Dear Feathertop,

What a really difficult situation to find yourself in. I have to be honest and say this is out of the range of advice I can give you on this website.
However, it seems that your doctor has put in place a treatment plan and is optimistic that it will be successful. So let's hope that that is the case.
It is important to let your doctor know how important it is for you to breastfeed. I know from our point of view it sounds crazy, but breastfeeding is not important to everyone. Sometimes there is more than one treatment option, but a dr will advise ceasing breastfeeding, because they just don't realise how important it is. Before you contemplate ceasing breastfeeding I would at least seek a second opinion. It is extremely rare that breastfeeding has to stop for a medical condition to be successfully treated.
I will see if I can get any more information for you
Warm Regards
Barb