Conclusions
The present phase I clinical trial indicated that suicide gene therapy through stereotactic intratumoral injection of allogeneic ADSCs carrying HSV-TK gene followed by prodrug administration is safe in patients with recurrent GBM. Moreover, although this study is underpowered, it seems that the present novel suicide gene therapy protocol could lead to significant improvements in PFS and OS in patients with recurrent GBM. Volumetric analysis of MR images also showed significant reductions in both CET and FLAIR volumes after 12 months compared with the baseline. Changes in peripheral blood cells and cytokines also suggested an immune response, which peaked early after the prodrug administration. Although this novel cell-based suicide gene therapy was safe, future phase II/III clinical trials with adequate power are required to compare its efficacy in improving clinical outcome with control group, including patients who merely receive standard therapy.