Contralateral Axillary Metastasis in Patients with Inflammatory Breast Cancer.

BACKGROUND: Nearly one-third of patients with inflammatory breast cancer (IBC) present with de novo stage IV disease. There are limited data on frequency and clinical outcomes of contralateral axillary metastasis (CAM) in IBC with no consensus diagnostic and treatment guidelines. PATIENTS AND METHODS: Frequency of synchronous CAM was calculated in unilateral IBC patients at a single center (10/2004-6/2019). Clinicopathologic variables, diagnostic evaluation, treatment received, and overall survival (OS) were assessed and compared. RESULTS: Of 588 unilateral IBC patients, 49 (8.3%) had synchronous CAM. Of these, 32 (65.3%) also presented with metastatic disease at another distant site. CAM was not associated with age, tumor laterality, breast cancer subtype, grade, or cN stage (p > 0.05). The sensitivity/specificity to detect CAM was as follows: mammography (18.2%/99.2%), ultrasound (92.3%/95.5%), PET (90.1/99.1%), and MRI (76.0%/98.6%). Following systemic therapy, 22 patients had contralateral axillary surgery, and 18 received adjuvant contralateral nodal radiation. On multivariable analysis including tumor receptor subtypes, patients with stage IV-isolated CAM has statistically similar survival to stage III patients (HR 1.37, 95% CI 0.70-2.69, p = 0.36). Patients with Stage IV non-CAM (HR 2.18, 95% CI 1.66-2.85, p < 0.001) and stage IV-CAM plus other distant metastasis (HR 2.57, 95% CI 1.59-4.16, p < 0.001) had higher risk of death (reference: stage III disease). CONCLUSIONS: CAM in IBC was diagnosed in 8.3% of patients at presentation and was best identified by ultrasound and PET. We recommend routine contralateral axillary ultrasound as part of staging for all IBC patients. Diagnosis of CAM is a key first step toward much-needed prospective clinical trials evaluating management and outcomes of CAM in IBC.