A group-sequential design will be used with the chance of remaining alive and free of progression at 6 months, called "response", as primary endpoint. The null hypothesis of a response rate ≤ 10% will be tested based on the binomial distribution of the response endpoint at a nominal significance level of 0.10 (one-sided). If the observed response rate in the 15 patients is < 20%, the null hypothesis will be accepted and study failure will be concluded. If the observed response rate is ≥ 20% (i.e., at least three out of the 15 patients show a response after 6 months), then consideration would be given to studying further. If the observed response rate amounts to at least 5 out of the initial 15 patients, the null hypothesis will be rejected and the study may be stopped after the first stage. Secondary end-points: PFS and MST will be estimated using the Kaplan-Meier method.