Endocrine Abstracts

Introduction: Differentiated thyroid cancer (DTC) represent 85- 90 % of all thyroid cancer cases. Most of these have an excellent prognosis with standard treatment. However, between 7 and 23% will develop distant metastases and, of these, more than 65% will become radioactive iodine-refractory. In some of these patients who are considered to be radioiodine-refractory with rapidly progressive or symptomatic disease, or in patients who are not candidates for other therapies, the use of systemic therapies, such as Tyrosine kinase inhibitors (TKIs), should be considered since they have demonstrated an extension of progression-free survival.

Materials and Methods: Retrospective observational study. Data of 23 patients diagnosed with DTC who received treatment with TKIs between June 2010 and October 2019 were analyzed. Clinical response according to RECIST criteria of response to treatment, toxicities and tolerability of these therapies were evaluated at 3, 6, 12 and 18 months.

Results: There were 23 patients (11 men and 12 women). The overall mean age at diagnosis was 59,17 ± 14,59 years. 12 patients had a diagnosis of papillar thyroid cancer, 4 of follicular thyroid cancer and 7 of Hurthle cell cancer, being 70% of them stage IV. The mean time from cancer diagnosis to initiation TKIs therapy was 7.6 ± 8.7 years. Regarding the therapy: 19 were treated with Sorafenib, 3 with Lenvatinb and just 1 with Axitinib. Twelve months after the beginning of the treatment 19 patients were still undergoing TKI therapy: 12 (52.5%) had a stable disease (SD), 1 (4.3%) partial response (PR) and 6 (26.1%) progressive disease (PD). The remaining 4 patients had to withdraw: 1 due to toxicity and 3 due to death as a result of progression of the disease. A group of 15 patients completed 18 months of treatment (6 of them required a shift to second-line treatment with Lenvatinib or Axitinib) 10 had SD, 3 PR and 2 PD. A total of 7 patients (30.4%) died during this time. Adverse events occurred in 100% of the patients, being hand-foot syndrome, diarrhea and fatigue the most frequent. However, they were generally low grade (grade 1 or 2) requiring dose reductions or temporary withdrawals. There was only one definitive withdrawal due to toxicity (with Axitinb)

Conclusions: • Eighteen months after the beginning of the treatment 56.5% of the patients remained without disease progression thanks to treatment with TKIs. Despite their frequent side effects, TKIs are generally well tolerated