A system for treating tissue includes a probe assembly having a cannula, a shaft, and one or more needle electrodes. The shaft has a distal end, a proximal end, and a lumen extending between the distal and proximal ends of the shaft, and is slidable within the lumen of the cannula. Each needle electrode has a lumen that may be placed in communication with a port at a proximal end of the probe assembly, and is configured to deliver an occlusive element to a site. The system may further include an embolization actuator for delivering the occlusive element. A method of treating tissue includes placing an electrode at a site of a treatment region, occluding at least a part of a vessel located adjacent the site by delivering an occlusion element from an electrode, and delivering ablation energy to the site while the vessel is at least partially occluded.