Hi Cressida,
My situation is a bit different to your, but similar enough that I thought I would share it in case it helps.
I had triple neagtive b/c diagnosed in left breast in June 2009. Had chemo (4 EC and 4 Taxol (NOT taxotere), then a WLE and then rads. Then a year later found I had a brca1 mutation, so this year had bilateral mastecomies. A tumour was found, this time in righ breast. As the tumour was exactly the same (grade 3, triple negative with lymph involvement) no-one sure whether this is a 'new' primary or a recurrence and question about whether it was even there when I last had chemo (too complicated to explain), so had chemo again - this time taxotere and carboplatin. I had 5. Couldn't do 6.
I was told there are lots of chemos out there and you are right its is really scarey when you know that is all there is. I really suffered on chemo. I did not think I could possibly do it again this year, but I did. So if I did, you can too - if it comes to that. Another lady said you could have rads more than once. I was told this was not advisable as I had already had it to the right side of chest wall.
I spoke to a lady through breast cancer care who had a triple neagtive b/c which reoccurred only a couple of months after she finished rads. She had more chemo (same regimen as me) and a number of years on, she is fine.
Like you, I worried about long term effects of extra chemo. We discussed this alot. I know what they are but don't want to scare you. I think its fair to say I was/am as afraid of the chemo effects as the cancer.
This is all really garbled and quick as have to go and get daughter, so do ask if you want to know more. You are never alone!
Rattles xx
PS with me, it wasn't about margins etc, but the risk of spread