Long-term survival data were collected retrospectively from 52 patients with cytokine-refractory metastatic renal cell carcinoma who received axitinib in a completed phase II study (protocol 1), 11 of whom enrolled in a continuing access protocol (protocol 2), for the current observational study (protocol 3). In a post hoc analysis, the patients were grouped into quartiles based on cycle 1 day 1, 1- to 2-hour post-dose axitinib plasma levels to explore the impact of drug exposure on efficacy.
The 5-year survival rate was 20.6 % (95 % CI, 10.9 % -32.4 % ), with a median follow-up of 5.9 years. Frequent all-grade adverse events were fatigue (n = 38; 73.1 % ), diarrhea (n = 34; 65.4 % ), hypertension (n = 33; 63.5 % ), and nausea (n = 33; 63.5 % ). Quartile 3 patients (axitinib level, 45.2-56.4 ng/mL; n = 12) had the best clinical outcome: objective response rate 82 % , median progression-free survival (PFS) 28.3 months, and median OS that was not reached after 5 years.
Axitinib was well tolerated and provided an estimated 5-year survival rate of 20.6 % for cytokine-refractory metastatic renal cell carcinoma. Exploratory analyses showed numerically higher objective response rate and longer OS and PFS in patients who achieved post-first-dose axitinib plasma concentrations within a specific range.