A brain scan can frequently give us a good idea as to the nature of the growth, i.e. whether benign or cancerous. Sometimes we can be almost be 100% sure. Considering the present condition of your father, his age, his weakness, his difficulty in speaking and understanding and his incontinence, the picture does fit into a cancerous condition. Sometimes, it is kinder and more dignified for the patient to be allowed to proceed to his next life. If your father was mine, I would let him be and just treat symptomatically, (eg. pain killers for pain).