Radiotherapy?

After a DCIS diagnosis I had surgery a few weeks ago. My consultant is now recommending Radiotherapy but I find the idea of it really daunting. I’m also worried if I have it and then the DCIS returns there will be no other option than to have a mastectomy as I’ve been told you can only have Radiotheeapy once. 

if anyone can give any info and/or advice I’d be really grateful.