Mastectomy or Lumpectomy? Sad and anxious

So sorry to have to welcome you to the club no one wants to join.   If the cancer is only on one side, I'm not sure why you would need a bilateral mastectomy (did you test positive for BRCA?), but I doubt you have to jump right to that.   Perhaps a lumpectomy could be tried, followed by a mastectomy if they can't get clean margins.   6 cm is  a large area of DCIS, but if your breasts are indeed very large, I have known of people in that situation who were able to successfully do a lumpectomy.  You would almost certainly need radiation though, which can be somewhat debilitating so might cancel out the effect of a shorter surgical recovery.    Also, would it be possible to only do the cancer side?  That way you would still have use of the other arm at least while you recover.    My mother, who was 75 at the time had a single mastectomy without reconstruction and had a fairly quick recovery.     I had a friend with Stage III cancer (so much more advanced than yours is likely to be) who had a single mastectomy followed by chemo and radiation with a DIEP reconstruction.  The DIEP was done a full year later, allowing her plenty of time to recover from the prior surgery and treatment.    My point is just that yes, the cancer needs to be removed quickly but reconstruction and even the prophylactic removal of the healthy side can wait until you are prepared to deal with it.

Also, yes, with a large area of DCIS with comedo necrosis, there is a higher probability of an invasive component, but that usually takes the form of a micro-invasion (what I had, although my area of DCIS was much smaller).    Micro-invasions almost never require chemo, so I wouldn't worry too much about that possibility unless and until you get there .... the odds are very much in your favor that it won't be an issue.