Memory loss

Less than one minute read time.
Mum is 88 and was diagnosed in Feb 12 with lung cancer. She can't have treatment due to COPD and heart problems. She has become very confused, can't remember words or their meaning and now has difficulty expressing herself she just can't get her words out. She gets confused about the time can't read the clock etc Has the worse happened and the cancer is has spread to her brain ? Has anyone else any experience of this? Tanks
Anonymous