The Treatment of Well-Differentiated Thyroid Carcinoma

Abstract

Background: Recent decades have seen a rise in the incidence of well-differentiated (mainly papillary) thyroid carcinoma around the world. In Germany, the age-adjusted incidence of well-differentiated thyroid carcinoma in 2010 was 3.5 per 100 000 men and 8.7 per 100 000 women per year.

Methods: This review is based on randomized, controlled trials and multicenter trials on the treatment of well-differentiated thyroid carcinoma that were retrieved by a selective literature search, as well as on three updated guidelines issued in the past two years.

Results: The recommended extent of surgical resection depends on whether the tumor is classified as low-risk or high-risk, so that papillary microcarcinomas, which carry a highly favorable prognosis, will not be overtreated. More than 90% of localized, well-differentiated thyroid carcinomas can be cured with a combination of surgery and radioactive iodine therapy. Radioactive iodine therapy is also effective in the treatment of well-differentiated thyroid carcinomas with distant metastases, yielding a 10-year survival rate of 90%, as long as there is good iodine uptake and the tumor goes into remission after treatment; otherwise, the 10-year survival rate is only 10%. In the past two years, better treatment options have become available for radioactive-iodine-resistant thyroid carcinoma. Phase 3 studies of two different tyrosine kinase inhibitors have shown that either one can markedly prolong progression-free survival, but not overall survival. Their more common clinically significant side effects are hand-foot syndrome, hypertension, diarrhea, proteinuria, and weight loss.

Conclusion: Slow tumor growth, good resectability, and susceptibility to radioactive iodine therapy lend a favorable prognosis to most cases of well-differentiated thyroid carcinoma. The treatment should be risk-adjusted and interdisciplinary, in accordance with the current treatment guidelines. Even metastatic thyroid carcinoma has a favorable prognosis as long as there is good iodine uptake. The newly available medical treatment options for radioactive-iodine-resistant disease need to be further studied.

Figure

Three illustrative cases of patients with metastatic thyroid carcinoma. a) Follicular thyroid carcinoma with very good radioactive iodine uptake (left). One year after radioactive iodine therapy, CT reveals only slight evidence of possible residual tumor at the site of the original pulmonary metastases (arrows). b) Follicular thyroid carcinoma with metastases to bone, lungs, and mediastinum. Scintigraphy after radioactive iodine therapy reveals marked radioactive iodine uptake in all of the metastases. A large, osteolytic metastasis to the pelvis (arrow) was additionally treated with external beam radiotherapy, because, despite marked uptake of radioactive iodine, this form of treatment alone die not yield a sufficient radiation dose. c) Poorly differentiated thyroid carcinoma. The whole-body radioactive iodine diagnostic study (left) reveals a mediastinal lymph-node metastasis with marked uptake (thick arrow), but without any correlate in the FDG-PET (right). In contrast, the supraclavicular lymph nodes take up large amounts of FDG, but hardly any radioactive iodine (thin arrows). Standard imaging studies in thyroid carcinoma include ultrasonography of the neck and radioactive iodine scintigraphy (once or twice), and, in some advanced cases, tomographic imaging and FDG-PET. CT, computerized tomography; FDG, fluorodeoxyglucose; FDG-PET, fluorodeoxyglucose positron emission tomography.