/recurrent disease in patients with differentiated thyroid cancer (DTC) with negative Tg at the time of ablation.

DESIGN

Between 1989 and 2006, 94 out of 346 (27%) patients with DTC had undetectable Tg at the time of 131I ablation and were included in this evaluation. The group of 94 patients consisted of 15 males and 79 females in the age range of 16-89 years with a median follow-up of 8 years (range 1-17). All medical records and follow-up parameters of the 94 patients were evaluated for the occurrence of persistent/recurrent disease. In patients with persistent/recurrent disease hematoxylin-eosin-stained slides of the primary tumors and/or metastatic lesions were also reviewed for histological features including immunostains for Tg.

RESULTS

During follow-up, 8 out of 94 (8.5%) patients showed persistent/recurrent disease: in the course of the disease two patients showed Tg positivity, three showed Tg antibody (TgAb) positivity, and the other three showed persistently undetectable Tg and TgAb. Patients who developed Tg and/or TgAb positivity during follow-up had a significantly shorter disease-free survival period when compared with patients with persistently undetectable Tg and TgAb (P<0.006). Histological features were not able to predict the recurrent status.

CONCLUSIONS

Follow-up of Tg and TgAb in patients with initially negative Tg and TgAb is useful since a number of patients had shown detectable Tg or TgAb during follow-up indicative for persistent/recurrent disease. Tg and TgAb negativity at the time of ablation is not a predictive determinant for future recurrent status.

Diagnostic value of serum thyroglobulin measurements in the follow-up of differentiated thyroid carcinoma, a structured meta-analysis

OBJECTIVE

To investigate to what extent thyroid remnant ablation and withdrawal from thyroxine are required to achieve sufficient accuracy of serum thyroglobulin (Tg) measurements as an indicator of tumour recurrence in the follow-up of patients with differentiated thyroid carcinoma.

DESIGN AND METHODS

We conducted a meta-analysis of the literature from 1975 to 2003 on serum Tg measurements in the follow-up of differentiated thyroid carcinoma. In a computer-based search, we initially found 915 articles that were finally narrowed down to 120. These 120 papers were subjected to strict in/and exclusion criteria, leaving 46 articles (totalling 9094 patients). Data from these articles were extracted in a structured fashion and were grouped according to initial therapy, TSH status, Tg assay method and definition of a 'gold standard'. Original 2 x 2 tables were pooled by summary receiver operating characteristic curve analysis (sROCa), best estimates of sensitivity and specificity being obtained by the combination of sROCa and Mantel-Haenszel odds ratios.

RESULTS

Despite considerable differences between series in laboratory and clinical methodology, we consistently found higher specificity for Tg measurements after thyroid remnant ablation than after surgery alone. Highest pooled sensitivity 0.961 +/- 0.013 (SE) was found for immunometric assay (IMA) after thyroid remnant ablation and thyroid hormone withdrawal, at a specificity of 0.947 +/- 0.007. Pooled sensitivity decreased significantly if ablated patients were tested while on thyroid hormone (0.778 +/- 0.023, at a specificity of 0.977 +/- 0.005). Significantly decreased pooled specificity was found in patients who did not undergo remnant ablation (sensitivity 0.972 +/- 0.023, at a specificity of 0.759 +/- 0.028). If recombinant human TSH (rhTSH) stimulation was used as a substitute for thyroxine withdrawal, sensitivity remained high (0.925 +/- 0.018) while specificity decreased to 0.880 +/- 0.013. In all analyses, specificity of Tg would decrease when unspecified activity in the thyroid region at scintigraphy was considered benign, whereas sensitivity decreased when such activity was considered malignant.

CONCLUSION

This study confirms that the best accuracy of Tg-guided follow-up in patients treated for differentiated thyroid carcinoma is obtained if treatment includes remnant ablation, and Tg testing is performed while off thyroxine.

