Background: Sunitinib (SU) is a multitargeted tyrosine kinase inhibitor with antitumor and antiangiogenetic activity. Evidence for clinical activity in HCC was reported in 2 phase II trials [Zhu et al and Faivre et al, ASCO 2007] using either a 37.5 or a 50 mg daily dose in a 4 weeks on, 2 weeks off regimen. The objective of this trial was to demonstrate antitumor activity of continuous SU treatment in patients (pts) with HCC. Methods: Key eligibility criteria included unresectable or metastatic HCC, no prior systemic anticancer treatment, measurable disease and Child-Pugh A or B liver dysfunction. Pts received 37.5 mg SU daily until progression or unacceptable toxicity. The primary endpoint was progression free survival at 12 weeks (PFS12) defined as 'success' if the patient was alive and without tumor progression assessed by 12 weeks (± 7 days) after registration. A PFS12 of ≤ 20% was considered uninteresting and promising if ≥ 40%. Using the Simon-two minimax stage design with 90% power and 5% significance the sample size was 45 pts. Secondary endpoints included safety assessments, measurement of serum cobalamin levels and tumor density. Results: From September 2007 to August 2008 45 pts, mostly male (87%), were enrolled in 10 centers. Median age was 63 years, 89% had Child-Pugh A and 47% had distant metastases. Median largest lesion diameter was 84 mm (range: 18 - 280) and 18% had prior TACE. Reasons for stopping therapy were: PD 60%, symptomatic deterioration 16%, toxicity 11%, death 2% (due to tumor), and other reasons 4%; 7% remain on therapy. PFS12 was rated as success in 15 pts (33%) (95% CI: 20%, 49%) and failure in 27 (60%); 3 were not evaluable (due to refusal). Over the whole trial period 1 CR and 40% SD as best response were achieved. Median PFS, duration of disease stabilization, TTP and OS were 2.8, 3.2, 2.8 and 9.3 months, respectively. Grade 3 and 4 adverse events were infrequent and all deaths due to the tumor. Conclusions: Continuous SU treatment with 37.5 mg/d daily is feasible and demonstrates moderate activity in pts with advanced HCC and mild to moderately impaired liver dysfunction. Under this trial design the therapy is considered promising (> 13 PFS12 successes).