Transient partial response to sorafenib treatment in an adolescent patient with MEN2B syndrome and end-stage medullary thyroid carcinoma

Medullary thyroid carcinoma in children: current state of the art and future perspectives

Medullary thyroid carcinoma (MTC) is a distinct type of malignant thyroid tumor in cell origin, biological behavior, and natural history. It accounts for 1.6% of all thyroid cancers and presents either sporadically or as a hereditary disease, the latter occurring as a part of multiple endocrine neoplasia (MEN) 2A and MEN2B syndromes or as a familial MTC disease with no other manifestations. The gene responsible for the hereditary form is the rearranged during transfection (RET) gene, a proto-oncogene located to human chromosome 10. Most pediatric MTC cases have been discovered after genetic testing investigations, leading to the concept of prophylactic surgery in presymptomatic patients. Therefore, the genetic status of the child, along with serum calcitonin levels and ultrasonographic findings, determine the appropriate age for prophylactic surgical intervention. Nevertheless, a diagnosis at an early stage of MTC warrants total thyroidectomy and central lymph node dissection with the addition of lateral/contralateral lymph node dissection depending on the tumor size, ultrasonographic evidence of neck disease, or calcitonin levels. Conversely, locally advanced/unresectable or metastatic MTC is primarily treated with multikinase inhibitors, while more specific RET inhibitors are being tested in clinical trials with promising results.

Medical management of metastatic medullary thyroid cancer

Medullary thyroid cancer (MTC) is an aggressive form of thyroid cancer that occurs in both heritable and sporadic forms. Discovery that mutations in the rearranged during transfection (RET) proto-oncogene predispose to familial cases of this disease has allowed for presymptomatic identification of gene carriers and prophylactic surgery to improve the prognosis of these patients. A significant number of patients with the sporadic type of MTC and even those with familial disease still present with lymph node or distant metastases, making surgical cure difficult. Over the past several decades, many different types of therapy for metastatic disease have been attempted with limited success. Improved understanding of the molecular defects and pathways involved in both familial and sporadic MTC has resulted in new hope for these patients with the development of drugs targeting the specific alterations responsible. This new era of targeted therapy with kinase inhibitors represents a significant step forward from previous trials of chemotherapy, radiotherapy, and hormone therapy. Although much progress has been made, additional agents and strategies are needed to achieve durable, long-term responses in patients with metastatic MTC. This article reviews the history and results of medical management for metastatic MTC from the early 1970s up until the present day.

Targeted therapy in thyroid cancer

PURPOSE OF REVIEW

Recent advances in the understanding of the biological basis for thyroid cancer have identified molecular changes in thyroid cancer cells. These changes form the basis for targeted therapies, which have been investigated with some success in patients with advanced, inoperable thyroid cancers and are the subject of this review.

RECENT FINDINGS

For patients with advanced differentiated thyroid cancers, sorafenib, selumetinib, pazopanib and sunitinib have been investigated with promising results. In the setting of advanced medullary thyroid cancer, vandetanib now has FDA approval, whereas sorafenib, sunitinib and cabozantinib have shown activity in early studies. For patients with anaplastic thyroid cancer, no targeted therapy has been proven to be effective in vivo, although preclinical work on various kinase inhibitors has shown promise. Despite the potential for disease response, significant cardiac, gastrointestinal and skin-related side effects are reported for all therapies, limiting their application outside the setting of incurable disease.

SUMMARY

Inoperable thyroid cancer still has a poor prognosis, however, the introduction of targeted therapies offers the hope of longer quality of meaningful life for this small group of patients.