Effect of BRAF and TERT Promoter Mutations on Thyroglobulin Response in Patients With Distant-Metastatic Differentiated Thyroid Cancer

To assess the impact of serine/threonine-protein kinase B-Raf (BRAF) V600E and telomerase reverse transcriptase (TERT) promoter mutations in patients with distant-metastatic differentiated thyroid cancer (DM-DTC) based on thyroglobulin (Tg) response to radioactive iodine (RAI) therapy.The BRAFV600E and TERT mutations in primary tumors or metastatic lymph nodes of 114 patients with DM-DTC were retrospectively examined. RAI avidity was evaluated using a posttreatment iodine-131 whole-body scan. The Tg response was dynamically assessed at a median follow-up period of 56.50 months (interquartile range, 28.43-97.98 months).BRAFV600E was detected in 38.6% of cases, the TERT mutation in 21.1% of cases, and both the BRAFV600E and TERT mutations in 14.9% of cases. Patients with both the mutations tended to be older at diagnosis (P < .001) and less multifocal (P = .011) and have more aggressive histologic subtypes (P = .011) and a higher Ki-67 index (P = .003). Patients with neither mutation tended to be have more RAI avidity than those with either the BRAFV600E mutation alone or both the mutations (P = .001 and .001, respectively). Patients with both the mutations exhibited a more unfavorable Tg response than those without both the mutations and those with the BRAFV600E mutation alone (P = .001 and .013, respectively). The Tg progression-free survival was shorter in patients with the TERT mutation alone than in those with neither mutation (P = .021), and it tended to be shorter when it coexisted with the BRAFV600E mutation (P < .001); however, no significant difference was observed between those with the BRAFV600E mutation alone and those with neither mutation (P = .890).The coexistence of the BRAFV600E and TERT promoter mutations synergistically induce the loss of RAI avidity and leads to an undesirable Tg response in patients with DM-DTC. The TERT promoter mutation appears to affect Tg response more than the BRAFV600E mutation.