The effect of surveillance for differentiated thyroid carcinoma in childhood cancer survivors on survival rates: a decision-tree-based analysis.

Background: Childhood cancer survivors (CCS) who received radiation therapy exposing the thyroid gland are at increased risk of developing differentiated thyroid cancer (DTC). Therefore, the International Guideline Harmonization Group (IGHG) on late effects of childhood cancer therefore recommends surveillance. It is unclear whether surveillance reduces mortality. Aim: The aim of this study was to compare four strategies for DTC surveillance in CCS with the aim of reducing mortality: Strategy-1, no surveillance; Strategy-2, ultrasound alone; Strategy-3, ultrasound followed by fine-needle biopsy (FNB); Strategy-4, palpation followed by ultrasound and FNB. Materials and methods: A decision tree was formulated with 10-year thyroid cancer-specific survival as the endpoint, based on data extracted from literature. Results: It was calculated that 12.6% of CCS will develop DTC. Using Strategy-1, all CCS with DTC would erroneously not be operated upon, but no CCS would have unnecessary surgery. With Strategy-2, all CCS with and 55.6% of CCS without DTC would be operated. Using Strategy-3, 11.1% of CCS with DTC would be correctly operated upon, 11.2% without DTC would be operated upon and 1.5% with DTC would not be operated upon. With Strategy-4, these percentages would be 6.8, 3.9 and 5.8%, respectively. Median 10-year survival rates would be equal across strategies (0.997). Conclusion: Different surveillance strategies for DTC in CCS all result in the same high DTC survival. Therefore, the indication for surveillance may lie in a reduction of surgery-related morbidity rather than DTC-related mortality. In accordance with the IGHG guidelines, the precise strategy should be decided upon in a process of shared decision-making.