Molecular Types and Neoadjuvant Chemotherapy in Patients with Breast Cancer- While Molecular Shifting is More Common in Luminal a Tumors, The Pathologic Complete Response is Most Frequently Observed in Her-2 Like Tumors

Background: Pathologic complete response (pCR) is one of the most important target end-points ofneoadjuvant chemotherapy (NACT) in patients with breast cancer (BC). In present study, we aimed to investigatethe relationship between molecular subtypes and NACT in patients with BC. Materials and
Methods: Using theAkdeniz University database, 106 patients who received NACT for operable breast cancer were retrospectivelyidentified. Prognostic factors before and after NACT were assessed. According to the molecular subtypes,molecular shifting after NACT and tumoral and nodal response to NACT were analyzed.
Results: The distributionof subtypes was: Luminal A, 28.3% (n=30); Luminal B, 31.1% (n=33); HER2-like, 24.5% (n=26); and basal like/triple negative (BL/TN), 16.0% (n=17). According to molecular subtypes, pCR rates in both breast and axillarywere 0%, 21.4%, 36.4% and 27.3% for luminal A, luminal B, HER2-like and BL/TN, respectively (p=0.018).Molecular subtype shifting was mostly seen in luminal A type (28.6%) after the NACT. The pCR rate in breastand axillary was significantly higher in patients with HER2-like type BC.
Conclusions: In patients with HER-2like type BC, NACT may be offered in early stages. Additionally, due to molecular shifting, adjuvant treatmentschedule should be reviewed again, especially in the luminal A group.