Prospective multicenter study of thyroiscarcinoma treatment: initial analysis of staging and outcome. National Thyroid Cancer Treatment Cooperative Study Registry Group

Prognostic indicators in differentiated thyroid carcinoma

BACKGROUND

Thyroid cancer ranges from well-differentiated lesions with an excellent prognosis to anaplastic carcinoma, which is almost uniformly fatal. Thus, methods to assess the behavior of thyroid malignancies are necessary to arrive at appropriate treatment decisions.

METHODS

We discuss the factors that affect the prognosis of patients with well-differentiated thyroid malignancies, including papillary, follicular, Hürthle cell, and medullary thyroid carcinomas. We also review the presentation, therapy, and outcome of patients seen at our center over a span of 50 years. These data have identified those prognostic factors that are predictive of survival and recurrence in differentiated thyroid cancer.

RESULTS

Several classifications with different variables have been developed to define risk-group categories. Three widely used systems, in addition to the TNM staging system, include AGES, AMES, and MACIS.

CONCLUSIONS

A better understanding of independently important prognostic variables will result in improved patient care and treatment.

Recombinant thyrotropin versus thyroid hormone withdrawal in evaluating patients with thyroid carcinoma

Patients with previously treated thyroid carcinoma require lifelong monitoring for recurrent disease. Two diagnostic tests that play a central role in follow-up of these patients--radioiodine whole body scanning and serum thyroglobulin measurement--are most accurate during thyroid-stimulating hormone (TSH) stimulation. Temporary discontinuation of thyroid hormone therapy was previously the sole effective approach for TSH-stimulated testing. However, hormone withdrawal was associated with the morbidity of hypothyroidism and occasional tumor progression. The introduction of recombinant TSH (rTSH)-stimulated testing offers an alternative therapy. Recent clinical trials have shown that the sensitivity of combined rTSH-stimulated radioiodine scanning and serum thyroglobulin measurement has equivalent sensitivity to testing after thyroid hormone withdrawal. Furthermore, measurement of the rTSH-stimulated thyroglobulin concentration is a more sensitive way to detect residual thyroid cancer or normal tissue than thyroglobulin measurement on thyroid hormone therapy alone. The results of these trials are reviewed and strategies for implementing rTSH-mediated testing are presented.

Initial treatment of differentiated thyroid carcinoma

Many large, retrospective studies have been performed and form the basis for how we define risk groups of patients with differentiated thyroid carcinoma and how the three basic therapeutic modalities (surgery, radioiodine and levothyroxine) affect two primary outcomes disease recurrence and death. In this review, we have hopefully distilled much of that information into a proposed current therapeutic approach to individual patients with differentiated thyroid cancer.

Medullary thyroid carcinoma: clinical characteristics, treatment, prognostic factors, and a comparison of staging systems

BACKGROUND

The clinical courses of patients with medullary thyroid carcinoma (MTC) vary, and a number of prognostic factors have been studied, but the significance of some of these factors remains controversial.

METHODS

The study group consisted of 104 patients with MTC or C-cell hyperplasia managed at the hospitals of the University of California, San Francisco, between January 1960 and December 1998. Patients were classified as having sporadic MTC, familial non-multiple endocrine neoplasia (MEN) MTC, MEN 2A, or MEN 2B. The TNM, European Organization for Research and Treatment of Cancer (EORTC), National Thyroid Cancer Treatment Cooperative Study (NTCTCS), and Surveillance, Epidemiology, and End Results (SEER) extent-of-disease stages were determined for each patient. The predictive values of these staging or prognostic scoring systems were compared by calculating the proportion of variance explained (PVE) for each system.

