Breast Cancer Presenting with Intravascular Tumor Emboli in Axillary Soft Tissue: Recurrence Risk and Radiotherapy Outcomes

Abstract

<h3>Purpose/Objective(s)</h3> Intravascular tumor emboli in axillary soft tissue (ITE) is a rare pathologic finding in breast cancer and is associated with higher axillary nodal disease burden. The independent prognostic and predictive value of this biomarker is unknown, as is the role of radiotherapy for ITE. <h3>Materials/Methods</h3> We analyzed breast cancer patients treated at our institution from 1992-2020, excluding those over 90 years of age at diagnosis, primary tumors >5cm in size, receipt of neoadjuvant chemotherapy, or those with synchronous bilateral breast cancers. A 1:3 propensity score match was performed between patients with ITE and those without. Matching was based on age, pathologic T stage, number of positive nodes removed, receipt of radiotherapy or chemotherapy, and biologic subtype. Disease free survival (DFS) was evaluated using a Cox regression analysis. Locoregional recurrence (LRR) and distant recurrence were evaluated using competing risks methods. These endpoints were compared between patients with versus without ITE. Among those with ITE, we evaluated whether radiotherapy (RT) improved outcomes using the same methods with a six-month landmark. <h3>Results</h3> We identified 127 patients with ITE, of whom, 103 (81%) were propensity score matched to 309 without ITE. Median follow up from surgery was 6.9 years (IQR 2.5, 10). 5-year DFS for those with ITE was 68% (95% CI 57%-82%) versus 78% (95% CI 73%-84%) for those without ITE (HR 1.37, 95% CI 0.82-2.30, p = 0.2). ITE was associated with increased likelihood of distant recurrence (p=0.02; 5-year cumulative incidence 26%, 95% CI 16%-38% and 14%, 95% CI 10%, 19%, respectively), but was not associated with LRR (p=0.97; 5-year cumulative incidence 5.4%, 95% CI 1.3%-14% and 8.7%, 95% CI 5.6%-12%, respectively). Among those with ITE, 5-year DFS was 74% (95% CI 63%-87%) for those receiving RT versus 32% (95% CI 10%-98%) among those not receiving RT (HR 0.33, 95% CI 0.12-0.91, p=0.03). <h3>Conclusion</h3> Patients with intravascular tumor emboli in axillary soft tissue exhibited higher rates of distant recurrence compared to a propensity score matched control group. Among patients with ITE, those who received RT demonstrated improved DFS.