IMO with a tumor of that size, I would think that you'd be better off going with the mastectomy and radiation to assure that you don't have a recurrence down the road.  It's an extremely difficult decision to make - and only one that you can make.  In my experience myself and with many I know, a lumpectomy was unable to provide clear margins and a mastectomy was needed.  Why not just complete it in one surgery?  But like I said, this is a decision that only you can make.

Best of luck.

Angi

in 2000 i had a lumpectomy, which was so deep it was actually a half of mastectomy, very misshapen and ugly, followed by chemo 3 months radiation 37 treatments, and 3 more months of chemo then 5 years of tamoxifen and or arimidex which i took each half the time.  then in october 2008 the scartissue where my previous surgery was was bothering me, changed some in size and became painful. my surgeon removed the scartissue and the cancer was back in the same place.  i didn't think twice i went in and had a double maastectomy 5 weeks ago i am 59 years old and this i considered a no brainer.  my surgeon had me consult with a plastic surgeon and he put in expanders at the same time.  now i am going through saline injections each week, and it is sore some and i have a full feeling in my chest, but you can do it!!!!!   i was actually very calm the day i went to surgery, and oh yea i DID WEAR MY RED LIPSTICK!!!!!!