My Husband Has Stage IV Colon Cancer That Has Gone

My husband has Stage IV Colon cancer that has gone to his liver. He is undergoing chemo every 2 weeks, he keeps getting high fevers and each time has to go to the ER to rule out infection. His Doctor said it was "tumor fever", I am trying to find out if this is good or bad? Does it mean the chemo is working and killing the tumor? His CEA went down.