Abstract MicroAbstract The influence of body mass index (BMI) as a predictive factor for response to neoadjuvant chemotherapy, measured by pathologic complete response (pCR), was examined in 324 breast cancer (BC) patients. Mutivariable regression analysis did not reveal an association between pCR and continuous as well as categorical BMI. Additional subgroup and meta-analysis showed comparable results. Therefore BMI is not a relevant clinical factor for pCR in BC patients. Introduction There is only limited from clinical routine on the relevance of body mass index (BMI) on pathologic complete response (pCR) following neoadjuvant chemotherapy (NAC) in breast cancer (BC) patients. Patients and Methods The impact of BMI on pCR and survival outcome was examined in 324 primary non-metastatic BC patients. An additional meta-analysis was performed on the current data and relevant previously published studies in clinical routine. Results Multivariable regression analysis identified lymph vascular invasion (OR=0.05; CI: 0.01-0.18; p=0.0000), grading 3 (OR=3.12; CI: 1.59-6.12; p=0.0009) and HER2/neu-status (OR= 4.76; CI: 1.86-12.18; p=0.011) as independent factors for pCR after NAC. There was no association between pCR and continuous as well as categorical BMI . Various additional subgroup analyses of molecular BC subtype (triple-negative, luminal-like, HER2-luminal, HER2-like) and BMI also showed no association. These findings were confirmed by the meta-analysis. Except for one subgroup analysis in which overweight and obese patients were combined as one group, no association between BMI and pCR as well as survival outcome was found. Conclusions BMI was not established as a relevant clinical factor. Only lymph vascular invasion, grading 3, luminal-like and HER2/like BC subtype showed predictive and prognostic impact in BC patients receiving NAC.