RESULTS

Fifty-six percent of the patients had sporadic MTC, 22% had familial MTC, 15% had MEN 2A, and 7% had MEN 2B. The overall average age at diagnosis was 38 years, and patients with sporadic MTC presented at an older age (P < 0.05). Thirty-two percent of the patients with hereditary MTC were diagnosed by screening (genetic and/or biochemical). These patients had a lower incidence of cervical lymph node metastasis (P < 0.05) and 94.7% were cured at last follow-up (P < 0.0001) compared with patients not screened. Patients with sporadic MTC who had systemic symptoms (diarrhea, bone pain, or flushing) had widely metastatic MTC and 33.3% of those patients died within 5 years. Overall, 49.4% of the patients were cured, 12.3% had recurrent MTC, and 38.3% had persistent MTC. The mean follow-up time was 8.6 years (median, 5.0 years) with 10.7% (n=11) and 13.5% (n=14) cause specific mortality at 5 and 10 years, respectively. Patients with persistent or recurrent MTC who died of MTC lived for an average of 3.6 years (ranging from 1 month to 23.7 years). Patients who had total or subtotal thyroidectomy were less likely to have persistent or recurrent MTC (P < 0.05), and patients who had total thyroidectomy with cervical lymph node clearance required fewer reoperations for persistent or recurrent MTC (P < 0.05) than patients who underwent lesser procedures. In univariate analysis, age, gender, clinical presentation, TNM stage, sporadic/hereditary MTC, distant metastasis, and extent of thyroidectomy were significant prognostic factors. Only age and stage, however, remained independent prognostic factors in multivariate analysis. The TNM, EORTC, NTCTCS, and SEER staging systems were all accurate predictors of survival, but the EORTC prognostic scoring system had the highest PVE in this cohort.

CONCLUSIONS

Screening for MTC and early treatment (total thyroidectomy with central neck lymph node clearance) had nearly a 100% cure rate. Patients with postoperative hypercalcitoninemia without clinical or radiologic evidence of residual tumor after apparently curative surgery may enjoy long term survival but have occult MTC. Only patient age at presentation and TNM stage were independent predictors of survival. The EORTC criteria, which included the greatest number of significant prognostic factors in our cohort, had the highest predictive value.

Serum thyroglobulin levels after thyroxine withdrawal in patients with low risk papillary thyroid carcinoma

We hypothesized that elevated levels of serum thyroglobulin (Tg) are frequently found as the only index of residual neoplasm in patients with low-risk papillary thyroid carcinoma. The records of patients operated on for papillary thyroid carcinoma over a 2-year period were reviewed, and the patients were allocated to risk groups by a validated staging method that does not include Tg levels. Of the 35 patients who manifested a low-risk carcinoma, 9 (26%) exhibited elevated Tg concentrations (11-53 ng/mL) during thyroxine withdrawal after therapies, while clinical, scintigraphic, and radiographic studies at least 1 year later showed no evidence of tumor. Prior scintigraphic imaging of therapeutic doses of 131I in 8 of 9 patients demonstrated no distant metastases, further confirming the low-risk status of this group. The staging method predicts that only 0.9% of patients with low-risk papillary carcinoma will have a cause specific death in 20 years. Elevated Tg concentrations have not been shown to forecast independently the survival of patients with low-risk papillary carcinoma. Thus, although frequently encountered, elevated Tg concentrations are unlikely to predict shortened survival in patients with papillary carcinoma for whom low risk has been determined from other data.

Advances in the diagnosis and management of thyroid neoplasms

Thyroid cancers are still the most common endocrine cancers. They are dominated by well-differentiated carcinomas, including papillary carcinoma, follicular carcinoma, and medullary thyroid carcinoma. Diagnosis is based on fine-needle aspiration cytologic examination. Recently, reverse transcription polymerase chain reaction for the detection of cancer-specific mRNA was shown to be a useful adjunct in both initial diagnosis and detection of recurrent disease. In addition, positron emission tomography has become a valuable tool for staging and surveillance of thyroid cancer. Given the gradual perfection of surgical technique and reduction in complication rates, near-total and total thyroidectomy should be offered to patients with well-differentiated carcinoma. For medullary thyroid carcinoma, near-total and total thyroidectomy with routine central and bilateral functional neck dissection are recommended. So far, no effective treatment exists for anaplastic thyroid carcinoma.

Strategies for thyrotropin use to monitor patients with treated thyroid carcinoma

Detection of residual and recurrent thyroid carcinoma requires long-term monitoring of patients with serum thyroglobulin measurement and radioiodine scanning during temporary thyrotropin (TSH) stimulation. Recombinant thyrotropin (rTSH) permits these studies to be performed without the morbidity associated with withdrawal of thyroid hormone therapy. A protocol for rTSH use is proposed, beginning with measurement of serum thyroglobulin during TSH suppression. Patients at significant risk of recurrence with a low initial thyroglobulin level then have rTSH stimulation testing. Patients with positive rTSH-stimulated thyroglobulin concentrations and/or radioiodine scans can then be directed for appropriate therapy. The previously studied 2-dose rTSH protocol with imaging at 48 hours after 131I dosing requires Monday-through-Friday testing in most settings, but new regimens may be established. rTSH-stimulated testing may be less accurate in patients with thyroglobulin autoantibodies and those with residual normal thyroid tissue, and is generally unnecessary when there is other evidence of residual disease. Physicians should consider patients' pretest probability of disease in deciding whether and how often to perform rTSH-stimulated testing after primary treatment for thyroid carcinoma.

