Asking for prayers

My wife's sister has been battling cancer for a while, and had seemed to be doing ok as far as signs of the cancer recently, except for the lingering affects of the treatments had made her real weak.  She had to quit work a while back due to that.  Now as of today she had to have another scan because the one last weak was inconclusive. We are worried that something has come back.  She was told a while back that if it came back it would be aggressive.  We would appreciate prayers.