Jean Rounds will have her fourth round of chemo on Thursday.
Her husband, Senator Mike Rounds, says the family is heading back to the Mayo Clinic this week. He says the family is waiting on blood test results and a recommendation from Mayo, but he says it sounds positive.
Rounds says the tumor was originally the size of a fist, but is now smaller than a golf ball.
In June, Jean was diagnosed with an aggressive high-grade tumor near her sciatic nerve.