SNB and mastectomy

inna,

I'll tell you the answer I got when I was in the same position as you. I was having an SNB at the same time as my mastectomy, and I was having immediate reconstruction (implant though, not DIEP). Since I'd had a microinvasion, I worried about a change in the treatment plan (radiation and/or chemo) if more IDC was found, or if my nodes were positive. The answer I got from both my surgeon and PS was that the immediate reconstruction decision was being made based on the odds. The odds were over 90% that my nodes would be clean and that no significant amount of IDC would be found during my mastectomy. If I was unfortunate and my results came out against the odds, then "we will deal with the implications of that when it happens". That seems reasonable to me (but of course didn't stop me from worrying until I got that final pathology report!).

In your case, I don't think an earlier SNB would necessarily help. If you are node positive, that probably would mean chemo, but it wouldn't necessarily mean radiation. Radiation would likely only be required if more IDC is found and it's too close to the margins. And you won't know that until after your mastectomy. So, like me, I think you have to make your decision based on the odds. Fortunately the odds are very much in your favor.

inna,

What you've been told sounds a bit odd to me.

Radiation is local; chemo is systemic.

Radiation is used to kill any cancer cells that might remain in the area of the breast. This is why it's the standard of treatment after most lumpectomies, and why it's also used after mastectomies when there are close margins.

Chemo is used when there is a risk that cancer cells might have escaped beyond the breast either through the lymphatic system or the vasular system. This risk is greatest when there is lymph node involvement or for larger tumors (hence the general rule that chemo is given for tumors that are >1cm).

What that means is that radiation may be required any time there are close margins, regardless of the size of the tumor, regardless of whether the lymph nodes are positive or negative, and regardless of whether you have a lumpectomy or mastectomy. However for women who have mastectomies, if the margins are close only for DCIS, often radiation is not prescribed because DCIS exists only in milk ducts, and even though a small amount of breast tissue remains after a mastectomy, it's unlikely that any milk ducts will be left. But if there is a close margin on IDC after a mastectomy, then radiation will be required. I know that some women go into a mastectomy thinking they are safe from requiring radiation, only to be surprised when they get their pathology report and find that they had close margins.

In your case, there are two scenerios that might lead you to require radiation. First is if you have positive nodes. In this case, radiation may be prescribed as a way to kill off any cancer cells that might be left in the nodes. Second is if you have any IDC that is close to the margin of either your chest wall or your skin. This could be the case even with just another very small microinvasion, if it's in the wrong place.

As for chemo, chemo would be required if a larger area of IDC were found - much more than the microinvasion that's was found in your lumpectomy - or if you have positive lymph nodes.

What it all means is that a negative SNB does not guarantee that you won't require radiation. Does that make sense? This whole thing probably sounds really gloomy. The important thing to remember is that that odds of you requiring either radiation or chemo are very small, which is why you aren't taking a very big risk by having your SNB together with your mastectomy, and having your DIEP and mastectomy done together.

inna,

I did understand that you only had DCIS near your margins, but since you had a microinvasion, there is no certainty that another one won't be found. You didn't have clean margins on the DCIS, which means that you don't know how far out the DCIS extends. You also don't know if there might be another microinvasion hiding in there somewhere - after all, you didn't know that the first one was in there. My DCIS extended a lot further than anyone would have thought based on what was seen on the diagnostic mammogram. Fortunately there were no more microinvasions, but there could have been. While my surgeon said that radiation was highly unlikely (and my pathology was very similar to yours), his concern was less that I would have lymph node invasion but more that I would have another microinvasion that happened to sit right on the chest wall. That's what would trigger a need for radiation.

On the other hand, it could be that your DCIS ended right at the margin. You didn't have clean margins, but maybe there is no further DCIS beyond what was already removed. Then you're competely safe. And that's the more likely scenerio.

I am scheduled for bil mastectomies on Nov 8 with SNB and possible axillary disection. DIagnosis from a stereotactic biopsy show   high grade DCIS  (comedonecrosis and cribiform ) no invasion.   MRI shows 8cm of involvement.  My surgeon indicated there might be some micro invasion.  I am planning to have reconstruction with expanders placed one to two weeks after the mastectomies.  Does anyone know what the treatment is should they find lymph node involvement?