When I was diagnosed last year with breast cancer the doctor immediatley stopped my HRT so the hot flushed came back 100 fold.
Nothing we could do at that time apart from having operation, then radiation and going from there. I found the Catapress (Clondine) helped me intensely.
I start cancer drugs in a fortnight and they apparently can have hot flushes as well as a side effect. So all good times ahead although I figure will just increase Catapress if I have a problem. FYI am already on Effexor so they do not help my hot flushes.
Good luck and take care.