F45The power of traditional prognostic factor and immunohistochemical (IHC) surrogate molecular subtypes of breast cancer (BC) in predicting neoadjuvant chemotherapy response: results of a retrospective study

Background: Neoadjuvant chemotherapy (NAC) improves surgical outcomes in local advanced BC when mastectomy is technically impossible and in early cases of operable BC desiring breast conservative surgery. Many clinical trials established the prognostic significance of pathological complete response (pCR) after NAC. In this study we assessed both traditional prognostic factor (histological grade (G), ER/PR status, Ki-67 rate, HER2 overexpression) as well as the surrogate intrinsic subtypes BC reclassification regarding their power to predict neoadjuvant chemotherapy benefit. Patients and methods: We reviewed data of 58 patients with BC at Stage II and III that received in a single oncology unit NAC with Anthracyclines and Taxanes +\- Trastuzumab according HER2 overexpression between 2010 and 2015. pCR was defined as no evidence of residual invasive cancer (or very few scattered tumor cells) in primary tumor and lymph nodes. Interactions between pCR and single HIC prognostic factors (ER/PR receptors, HER2 status, Ki-67) and each surrogate molecular subtype (Luminal A-like, Luminal B-like HER2-, Luminal B-like HER2 + , HER2-enriched, Triple Negative) of BC were analyzed. Results: In our retrospective study, eighteen (31%) out the 58 patients achieved pCR. Higher rate of pCR was observed in patients with ER and PR negative BC (p = 0.01 and p = 0.005, respectively) with high ki-67 proliferation rate (p= 0.01), and HER2+ overexpressed (p = 0.01) BC tumors. The multivariate analysis indicated that HER2 overexpression was the most important predictive factor to pCR (HR 8.239 p = 0.01). As regard IHC surrogate intrinsic subtypes reclassification, Triple Negative tumors (33%), Luminal-B HER2+ (27.8%) and HER2 enriched (22%) BCs show much higher rates of pCR. Conclusions: Our findings may influence clinical practice. In fact, in patients who received NAC for locally advanced BC, traditional prognostic factors as ER, PR, Ki-67, and HER2 overexpression appeared to be also predictive biomarkers of chemotherapy efficacy. The highest rate of pCR was observed in Triple Negative tumors. Patients who received NCT combined with Trastuzumab exhibited a higher pCR rate than those who received other regimens.