Low RUFY3 expression level is associated with lymph node metastasis in older women with invasive breast cancer

Purpose: Sentinel lymph node biopsy is omitted in older women (≥ 70 years old) with clinical lymph node (LN)-negative hormone receptor-positive breast cancer as it does not influence adjuvant treatment decision-making. However, older women are heterogeneous in frailty while the chance of recurrence increase with improving longevity. Therefore, a biomarker that identifies LN metastasis may facilitate treatment decision-making. RUFY3 is associated with cancer progression. We evaluated RUFY3 expression level as a biomarker for LN-positive breast cancer in older women. Methods: Clinical and transcriptomic data of breast cancer patients were obtained from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC, n = 1903) and The Cancer Genome Atlas (TCGA, n = 1046) Pan-cancer study cohorts. Results: A total of 510 (METABRIC) and 211 (TCGA) older women were identified. LN-positive breast cancer, which represented 51.4% (METABRIC) and 48.4% (TCGA), demonstrated worse disease-free, disease-specific, and overall survival. RUFY3 levels were significantly lower in LN-positive tumors regardless of age. The area under the curve for the receiver operator characteristic (AUC-ROC) curves showed RUFY3-predicted LN metastasis. Low RUFY3 enriched oxidative phosphorylation, DNA repair, MYC targets, unfolded protein response, and mtorc1 signaling gene sets, was associated with T helper type 1 cell infiltration, and with intratumor heterogeneity and fraction altered. Low RUFY3 expression was associated with LN-positive breast cancer and with worse disease-specific survival among older women. Conclusion: Older women with breast cancers who had low expression level of RUFY3 were more frequently diagnosed with LN-positive tumors, which translated into worse prognosis.