Is my Mom going to die from cancer?

My mom was diagnosed with a very progressive stage 3 cancer in 2004 and again 1 & 1/2 yrs later in the second . She had a mesectomy both times and did chemo and radiation the first time but when the 2nd diagnosis came chemo made her too sick to continue and she quit all treatments. Now it's 2008 and she has random problems like rashes and l bleeding even though she is past menopause. Now she has abnormal ekg's and she currently is sick with bronchitis and says her lungs hurt when she breathes. I am scared that she is going to get some other kind of cancer and p away. I get very depressed when she gets sick because I always think the worse case senerio. Can someone please tell me how cancer patients actually die or what they die from?