Endocrine Abstracts

Response to therapy re-stratification approach has been recently included in the 2015 ATA guidelines as a risk-adapted approach to management of thyroid cancer. Our aim was to investigate the clinical utility of response to therapy variables obtained during early follow-up in combination with BRAF, a prominent oncogene in thyroid cancer with prognostic value. This was a retrospective multicenter study of 871 patients at 11 centers in Spain with papillary thyroid cancer followed after total thyroidectomy and radioactive iodine remnant ablation. 685 patients were re-stratified during the first year of follow-up based on response to therapy: excellent (73% of the patients), indeterminate (8%), biochemical incomplete (6%) and structural incomplete (13%). Clinical outcomes were obtained in each group and no evidence of disease (NED) was seen in 95%, 47%, 32% and 24% respectively for a median follow-up of 57 months. BRAF mutation prevalence was 51% and was significantly associated with patients who had no excellent response (31.4% vs 22.9%; HR 1.53 (95% CI, 1.080 a 2.188)). This association remained significant with biochemical incomplete response but not with structural incomplete response. Moreover, BRAF positive tumors were less likely to have distant metastasis compared with BRAF negative tumors. Patients with excellent response and BRAF negative tumors, almost 100% had NED at the end of follow-up. Patients with indeterminate and biochemical incomplete response and BRAF positive tumors, were less likely to have NED compared with BRAF negative, although the difference was not significant due to the small number of patients in each group. Our data show that indeterminate and biochemical incomplete response may not have such favourable clinical outcome as previously shown. In addition, BRAF status informs about the way papillary carcinomas disseminate (locoregional vs distant metastasis) and may help to better assess risk estimates that change over time based on response to therapy.