Hi. Brain cancer is a very wide term. The most common in adults are metastatic brain tumor. it simply mean that tumor is originally from some other part of the body that has spread to brain. from the description provided by you it seems to be metastatic brain tumor as you mentioned of increasing spots. The principle of treatment( if it is metastatic brain tumot) is to find the original cancer and treat as per tumor site. For brain lesions Whole brain radiotherapy(WBRT) is the standard treatment. As far as time is concerened the data says median survival of 6 months in brain mets treated with whole brain radiotherapy. it means that 50 patients out of 100 patients will survive more than 6 months with WBRT. Its difficult, if not immpossible, to say in which 50% your mother will fall. Wishing her good health and early recovery