ER -ve DCIS have had Tamoxifen offered

I had a single mastectomy, established tumour, one malignant lymph node,  HER2 positive, and took Letrozole (way past menopause) for ten years. So far (eleven years) so good! I don’t know of anything that will categorically protect you from a recurrence or another unrelated cancer. But I felt like I wanted to do whatever was recommended (five years initially, ten years following research of effectiveness) to avoid going through BC again. For the record, while I had some side effects (one was possibly age related), I had none of the common ones - no joint pain, aches, menopausal symptoms, etc. Remember you can always stop a treatment if the side effects are too difficult. Best wishes whatever you choose.