After the tumor surgery, exact treatment for each participant in this study will depend on how much of the tumor is removed during surgery and the way the tumor tissue looks under a microscope. Some participants will not require additional treatment because most or all of the tumor has been taken out. Those participants will still be on study, but they will only have observation and not receive additional treatment. Those that require additional treatment will be randomly assigned (as in the toss of a coin) to one of 2 treatment groups with an equal chance of being assigned to either group.