My hubby also has bone mets and is terminal. He also suffers from confusion. I spoke with the doctor because I, like you, was worried there may be a brain tumour. She assured me that if it was a brain tumour there would be many more symptoms other than confusion. She said the confusion is caused from the meds, as well as the disease itself. He is on medication now which is helping with the confusion a little. Best advice I can give you is talk to your doctor and express your concerns.
Regards,
Princess Maggie