LAUSR

OBJECTIVE Following neoadjuvant chemotherapy (NAC) in breast cancer (BC), complete treatment response is achieved in some patients, while treatment response is limited in others. Predicting non-responder patients can prevent exposure to adverse effects associated with chemotherapeutic agents and delays in selecting other treatment modalities. In this study, we aimed at identifying predictive factors related to tumor regression in patients with BC who received NAC. PATIENTS AND METHODS This single-center cohort included 91 patients with BC who underwent surgery following NAC based on pretreatment tumor biopsy. According to BC molecular subtype, tumor regression grade (TRG) was determined using the Miller-Payne scoring system in patients who received standard NAC. Immunohistochemical stainings for VEGFR3 and CD44 were applied to needle core biopsies obtained prior to NAC in these patients. RESULTS Pathological complete response (pCR) was achieved in 20 patients (22%). In univariate analysis, high Ki-67 expression, ER negativity, and HER2 positivity were determined to be predictive factors of TRG (p < 0.05). In multivariate analysis, Ki-67 was the single independent predictor of TRG, with a 1.05-fold effect size. CD44 and VEGFR3 levels did not affect TRG or survival (p > 0.05). There was a significant difference in TRG according to molecular subtype of BC (p < 0.001). The treatment response was 5.5-fold higher in HER2-positive patients compared with HER2-negative patients. CONCLUSIONS pCR rates were significantly higher in TNBC, HER2, and luminal HER2+ subtypes when compared with luminal HER2- subtype. Ki-67 >25% and ER negativity had a favorable effect on TRG after NAC. CD44 and VEGFR3 were not effective in predicting treatment response.