Is outcome of differentiated thyroid carcinoma influenced by tumor stage at diagnosis?

Background: There is no international consensus on surveillance strategies for differentiated thyroid carcinoma (DTC) after radiotherapy for childhood cancer. Ultrasonography could allow for early detection of DTC, however, its value is yet unclear since the prognosis of DTC is excellent. We addressed the evidence for the question: 'is outcome of DTC influenced by tumor stage at diagnosis?'. Methods: A multidisciplinary working group answered the sub-questions: 'is recurrence or mortality influenced by DTC stage at diagnosis? Does detection of DTC at an early stage contribute to a decline in adverse events of treatment?' The literature was systematically reviewed, and conclusions were drawn based on the level of evidence (A: high, B: moderate to low, C: very low). Results: In children, level C evidence was found that detection of DTC at an early stage is associated with lower recurrence and mortality rates. No evidence was found that it influences morbidity rates. In adults, clear evidence was found that less advanced staged DTC is a favorable prognostic factor for recurrence (level B) and mortality (level A). Additionally, it was found that more extensive surgery increases the risk to develop transient hypoparathyroidism (level A) and that higher doses of radioiodine increases the risk to develop second primary malignancies (level B). Conclusion: Identification of DTC at an early stage is beneficial for children (very low level evidence) and adults (moderate to high level evidence), even considering that the overall outcome is excellent. These results are an important cornerstone for the development of guidelines for childhood cancer survivors at risk for DTC.

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