ERBB2 and neoplasm: Treatment was generally well tolerated, with grade ≥3 haematological toxicity being the most frequent one, without differences between the two groups.<h4>Conclusions</h4> This prospective real-world study suggests a trend toward lower pCR in HER2-low compared with HER2-zero tumours, although not statistically significant. The lower use of immunotherapy among HER2-low patients may have influenced these results and should be considered when interpreting comparative efficacy.