From what I have read, but I may be wrong on this, there are three types of potential recurrences: local, which can be either a recurrence from stray BC cells from the original tumor, or a new primary in the same (ipsilateral) or other (contralateral) breast; regional, such as in lymph nodes or chest wall; or distant meaning metastatic stage 4 BC that may have been from dormant or circulating BC cells. For ER/PR+ HR- BC with lumpectomy there is a tool to determine risk for ipsilateral recurrence with or without hormone, radiation, and chemotherapy treatment: https://www.tuftsmedicalcenter.org/ibtr/ The Oncotype score, and the PREDICT test, provide an estimate only for the risk of a metastatic recurrence. It is my understanding that radiation may be more effective for ipsilateral risk than anti-estrogen drugs, but that AI's or tamoxifen are more effective against new primaries and more distant recurrences by decreasing the estrogen environment favored by ER+ breast cancer. Thank you @callalloo for your research on the OncotypeDX scores!