Treatment of anaplastic thyroid cancer with tyrosine kinase inhibitors targeted on the tumor vasculature: initial experience in clinical practice

Anaplastic thyroid cancer (ATC) is a rarely occurring refractory disease. While recent clinical trials have demonstrated the efficacy of tyrosine kinase inhibitor (TKI) therapy for ATC, evidence is scarce in clinical practice. In this study, we reviewed our initial experiences with TKI treatment in ATC patients with the aim of revealing the efficacy and safety of the same in clinical practice. We retrospectively reviewed our experiences with TKI treatment use in ATC patients diagnosed at our institute from 2014 to 2019. Changes in the patients' neutrophil-to-lymphocyte ratio (NLR) by TKI therapy introduction as well as their clinical factors to indicate the efficacy were examined. Seven patients showed no indication for TKI treatment, while 13 (65%) received treatment. The median duration of TKI treatment was 1.9 months. All patients died, and the overall survival period from diagnosis was 4.7 (95% confidence interval: 2.0-11.5) months. Adverse events ≥Grade 3 were observed commonly (92.3%), and resulted in the termination of TKI treatment in six cases (46.1%). Existence of multiple unfavorable characteristics (higher Prognostic Index) was associated with poor survival. The NLR decreased after the introduction of TKIs and increased again when treatment failed. The response rate to TKI among the ATC patients were approximately 30% in practice. Although the duration of the response was short, several patients demonstrated long survival durations when TKI treatment was provided after successful multidisciplinary treatment to control local disease. Decreases in high NLR values during treatment may suggest the continued effect of TKIs.