My dog with the cancer (hemangiosarcoma, has had it for a little over a month now and had one dose of chemo about 3 or 4 weeks ago, but was too toxic for him to do it again) has been acting kind of strangely today. He just didn't seem quite like himself. I'm really upset about it. I asked my mom (she's a medical doctor, but it may be very different for dogs) and she said that it might be caused from the cancer metastizing (spreading) to the brain. She also says that it could have been caused by the brain getting damaged from chemo. What do you guys think? Should I be worried about this? This is the first day that he has been acting differently, but he isn't too different, but I can tell something is a miss, as can my mom. What could this be?