48 Background: Trial data show that omission of surgical axillary staging does not affect overall survival in women >70 with cT1N0 hormone receptor-positive (HR+) breast cancer, and the Society of Surgical Oncology’s Choosing Wisely recommendations advise against routine use of sentinel lymph node biopsy (SLNB) in patients with early-stage HR+ cancers. Despite this, almost 80% of women eligible for omission still undergo SLNB. We sought to explore oncologists’ perspectives of omission of SLNB in this patient population. Methods: We conducted an exploratory qualitative study using semi-structured telephone interviews with surgical, medical, and radiation breast oncologists throughout North America from 3/2020 to 1/2021. Purposive snowball sampling ensured a range of practice types. Interviews were transcribed and a team trained in qualitative analysis undertook thematic analysis guided by grounded theory to identify emergent themes. Results: Participants included sixteen surgical, six medical, and seven radiation oncologists (55% female) (Table). Overall, while oncologists in all fields expressed acceptance regarding SLNB omission in certain women >70 with cT1N0 HR+ disease, many viewed it as a complex choice based on patient comorbidities, chronologic age, patient preferences, and disease factors. Although patients’ physiologic age and life expectancy were also important decisional factors, almost all participants assessed these subjectively despite knowing that validated tools existed. Most surgeons perceived the data backing the Choosing Wisely recommendation as weak, although knowledge of specific supporting studies was low. While all participants agreed that SLNB omission does not affect survival, several radiation oncologists expressed anxiety about resultant increased regional recurrence risk. In the absence of known nodal status, medical and radiation oncologists stated they were more likely to order additional imaging, rely on OncotypeDX scores to make systemic therapy decisions, add high tangents, and be reluctant to offer partial breast irradiation. Conclusions: While surgeons are aware of the Choosing Wisely recommendation, high SLNB rates in patients eligible for omission may be driven by perceptions of the quality of the supporting data and differing ideas regarding appropriate candidacy for omission. There are downstream effects of SLNB omission on medical and radiation oncology treatment decision making and surgeons should engage in multidisciplinary discussion prior to surgery.[Table: see text]