Thyroid cancer follicular

Thyroid cancer Exogenous thyroid hormone may produce regression of metastases from follicular and papillary carcinoma of the thyroid and is used as ancillary therapy of these conditions with radioactive iodine. Larger doses than those used for replacement therapy are required. 

In the treatment of well-differentiated (papillary and follicular) thyroid cancer, levothyroxine is used as an adjunct to surgery and radioiodine therapy. Generally, TSH is suppressed to less than 0.1 milliunits/L, and this usually requires a levothyroxine dose of greater than 2 mcg/kg/day. However, in patients with high-risk tumors, the target level for TSH suppression may be less than 0.01 milliunits/L. 

Tg is primarily used as a tumor marker in patients carrying a diagnosis of differentiated thyroid carcinoma (DTC). Although serum Tg is elevated in patients with thyroid cancer, including thyroid follicular and papillary carcinoma, elevations are also are seen in nonneoplastic conditions such as thyroid adenoma, subacute thyroiditis, Hashimoto s thyroiditis, and Graves disease. Serum Tg concentrations are not increased in patients with medullary thyroid carcinoma. 

Histone deacetylase inhibitors, depsipeptide (FR901228), trichostatin A (TSA), and valproic acid, increase NIS expression in thyroid cancer cell lines (Kitazono et al., 2001 Kogai et al., 2006). Depsipeptide significantly induces NIS mRNA and iodide uptake in follicular thyroid cancer cell lines (FTC 133 and FTC 236) and two anaplastic cancer cell lines (SW-1736 and KAT-4) at a low concentration (Ing/ml) in vitro (Kitazono et al., 2001). Pharmacokinetics of depsipeptide in patients have indicated that levels of more than 500ng/ml are... 

E. Follicular and anaplastic thyroid cancer E. Papillary thyroid cancer ... 

Pathological criteria for classifying thyroid cancer may show discrepancies in the differentiation between foUicu-lar adenoma and minimally invasive follicular carcinoma, and between follicular neoplasia and the folficular variant of papillary carcinoma (Lloyd et al., 2004 Saxen et ai, 1978). The inclusion of papillary microcarcinomas (1.0 cm or less in diameter), which are usually incidental findings or detected by the use of ultrasound-guided thyroid fine-needle aspiration cytology (Lin et al., 1997), the existence of radioactive fallout, which may lead to an increase of differentiated thyroid carcinoma and a rise in population age with time, should also be taken into account when analyzing the epidemiology of thyroid cancer. 

Note-. PC, papillary carcinoma FC, follicular carcinoma UC, undifferentiated carcinoma MC, medullary carcinomas TL, thyroid lymphoma NA, not applicable (TL none in males and before salt iodination, MC two and three cases before and after prophylaxis, respectively). Thyroid cancer by type, mean age and gender before (1958-1972) (I) and after (1985-2003) (II) salt iodization in the province of Salta, Argentina. 

The beneficial effects of iodine supplementation in the prevention and control of developed thyroid abnormalities due to iodine deficiency have been discussed so far in this chapter. However, supplementation with excess iodine, including the improvement of a previous iodine-deficient state, may cause thyroid dysfunctions, viz., iodine-induced hypothyroidism/iodide goiter in susceptible subjects (Roti and Vagenakis, 2000) and iodine-induced hyperthyroidism (IIH) especially in individuals over 40 years of age and who have been iodine deficient for a long period in the past (Vidor et ai, 1973). It may also increase the ratio of papillary/follicular carcinomas (Slowinska-Klencka et ai, 2002). In other words, both low and excess intake of iodine is related to further risk of thyroid disease. Although a daily intake of up to 1000 pg/day by a normal adult individual is quite safe (WHO, 1994), the upper limit is much lower in a population that has been exposed to iodine deficiency in the past. Therefore, to prevent IDD, the recommended iodine requirement in an adult individual is fixed within a narrow range of 150 rg/day (Knudsen et ai, 2000). Iodine supplementation under certain conditions in certain populations causes adverse effects, e.g., iodide goiter and iodine-induced hypothyroidism, IIH, iodine-induced thyroiditis and thyroid cancer. 

In contrast to the overall incidence of thyroid cancer, the types of cancer change if an area goes from an IDA to an ISA. In ISAs anaplastic thyroid cancer is rare and the main type of DTC is papillary thyroid cancer. The ratio between papillary and follicular thyroid cancer ranges from 6.5 to... 

Table 84.3 Changes of the ratio of papillary to follicular thyroid cancer in Austria from 1952 to 1995 due to salt iodization...

Hofstatter (1980) could demonstrate that the ratio of papillary to follicular thyroid cancer changed from 0.2 to 1.1 before and after the first introduction of salt iodization in 1963. We investigated the influence of the elevation in salt iodization to 20 mg Kl/kg salt on the histological types of DTC. Gomez-Segovia et al. (2004) found that, in the period from 1985 to 1989, the ratio was 2.6 and increased to 4.0 between 1990 and 1995. 

Increase in iodine supply changes the histological type of thyroid cancer sufficient iodine supply leads to an increase of papillary thyroid cancer, a thyroid cancer type with a better prognosis. Follicular thyroid cancer, dedifferentiated follicular thyroid cancer, and anaplastic cancer have become less frequent in Austria. 

Thyroid cancer is the commonest endocrine malignancy, with approximately 1000 new cases per year in the UK. Papillary and follicular thyroid cancer are referred to as differentiated thyroid cancer, and carry a favorable prognosis, with overall 10 year survival in the order of 90%. For most patients treatment for differentiated thyroid cancer consists... 

Figure 102.1 Percentages of different histological subtypes of thyroid oancer at diagnosis and overall 10-year survival figures. Well-differentiated (papillary and follicular) thyroid cancers are the most common histological subtypes. Anaplastic tumors are uncommon but have a significantly worse survival rate.

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