I was in exactly the same situation as you - 2.8cm lump, clear margins, one micrometastasis in the sentinel lymph node, and was offered a choice of EITHER axillary node clearance OR additional radiotherapy on the armpit OR chemo.
I chose chemo in the end because I didn’t want more surgery, but only after a lot of agonising as i had been deeply anti-chemo from the start.
In the end, my surgeon convinvced me by showing a recent study from Holland on outcomes for women in exactly the same position - early stage cancer, ‘favourable’ tumour characteristics, micrometastasis - who either did or didn’t choose to have chemo - there being no standard protocol for micromets, because it’s only fairly recently that they’ve even been able to identify them.
Anyway, after five years it showed a 10% higher rate of disease-free survival for women who did have chemo, and that convinced me. (it was, however, only one study, albeit a large one)
According to my oncologist , in my particular circumstances it translated to a 7-8% increase in my chances of staying disease-free, but that’s still significant. I’m now about to do my last chemo -FEC6 - this week, and it’s been hideous, but I’m glad I’ve done it, if only because if the cancer does come back I won’t always be wondering if the chemo would have made any difference.
There is a genetic test that can be done to see if your cancer is likely to respond to chemo, but it’s very expensive - a couple of thousand pounds. I didn’t do it because my particular tumour was of a kind the test doesn’t work very well on, so it was likely t ogive an inconclusive result.
But generally, in terms of reducing the risk of recurrence, chemo does not have a huge effect -7-8% is probably as much as you can hope for, and that means the chemo only helps 7 or 8 people out of 100 - for the rest it has no effect at all, which was somethnig that really did my head in. There is no way of knowing whether the chemo has worked unless thee cancer comes back, which means that it HASN’T worked.
Chemo is truly horrible, and takes 18 weeks out of your life - but it’s the best they’ve got to increase your survival chances. As I reach the end, I’m glad I did it, although I probably wouldn’t have said the same half way through.