I had very low numbers in a grade 3, stage 3 er+ breast cancer (no lymph involvement), what are the chances of metastasis elsewhere?

Not enough informati: Stage iii is divided into stage iiia, iiib and iiic. Your chance of remaining without metastatic disease for ten years varies from 90% to 40% depending on which stage you are. To give you a more helpful answer, i need to know: what your t stage is. What your n stage is. What your ki67 is. What your her2 status is. Any information you can get to me will add to my ability to help.

Not sure what..: ...You mean by "low numbers". If you truly had a stage 3, node negative cancer, it would be a t4n0m0 (stage iiib). Being er+ is good but a grade 3, stage 3 still has a fair risk of relapse. You need an aggressive approach with chemo, surgery, radiation, and endocrine therapy. My advise: do your best to complete therapy and do not focus too much in numbers or odds. Best 2u.