Detection of residual and recurrent thyroid cancer by radionuclide imaging

Radioiodine-131 imaging is the traditional method of detecting residual or recurrent differentiated thyroid cancer. The stimulation of such tissues to take up radioiodine may be achieved either by complete cessation of thyroid hormone, by partial thyroid hormone withdrawal, or by the administration of recombinant human thyrotropin (TSH). Complete or partial thyroid hormone withdrawal may result in serum TSH concentrations adequate for radioiodine imaging in up to 90% of patients. When known or suspected recurrent or metastatic disease is not evident on radioiodine imaging, single photon emission tomographic imaging with either thallium-201 chloride or technetium-99m-MIBI compounds may detect up to 80%-90% of cancers at least 1 to 1.5 cm in size, although specificity is less than with 131I. Fluorine-18-FDG positron emission tomography is a somewhat less available but acceptable substitute for thallium-201 or 99mTc-MIBI imaging. Tumor foci that concentrate either TI-201 or 18FDG intensely with little or no 131I uptake appear to behave more aggressively than those concentrating 131I avidly.

Toward a standard clinicopathologic staging approach for differentiated thyroid carcinoma

Physicians attempting disease staging for differentiated thyroid carcinoma have a broad variety of clinicopathologic classification approaches from which to choose. Unfortunately, no consensus has yet emerged as to the optimal method, and considerable differences of opinion still exist. Eight of the most commonly used classifications are described, along with results of recent comparative analyses of multiple schemes. Recommendations are provided to permit standardized approaches to clinicopathologic staging, and future research directions are identified.

Thyrotropin suppression and disease progression in patients with differentiated thyroid cancer: results from the National Thyroid Cancer Treatment Cooperative Registry

The ideal therapy for differentiated thyroid cancer is uncertain. Although thyroid hormone treatment is pivotal, the degree of thyrotropin (TSH) suppression that is required to prevent recurrences has not been studied in detail. We have examined the relation of TSH suppression to baseline disease characteristics and to the likelihood of disease progression in a cohort of thyroid cancer patients who have been followed in a multicenter thyroid cancer registry that was established in 1986. The present study describes 617 patients with papillary and 66 patients with follicular thyroid cancer followed annually for a median of 4.5 years (range 1-8.6 years). Cancer staging was assessed using a staging scheme developed and validated by the registry. Cancer status was defined as no residual disease; progressive disease at any follow-up time; or death from thyroid cancer. A mean TSH score was calculated for each patient by averaging all available TSH determinations, where 1 = undetectable TSH; 2 = subnormal TSH; 3 = normal TSH; and 4 = elevated TSH. Patients were also grouped by their TSH scores: group 1: mean TSH score 1.0-1.99; group 2: mean TSH score 2.0-2.99; group 3: mean TSH score 3.0-4.0. The degree of TSH suppression did not differ between papillary and follicular thyroid cancer patients. However, TSH suppression was greater in papillary cancer patients who were initially classified as being at higher risk for recurrence. This was not the case for follicular cancer patients, where TSH suppression was similar for all patients. For all stages of papillary cancer, a Cox proportional hazards model showed that disease stage, patient age, and radioiodine therapy all predicted disease progression, but TSH score category did not. However, TSH score category was an independent predictor of disease progression in high risk patients (p = 0.03), but was no longer significant when radioiodine therapy was included in the model (p = 0.09). There were too few patients with follicular cancer for multivariate analysis. These data suggest that physicians use greater degrees of TSH suppression in higher risk papillary cancer patients. Our data do not support the concept that greater degrees of TSH suppression are required to prevent disease progression in low-risk patients, but this possibility remains in high-risk patients. Additional studies with more patients and longer follow-up may provide the answer to this important question.