Thyroid Cancer - Overview
Thyroid cancer was first described at the end of the eighteenth century. For one and a half centuries surgery remained the only effective therapeutic option for this cancer, until in 1946 radioiodine therapy was performed for the first time. Radioiodine therapy was brought to Germany 4 years later, in 1950. In the intervening 50 years, the use of iodine-131 has proved able to cure the cancer and its metastases. Percutaneous radiation therapy had been added to the therapeutic armamentarium, but even now there is heated debate as to its potential.
Suppressive L-thyroxine supplement is a prerequisite for successful treatment, while cytotoxic drugs are mainly used for palliation.
During the past 10 years, various new diagnostic and therapeutic approaches have been introduced. High-dose radioiodine therapy as well as redifferentiation therapy with retinoic acid seem beneficial.
Diagnostic procedures such as magnetic resonance imaging (MRI), positron emission tomography (PET), as well as isonitriles (MIBI) and thallium (201 Tl), have proved useful for the follow-up of thyroid cancer.
Two special issues are also discussed in this book. Iodine supplementation in areas of iodine deficiency has led to a change in pathology insofar as papillary thyroid cancer (with a better prognosis) has become more frequent than follicular carcinoma. A special chapter is dedicated to thyroid cancer in Chernobyl children.
The thyroid gland is located low in the front of the neck, below the Adam’s apple. The gland is shaped like a butterfly and wraps around the windpipe or trachea. The two wings or lobes on either side of the windpipe are joined together by a bridge, called the isthmus, which crosses over the front of the windpipe.
Thyroid cancer accounts for nearly 2% of all new cancers diagnosed in the United States every year, according to the U.S. Surveillance, Epidemiology, and End Results cancer registry (SEER) predictions. Over the last 10 years, thyroid cancer has had a larger increase in incidence than any other type of cancer.
Thyroid cancer occurs in all age groups, although its incidence increases with age, especially after 30 years of age. More aggressive forms of thyroid cancer are found in older patients. Thyroid cancer occurs three times more frequently in women than in men. Thyroid cancer originates from one of two different types of thyroid cells: follicular cells or so-called parafollicular, or C cells.
Medullary thyroid cancer remains a challenge for interdisciplinary diagnosis and therapy. The fate of the patient with medullary thyroid cancer is determined by surgery. Removal of all accessible lymph nodes and their metastases is mandatory. Percutaneous radiation therapy is usually not successful. The same holds true for cytotoxic medication. Nuclear medicine now provides new imaging procedures such as those taking advantage of 111 In-octreotide and 131 I-metaiodobenzylguanidine (mIBG) as well as 99m Tc-dimercaptosuccinic acid (DMSA). mIBG and octreotide analogues may have therapeutic potential but have not yet been evaluated clinically in sufficiently large groups of patients.
Undifferentiated (anaplastic) thyroid cancer is not covered in such depth; therapy is still unsuccessful, and the 1-year survival rate is below 10%.
We strongly feel that the development of new imaging and therapeutic procedures during the past 10 years justifies the publication of a new survey. Almost 55 years have passed since the first successful radioiodine treatment of thyroid cancer, and many textbooks have appeared, but in our opinion the past 10 years have contributed enormously to the knowledge on diagnosis and treatment of this malignancy. Molecular biology will certainly enhance our knowledge further; recombinant TSH was one of the first steps. It may be speculated that molecular biology will help us to restore the sodium/iodine symporter, as is now achieved by retinoic acid. Recently published data on the existence of the sodium/iodine symporter in other malignant tissues give reason to hope that some successful therapeutic procedures in thyroid cancer can, at least in part, be transferred to other carcinomas.
While most cases of differentiated thyroid cancer have a relatively benign course, those patients whose cancer has lost the ability to accumulate radioiodine remain a therapeutic problem. We hope that this textbook may be helpful in such instances. All the above-mentioned diagnostic and therapeutic procedures contribute to the nowadays very good prognosis of the majority of patients suffering from thyroid cancer.
Bonn, Frankfurt am Main
H.-J.Biersack, F.Grünwald