Locoregional Management of the Axilla in Mastectomy Patients with One or Two Positive Sentinel Nodes: The Role of Intraoperative Pathology

Introduction: Controversy exists regarding optimal management of the axilla in clinically node-negative (cN0) mastectomy patients with one or two positive sentinel lymph nodes (+SLNs). We evaluated the influence of frozen-section pathology on axillary management and recurrence. Patients and Methods: We studied cN0 breast cancer patients treated from 2008 to 2018 with mastectomy and SLN surgery with one or two +SLNs. Patients with one or two +SLNs identified on frozen-section intraoperatively (FS+SLN) were compared to those with one or two +SLNs not detected by frozen section (FS–SLN). Recurrence rates were estimated using the Kaplan–Meier method. Results: Of 2295 cN0 mastectomy patients, 338 patients had one or two +SLNs: 108 (32%) FS–SLN and 230 (68%) FS+SLN. In the FS+SLN cases, completion axillary lymph node dissection (cALND) was more frequent (97% vs. 39%; P <.001), and median SLN metastasis size (5 vs. 1.3 mm; P <.001) and likelihood of positive non-SLNs (31% vs. 14%; P =.02) were greater compared with FS–SLN cases. Across all 338 patients, 40% had SLN surgery alone, and 47% of cALND patients received post-mastectomy radiation therapy (PMRT). At a median follow-up of 61 months, no axillary recurrences were observed among FS–SLN patients. Among FS+SLN patients, 97% proceeded to cALND but 49% avoided PMRT; three regional nodal recurrences were observed (all in patients treated with cALND, of whom two received PMRT). Conclusion: Mastectomy patients with one or two FS+SLNs have a higher nodal disease burden than FS–SLN patients. The majority of FS+SLN patients underwent cALND, and 51% received PMRT with very low 5-year regional nodal recurrence rates. A substantial proportion of FS–SLN patients successfully avoided both cALND and PMRT. Frozen-section pathology analysis can guide de-escalation of axillary management.