Axitinib Trough Concentration and its Influence on the Efficacy and Toxicity of Second-line Renal Cell Carcinoma Treatment.

INTRODUCTION

There are known correlations between axitinib exposure and treatment response. The aim of the article was to study relationships between the axitinib steady-state trough concentration and the treatment efficacy and toxicity.

PATIENTS AND

METHODS

35 patients (24 men and 11 women), treated or initiating treatment with axitinib, were included in the study over the period 2016-2019. Blood samples were collected following 2 weeks of treatment (in patients who initiated the therapy) and at the end of Cycles 1, 2, and 3 thereafter (in the entire study population). For concentration measurements, high-performance liquid chromatography - mass spectrometry (HPLC-MS) was applied. Treatment efficacy was assessed according to the RECIST 1.1 criteria. Therapy toxicity was evaluated according to the CTCAE criteria.

RESULTS

A statistically significant relationship between the first measured axitinib trough concentration (Ctrough first) value and treatment response (P = .004) as well as the median progression-free survival (mPFS) (P = .003) was observed. The association between axitinib Ctrough first and the median overall survival (mOS) was not statistically significant (P = .142). A statistically significant relationship was observed between the mean trough concentration from 3-month observation (Ctrough 1-3m) and treatment response (P = .008) as well as mPFS (P = .001), without a significant relationship for mOS (P = .097). At least grade 3 adverse reactions were meaningfully associated with Ctrough first (P = .012) and Ctrough 1-3m (P = .003).

CONCLUSION

There are significant relationships between axitinib Ctrough and treatment response, PFS, and grade ≥ 3 toxicity. The data collected may be used to determine indications for axitinib therapy monitoring based on Ctrough measurements.