Outcomes After Multimodality Therapy in Modern Breast Cancer Patients Presenting With Clinical N3c Supraclavicular Node Involvement.

Purpose/Objective(s) Breast cancer patients with clinical N3c (cN3c) disease at diagnosis have poor outcomes relative to other breast cancer patients. Radiotherapy (RT) has an important role in the management of these patients as the supraclavicular (SCV) nodes are not routinely surgically dissected. However, outcomes and prognostic factors in the era of modern neoadjuvant chemotherapy (NAC) are not well-described. Materials/Methods We reviewed breast cancer patients with non-metastatic cN3c disease treated at our institution from 2014-2019 with curative intent NAC, surgery, and adjuvant RT. All patients received nodal RT including the SCV, infraclavicular, and internal mammary nodes. Institutional guidelines recommend a 10 Gy boost to clinically resolved N3 nodal basins and 16 Gy to unresolved N3 nodes. Variables including initial and boost dose, pathologic response, and type of nodal dissection were collected. Local (LC) and regional control (RC), freedom from distant metastases (FFDM), and overall survival (OS) were analyzed with the Kaplan Meier method. A saturated multivariable Cox proportional hazards model of OS with backward elimination identified clinical variables associated with OS at P Results A total of 176 consecutive patients were analyzed. The median follow-up time was 2.83 years. The median age was 54 years, 76 (43%) were ER+/HER2-, 20 (11%) ER+/HER2+, 26 (15%) ER-/HER2+, and 54 (31%) ER-/HER2-. 102 (57%) had T3/4 disease, 41 (23%) underwent lumpectomy, 142 (81%) had pathologic confirmation of N3c, and 10 (6%) had a neck dissection. The median initial radiation dose was 50 Gy (range, 44-56.25), SCV boost 10 Gy (range, 6-16), and 156 (89%) received cumulative SCV dose ≥60 Gy. The 3-year OS, FFDM, RC, and LC were 79%, 64%, 93%, and 96%, respectively. For cumulative SCV dose of ≥60 Gy vs. Conclusion In a large, modern cohort of non-metastatic cN3c breast cancer patients treated with multimodality therapy, cumulative SCV dose ≥60 Gy was found to be associated with improved OS. Although optimal radiation dosing cannot be established from this data, a SCV radiation boost should be considered in cN3c patients treated with curative intent respecting normal tissue constraints.