Utility of Surgical Axillary Staging in Microinvasive Ductal Carcinoma In Situ: A National Cancer Database Analysis

Background: Surgical axillary staging (ASx) of patients with microinvasive ductal carcinoma in situ (cT1mi) is debated due to the low occurrence of nodal metastasis. This study aimed to assess the utility of surgical axillary staging for clinically node-negative (cN0) T1mi breast cancer patients. Methods: This retrospective cohort study analyzed data from the National Cancer Database (NCDB) to investigate the axillary status of patients with cT1mi breast cancer between 2012 and 2019. Patient demographics, clinical characteristics, treatment methods, and pathologic findings were collected. Results: Of 10,843 patients, 9220 (85%) underwent ASx, whereas 1623 (15%) did not. Of the 4190 patients who underwent mastectomy, 244 (6%) did not undergo ASx, whereas 3946 (94%) did, 373 (9%) of whom were pN+. Of the 9069 patients who underwent ASx and had known nodal status, 8512 (94%) were pN– and 557 (6%) were pN+. The factors independently associated with increased odds of having positive nodes were younger age (odds ratio [OR], 1.02; 95% confidence interval [CI], 1.01–1.03; p < 0.001), black race (OR, 1.51; 95% CI, 1.12–2.10; p = 0.007), lymphovascular invasion (OR, 13.72; 95% CI, 10.25–18.36; p < 0.001), and mastectomy (OR, 1.98; 95% CI, 1.57–2.51; p < 0.001). Among the pN+ patients, only 64 (1%) had ≥3 positive nodes and would require axillary lymph node dissection (ALND). Conclusion: Surgical axillary staging is commonly performed for patients with cT1mi breast cancer despite the pN– status of most and the disproportionate morbidity associated with ASx. Identifying factors that predict a higher likelihood of pN+ status could allow for personalized surgical approaches, reducing unnecessary ASx for many patients.