Brief Summary: This pilot study will assess the safety and feasibility of using an implantable microdevice to measure local intratumor response to chemotherapy and other clinically relevant drugs in malignant brain tumors. * The device involved in this study is called a microdevice. * The drugs used in this study will only include drugs already used systemically for the treatment of gliomas.

Detailed Description: This research study is a Pilot Study, which is the first time investigators are examining this study device in brain tumors. The FDA (the U.S. Food and Drug Administration) has not approved the microdevice as a treatment for any disease. Investigators are studying the safety of the microdevice and the effects of different drugs for each specific tumor. Brain tumors are known to be very different from each other and respond differently to different drugs. It would be very helpful to find out what drugs have the best chance of working in each specific tumor. This research study involves drugs that are released by a small device, as small as the tip of a needle, that is inserted into the tumor at the time of surgery and is removed at the end of the surgery. The goal of this research study is to prove that microdevices can be used to find out which drugs have better effects on treating malignant brain tumors. Participants will be in this research study for up to 30 days. Expected enrollment is about 12 people.