Thyroid Factor

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In 1994, Mazzaferri and Jhiang [56] already noticed a very high recurrence rate but low mortality rate in children and adolescents with differentiated thyroid carcinoma. This was confirmed by Samaan et al. [3] in 1992 in a comparative study on 140 patients below 20 years of age and 1,459 patients of >20 years with differentiated thyroid carcinoma. In both groups the frequency of papillary carcinoma (86 vs. 80%), thyroidectomy (73 vs. 65%) and 131I therapy (48 vs. 45%) was similar, but extrathyroidal spread was more prevalent in the younger age group (74 vs. 57%). Recurrences were more frequent at age

<20 years than in the older group (37 vs. 22%), but mortality was lower (3.6 vs. 11.3%). The number of actual recurrences in the children was higher than expected (48 vs. 30, p < 0.001) but not so in the adults (301 vs. 319), and the number of actual deaths in the children was lower than expected (5 vs. 18, p < 0.001) but not so in the adults (166 vs. 153). The median follow-up in this study was 11 years, with a range of 1-43 years.

Although the above findings are reconfirmed by many other smaller series, the low mortality rate of pediatric differentiated thyroid carcinoma might to some extent reflect relatively short follow-ups compared with patients' lifespans [4]. Most reports have a median follow-up of <15 years, but cause-specific deaths may occur after longer time intervals [57]: e.g. mortality was 10% in 34 patients followed up for >20 years [6], and 15% of 40 patients diagnosed at age <12 years died after 12-33 years [2]. The relatively short follow-up also may lead to underestimation of the recurrence rate. The median time to recurrence is 7 years, but events occur up to 44 years after presentation [58, 59]. In the historical series of the Royal Marsden Hospital the median overall survival was 53 years; presentation with distant metastases predicted poorer survival, and recurrences had also a higher risk of death with a median survival of 30 years [58]. A 100% survival at 10 years' follow-up seems to be the rule rather than the exception. Disease-free survival at 5 and 10 years follow-up is 80 and 61%, respectively [40]. The majority of children with lung metastases achieve complete remission, and even partial responders rarely progress [2, 36, 40]. Over a 20-year follow-up, few if any cause-specific deaths were noted in pedi-atric patients with lung metastases, in contrast to the 10-year mortality rate of 30-60% in adults with lung metastases [4, 59].

The risk of developing recurrent disease is increased by lymph node metastases at presentation, less than total thyroidectomy, and no radioiodine ablation as observed in many studies (table 1). In the recent multivariate regression analysis by Jarzab et al. [4] presented in table 1, age is not an independent risk factor in this respect. In contrast, age is a major determinant of recurrence risk in many other reports [19, 40, 43, 45, 58]: e.g. 20-year recurrence-free interval was 10% in patients aged <10 years and 48% in patients aged 10-18 years at diagnosis [60]. Among 137 cases of papillary thyroid carcinomas <21 years of age with a median follow-up of 6.6 years, univariate analysis demonstrated recurrence to be more common in patients with multifocal disease (OR 7.5) or large tumors >2 cm (OR 4.1), and in those with palpable cervical lymph-adenopathy (OR 3.0) or distant metastases at diagnosis (OR 2.8); by multivari-ate analysis the only significant predictor of recurrence was multifocality, which was also true for the 38 patients with follicular carcinoma (OR 22) [61].

Most of the outcome studies described so far, refer to patient series collected in the distant past. The outcome of patients who were diagnosed more

Table 2. Differentiated thyroid carcinoma in children and adolescents: clinical presentation, initial treatment and long-term outcome in studies reported after 2000 [18, 62-67]

Clinical presentation

Median age 16 years

73% females, 27% males

89% papillary, 11% follicular carcinomas

26% extrathyroidal invasion

53% lymph node metastases

16% lung metastases

Initial treatment (n = 308)

80% (near) total thyroidectomy

64% 131I ablation

Long-term outcome (n = 281)

Median follow-up 65 months

22% recurrences

0.3% mortality

16.4% residual disease

83.3% disease-free recently might be different in view of the recommendations to perform (near) total thyroidectomy and radioiodine ablation postoperatively. This was evaluated by summarizing seven studies on children and adolescents with differentiated thyroid carcinoma published after 2000 (table 2) [18, 62-67]. Sex distribution and histology type are in agreement with previous series. At clinical presentation, the cancer was already widespread as evident from a high frequency of extrathyroidal invasion, lymph node and distant metastases, again confirming more advanced disease in children with differentiated thyroid carcinoma than in adults. Remarkably in comparison with past figures is the higher frequency of near-total, total or completion thyroidectomy (80%) and of direct postoperative 131I therapy for thyroid ablation and metastases (64%). The outcome after a median follow-up is reassuring: only one child died and 83% had become disease-free. It can be concluded that the prognosis of children and adolescents with differentiated thyroid carcinoma is in general rather good.

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