Intermittent dosing of axitinib combined with chemotherapy is supported by (18)FLT-PET in gastrointestinal tumours

BACKGROUND: We evaluated week-on/week-off axitinib dosing plus chemotherapy in patients with gastrointestinal tumours, including tumour thymidine uptake by fluorine-18 3′-deoxy-3′-fluorothymidine positron emission tomography ((18)FLT-PET). METHODS: During a lead-in period, patients received twice daily (b.i.d.) axitinib 7 mg (n=3) or 10 mg (n=18) for 7 days followed by a 7-day dosing interruption; serial (18)FLT-PET scans were performed before day 1 and on days 7, 10, and 14. Axitinib plus FOLFIRI or FOLFOX was then administered in 2-week cycles; axitinib was interrupted on day 10 of each cycle for 7 days. RESULTS: The maximum tolerated dose of axitinib was 10 mg b.i.d., in a week-on/week-off schedule, combined with FOLFIRI or FOLFOX. Common all-causality grade 3 adverse events were neutropenia (38%), hypertension (33%), and fatigue (29%). Of 21 patients, 2 (10%) had a partial response and 12 (57%) had stable disease. Following 7 days of continuous axitinib dosing, tumour (18)FLT uptake decreased –49% from baseline and recovered to –28% and –17% from baseline, respectively, after 3 and 7 days of axitinib interruption. CONCLUSION: Axitinib administered in a week-on/week-off schedule combined with FOLFIRI or FOLFOX is supported by (18)FLT-PET data and was well tolerated in patients with gastrointestinal tumours.