Now researchers at MIT think they has found a way to test the efficacy and interactions of cancer drugs in the patient's actual tumor, thanks to a gadget the size of a grain of rice. The device, according to a study published today in Science Translational Medicine, can hold tiny doses of up to 16 different drugs; once the device is implanted into the patient's tumor (it is designed for tumors close to the surface of the skin), the doses seep out into the surrounding tumor. After about a day, the researchers remove the device and the parts of the tumor around it to see which drugs worked best to kill the cells. After a few on skin, prostate and breast cancer cells that were implanted in mice, the researchers tried the device on a particularly aggressive kind of breast cancer. The patients experienced very few side effects.