Anastrozole and positive breast cancer

I’m post menopausal and had triple positive breast cancer. I’m finished treatment but now have positive lymph nodes for estrogen positive based cancer cells. My onc put me on anastrozole (armidex). Anyone know if this is compatible for me or what genes this would involve? Tamoxifen is a good match for my genes according to my health report. How can I find out about anastrozole?