These cancers are still relatively small and have not spread to the lymph nodes or elsewhere.
Local therapy: Stage I cancers can be treated with either breast-conserving surgery (lumpectomy, partial mastectomy) or modified radical mastectomy. The lymph nodes will also need to be evaluated, with a sentinel lymph node biopsy or an axillary lymph node dissection. Breast reconstruction can be done either at the same time as surgery or later.
Radiation therapy is usually given after breast-conserving surgery. Women who may consider breast-conserving surgery without radiation therapy typically have all of the following:they are age 70 years or olderthey have a tumor 2 cm or less across that has been completely removedthey have a tumor that contains hormone receptors and hormone therapy is givennone of the lymph nodes that were removed contained cancer
Although some women who do not meet these criteria may be tempted to avoid radiation, studies have shown that not getting radiation increases the chances of the cancer coming back.
Adjuvant systemic therapy: Most doctors will discuss the pros and cons of adjuvant hormone therapy (either tamoxifen or an aromatase inhibitor) with all women who have a hormone receptor–positive (estrogen or progesterone) breast cancer, no matter how small the tumor. Women with tumors larger than 0.5 cm (about 1/4 inch) across may be more likely to benefit from it.
If the tumor is smaller than 1 cm (about 1/2 inch) across, adjuvant chemotherapy is not usually offered. Some doctors may suggest it if a cancer smaller than 1 cm has any unfavorable features (such as being high-grade, estrogen receptor–negative, HER2-positive, or having a high score on one of the gene panels). Adjuvant chemotherapy is usually recommended for larger tumors.For HER2-positive cancers larger than 1 cm across, adjuvant trastuzumab (Herceptin) is usually recommended as well.