PET in the follow-up of differentiated thyroid cancer

Fluorine-18-fluorodeoxyglucose (FDG) PET has become an increasingly important functional imaging modality in clinical oncology. This article will focus primarily on the role of FDG PET during treatment and follow-up of thyroid cancer. The major role of FDG PET is in patients with elevated thyroglobulin (Tg) levels where thyroid cancer tissue does not concentrate radioiodine rendering false-negative results on I-131 scanning. FDG PET imaging takes advantage of the increased uptake of FDG in cancer cells and is sensitive (60-94%) to the detection of recurrent or metastatic cancer in patients who have negative radioiodine scans. The specificity (25-90%) of PET imaging is relatively less than its sensitivity because some inflammatory processes avidly accumulate FDG. PET can fail to localize the tumour sites in some patients with well-differentiated thyroid cancer that retain good iodine ability. This can result the well recognized phenomenon of "flip-flop" depending on the differentiation of the thyroid cancer. Several studies have documented the higher accuracy of PET, compared with other imaging modalities in the evaluation of patients with recurrent or metastatic differentiated thyroid cancer. The value of thyroid stimulating hormone stimulation for FDG PET has recently been reported. Therefore, if available, this method should be considered in all patients of differentiated thyroid cancer with suspected recurrence and/or metastasis.

Postoperative management of differentiated thyroid cancer

The large numbers of studies on the postoperative management of differentiated thyroid carcinoma allows us to use adjuvant treatment and follow-up studies more selectively based on patient risk for recurrence and mortality. Recurrent differentiated thyroid carcinoma is more easily and more effectively treated with early diagnosis. With this in mind, patients who are at high risk for life-threatening recurrent disease should be treated aggressively and followed up expectantly. In these patients, adjuvant treatment with 131I ablation and thyroid hormone suppression is appropriate. External irradiation may be considered, especially for patients with postoperative residual disease. Close follow-up with stimulated thyroglobulin and 131I whole body scans should be performed to facilitate early detection of recurrent disease. Low-risk patients may be effectively treated with more conservative management. 131I ablation has not resulted in improved survival in these patients. Follow-up with serum thyroglobulin after initial negative 131I whole body scan may be appropriate in these patients. Management of patients at intermediate risk remains controversial. Recombinant human thyrotropin allows us to obtain stimulated serum thyroglobulin and promises the ability to perform 131I ablation and whole body scan without the need for thyroid hormone withdrawal. Functional radionuclide imaging, such as FDG PET, now allows us to localize recurrent disease in patients with elevated serum thyroglobulin but negative 131I scan.

Recombinant TSH-stimulated, radioguided differentiated thyroid carcinoma surgery

A novel approach to locating and surgically resecting occult metastatic foci in a 25-year-old female with a history of total thyroidectomy for differentiated thyroid carcinoma was attempted. Two iodine-131 (131I) body scans were performed: one after the patient underwent a 2-3 week thyroxine withdrawal, and another the following week utilizing recombinant TSH-stimulation. Then the patient was treated with 151 mCi of 131I, and 2 weeks later, without further hormonal manipulation, she had radioguided surgery. The two diagnostic 131I body scans were negative, but the post-therapy scan was positive. Two weeks later after pre-operative skin marking, radioguided surgery localized metastatic foci in the central compartment neck just dorsal to the suprasternal notch. No other foci were identified with the probe at surgery. At pathology, 2 of the 12 nodes were positive, as well as a 1 mm metastatic focus in the fat. Provocative imaging protocols, aggressive radioiodine therapy, and the novel use of radioguided surgery to attempt a cure in an 131I image-negative metastatic thyroid carcinoma patient was performed. No other cases using these combined diagnostic and therapeutic efforts have been reported in the literature.

Serum thyroglobulin measurement. Utility in clinical practice

Serum thyroglobulin measurement has greatly facilitated the clinical management of patients with differentiated thyroid cancer and a variety of other thyroid disorders. Thyroglobulin autoantibodies remain a significant obstacle to the clinical use of thyroglobulin measurement. The interpretation of any given thyroglobulin value requires the careful synthesis of all pertinent clinical and laboratory data available to the clinician. The diagnostic use of rhTSH-stimulated thyroglobulin levels has greatly facilitated the follow-up of low-risk patients with thyroid cancer. Although the measurement of thyroglobulin mRNA from peripheral blood is likely to affect the future management of these patients, it is expected that serum thyroglobulin measurement will continue to have a principal role in the care of patients with differentiated thyroid cancer.

