It is an invasive cancer, meaning it is invading healthy breast tissue, but it has not spread outside the breast. This stage also has two categories, 1A and 1B, based on whether there is any evidence of small clusters of breast cancer cells in nearby lymph nodes.
Surgery is the main treatment for stage I breast cancer. These cancers can be treated with either breast-conserving surgery (BCS; sometimes called lumpectomy or partial mastectomy) or mastectomy. The nearby lymph nodes will also need to be checked, either with a sentinel lymph node biopsy (SLNB) or an axillary lymph node dissection (ALND).
In some cases, breast reconstruction can be done at the same time as the surgery to remove the cancer. But if you will need radiation therapy after surgery, it is better to wait to get reconstruction until after the radiation is complete.
Radiation therapy is usually given after surgery to lower the chance of the cancer coming back in the breast and to also help people live longer.
Chemotherapy: If the tumor is larger than 1 cm (about 1/2 inch) across, adjuvant chemotherapy (chemo) is sometimes recommended. For women who have a hormone receptor-positive (ER-positive or PR-positive) breast cancer, most doctors will recommend hormone therapy (tamoxifen or an aromatase inhibitor, or one followed by the other) as an adjuvant (additional) treatment, no matter how small the tumor is.