Mar 2, 2012 02:18PM , edited Mar 2, 2012 02:19PM by Beesie
From the mammo and MRI, how large does it appear that your area of DCIS is? That's a big factor in whether or not your surgeon will be able to deliver wide margins.
If a lumpectomy can deliver wide margins (ideally 1cm or more all around), that signficantly reduces the risk of recurrence. Personally if I had a small single focus of DCIS (maybe 1cm or less), if it was not high grade and there was no comedonecrosis, and if I came out of the lumpectomy with really good margins, I would skip radiation.
Radiation cuts recurrence risk by 50% so the benefit of radiation really depends on how much your recurrence risk is with surgery alone. With DCIS that is high grade and multi-focal, and if the margins are relatively small (2mm, 3mm), the recurrence risk can be as high as 40% or more (I've seen one study that put the recurrence risk for that type of situation as high as 60%). In that case (a 40% recurrence risk), radiation would cut the risk to 20% and Tamoxifen (for DCIS that is ER+) would cut it further to around 10%. So obviously there is a lot of benefit from those treatments. On the other hand someone who has a small single focus of lower grade DCIS and who has good margins after surgery might start off, before radiation, with a recurrence risk that is in the range of 5%. In that case, radiation could cut the risk to 2.5%; for me, that wouldn't be worth it.
As for whether it makes more sense to have a mastectomy, only you can answer that. Some women choose mastectomies in order to avoid radiation. In my case, having had a very large (more than 7 cm) area of DCIS that was multi-centric and high grade with comedonecrosis, I had no choice but to have a mastectomy. If I'd had a choice, I would have opted for a lumpectomy (with radiation if it was necessary). My reconstruction is good, but it's nothing like a natural breast.
This information about DCIS recurrence rates might be helpful:
http://www.breastdiseases.com/dcispath.htm The VNPI index
http://theoncologist.alphamedpress.org/content/3/2/94/T2.expansion Older data but still useful.
Radiation Oncology/Breast/DCIS I'm not a wiki fan but the results of a couple of studies of wide excision alone are quoted.