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.

Prospective randomized clinical trial to evaluate the optimal dose of 131 I for remnant ablation in patients with differentiated thyroid carcinoma

BACKGROUND

Radioiodine has been used for more than a half-century to ablate thyroid remnants following thyroid surgery, but a single optimal dose has not been established. We designed a prospective randomized trial to determine the optimal dose of 131 I for remnant ablation.

METHODS

Using a simple randomization technique, 149 patients with remnant thyroid were incorporated into 4 treatment groups. Twenty-seven of these patients were administered 25 to 34 millicurie (mCi) of 131 I (30 +/- 1.5), 54 received 35 to 64 mCi (50.6 +/- 5.4), 38 received 65 to 119 mCi (88.6 +/- 14) and 30 patients received 120 to 200 mCi (155 +/- 28.7). Six months to 1 year after treatment, all subjects were reassessed after withdrawing L-thyroxine for 4 to 6 weeks. A successful ablation was defined as the absence of thyroid bed activity in 5 mCi 131 I neck scan at 48 hours along with 2 adjunctive criteria which were the neck uptake of <0.2% of the administered activity and the thyroglobulin (Tg) value of <10 ng/mL.

RESULTS

Applying the above criteria, we observed complete ablation of 17 of 27 thyroid gland remnants (63%) in the 30 mCi group, 42 of 54 (77.8%) in the 50 mCi group, 28 of 38 (73.7%) in the 90 mCi group and 23 of 30 (76.7%) in the 155 mCi group. When the radiation-absorbed dose was calculated, a 30 mCi dose delivered approximately 20,000 centigray (cGy), a 50 mCi dose about 30,000 cGy, a 90 mCi dose about 50,000 cGy, and a 155 mCi dose about 130,000 cGy.

CONCLUSIONS

Increasing the empirical 131 I initial dose to more than 50 mCi results in plateauing of the dose-response curve and thus, conventional high dose remnant ablation needs critical evaluation. Based on dosimetry results, one should aim to deliver about 30,000 cGy to the thyroid remnant, as higher doses do not appear to yield a higher ablation rate.

Thyroid nodules in childhood and adolescence

Thyroid nodules are uncommon in the paediatric age group. One hundred and twenty-two children and adolescents underwent thyroidectomy for nodular thyroid disease in the Endocrine Surgical Unit at the Royal North Shore Hospital over a 37 year period. In the adolescent age group (13-18 years) 99 thyroidectomies were performed and the pattern of thyroid disease was similar to that seen in adults. In the prepubertal are group (0-12 years), the major difference was the high incidence of thyroid malignancy, especially in males. Of 23 prepubertal children undergoing thyroidectomy for nodular disease, malignancy was found in 38% of boys and 13% of girls. Multicentric papillary cancer (66%) and cervical lymph node metastases (80%) were very common, despite which the long-term survival was excellent.

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.

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.

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.

Total thyroidectomy in the management of differentiated thyroid cancer: a review of 258 cases

Controversy continues to surround the management of differentiated thyroid cancer. For the past 20 years, a standardized protocol of total thyroidectomy followed by radioiodine ablation has been followed at Royal North Shore Hospital. During the period 1966-83, 327 cases of thyroid malignancy were treated surgically and, of these, 258 were differentiated thyroid cancer. Following total thyroidectomy, the incidence of recurrent nerve palsy was 2.8% and that of permanent hypoparathyroidism 3.2%. The overall 10 year cumulative survival for these patients was 87%. Whilst there were apparent differences in survival depending on the pathological type of tumour (papillary, follicular, mixed), further analysis shows that most of the differences in prognosis can be explained on the basis of age and sex alone. Young patients (less than 60 years) have an excellent 10 year survival (96%) whilst that for the elderly is only 61%. Males have a worse prognosis at 10 years than females. Total thyroidectomy is a safe procedure for the treatment of differentiated thyroid cancer. It allows the subsequent evaluation and treatment of unrecognized metastatic disease and offers the young patient a potentially normal lifespan.

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)