Cancer progress?

My mother has been diagnosed with ovarian cancer. Her cancer has spread to her stomach. So will the chemo treatments work or will they not. I guess what i am trying to understand is if all metastic cancers do recur later sometime or do they just go away completely as well? Her CA levels are normal even when she was diagnosed with cancer. And what will the doctor use to see how her cancer treatment is progressing? I mean since CA 125 is not very reliable in her case what will they use?

Thanks