Arggh that's a tough one!
I had similar outcomes from surgery (left-side mastectomy) - sentinel node was positive but ALND came back as all clear. I wanted to throw everything we could at it now while I'm relatively
young (45) & healthy (besides the C) to reduce the chances of it
coming back later. Add to that, my cancer was detected in the lympho-vascular system on the breast so I went ahead with chemo to make sure no little microscopic bits made an escape.
Did your oncologist go through the numbers with you - rates of survival based on the specific findings in your pathology and the different combination of treatments? That can help (if your a stats/numbers kind of a person) to make that decision. It sucks as you just want someone to give you the one true answer :)
Hugs to you!