Med Onc consultation PRIOR to lumpectomy/mastectomy?

I honestly can't remember exactly when I first met with the MO, but I know it was after surgery.  I think before rads, but can't be sure.   For me, there was never any question that I would be having a lumpectomy (small area of DCIS with even smaller micro-invasion and much less averse to rads than to losing sensation), so it didn't really enter into it.   If you are still debating treatments, then by all means ask for a referral to someone who can answer your questions.   I actually found my rad onc to be the one who did the best job breaking things down for me, but I think that was more a personality thing than knowledge per se.

My DCIS was considered Grade 2, but did have comedo necrosis and a micro-invasion so I suspect that the 2 was an average, and there were parts that would be considered more aggressive.   The numbers I was given (which may of course be different than yours) was a 30% recurrence risk with lumpectomy alone, reduced to 15% with rads, and to about 9% with Tamoxifen.   The other risk of course is of a new primary, and that I was told was between .5-1% a year.  I was told that is cumulative but know others who have been told differently, so hard to know for sure.    

Of course my risk of getting it when I did was less than 2%, so not sure I place too much faith in numbers anymore, LOL.

That is what my BS re commended, which is why I ended up with a lumpectomy. It actually was an incisional biopsy because my DCIS was found with a stereotaxic biopsy. I lucked out because my lesion was so small I had clear margins.

In looking at the BC statistics, be sure to identify if they are talking about morbidity (getting the disease), or mortality (dying from it).

My breast center left it up to me.  I was going into BMX surgery expecting to need only tamoxifen after.  Even with this 'simple' treatment expectation, I wanted to meet my MO before surgery.  I'm glad I did:  I ended up needing her a whole lot!  In hindsight, once I got the pathology surprise and needed chemo, I felt confident with her because I'd already met her and liked her.  I didn't have to worry about any new doctor stress.

You might want to consider contacting Dr. Lagios for his perspective on your situation - many women who've come through this site have used him for a 2nd opinion and he seems more willing than most doctors to offer specifics about recurrence risk.  If you do a search of his name on this site, you find lots of threads by women who've gone to him.

A couple of other thoughts.  First, if your DCIS is close to the chest wall, this means that rads might be recommended even after a MX, if you have positive or very close margins. So going with the MX might not mean that you'll get to pass on rads, and rads can make reconstruction more challenging.  Second, if you are that concerned about the SNB and the risk of lymphedema, you might want to consider at least starting with a lumpectomy. An SNB won't need to be done, and then you'll know if your final diagnosis is pure DCIS, in which case you will have avoided unnecessary node removal.  If some invasive cancer is found, then you would at that point need to have the SNB, but that's possible after a lumpectomy, whereas it's more difficult - and virtually never attempted - after a MX.  You'll also know at that point how large the margins are, and you'll get a preliminary idea of what your post-surgical breast will look like.  With that info, you might choose to move on to a MX, or you might be satisfied with the lumpectomy. 

 If you are uncertain about what to do surgically, you can always do a MX after a lumpectomy but you can never go back to a lumpectomy after a MX.

When the cancer is pure DCIS, the criteria for rads after a MX is strictly margin size.  But that's where subjectivity comes in.  It used to be (back when I was diagnosed) that rads was virtually never suggested, no matter how close the margins.  But after a couple of small studies indicated that there may be a significantly higher recurrence risk with close margins (if I recall, one study had the rate at 16% for those with margins of 2mm or less), this started to change.  Some surgeons still don't suggest rads unless the margins are positive, but these days more and more are recommending rads after a MX for DCIS when margins are 1mm or closer.  

If you do a search on the board within the DCIS forum with the words "radiation" and "mastectomy", you'll find a number of threads where this has been discussed and where you'll find women who had pure DCIS and yet still had rads after their mastectomies.