Abstract 46P
Background
Anti-HER2 monoclonal antibodies improved the pathologic complete response (pCR) and prognostic of human epidermal growth factor receptor 2-positive (HER2+) breast cancer (BC). Antibiotics (ATB) and proton pump inhibitors (PPI) may affect the efficacy of cancer therapies, by modulating gut microbiota and consequently disturb the immune response. Here we aimed to evaluate the impact of ATB and PPI in HER2+ BC neoadjuvant treatment response.
Methods
We conducted a retrospective observational study in HER2+ BC patients, treated in our centre with neoadjuvant chemotherapy plus trastuzumab and pertuzumab, between July 2016 and March 2022. Achieving a pCR was compared regarding the use of ATB during the first 30 days, as well as the baseline use or initiation of PPI, in the first 30 days of the neoadjuvant scheme. We excluded: cancers of unknown primary site treated as BC; uncompleted neoadjuvant scheme; absence of pathologic assessment after treatment; additional treatments performed.
Results
Fifty-four female patients were included with a mean age of 52.9 years. Twenty-nine (53.7%) had BC staged as T2 and 30 (55.6%) had positive lymph nodes. Concerning pathological features: 75.0% had a Ki-67 score >30% and 72.2% had positive hormone receptors (HR+). A pCR was obtained in 29 (53.7%) patients and, of all sample, 6 (11.1%) took ATB and 27 (50.0%) PPI. All prescribed ATB were beta-lactams and the main motive was central venous catheter infection (n=2; 33.0%). Nor ATB (8.0 vs. 13.8%; p=0.675) neither PPI intake (56.0 vs. 44.8%; p=0.413) impacted the rates of pCR obtained. Furthermore, the association of ATB and PPI also did not affect the achievement of a pCR (4.0 vs. 10.3%; p=0.615). There was a tendency for non-achieving a pCR for HR+ BC (84.0 vs. 62.1%; p=0.073), while age, tumor size, lymph nodes status and Ki-67 did not correlate.
Conclusions
In our sample ATB and/or PPI intake was not associated with lower rates of pCR obtained after neoadjuvant HER2+ BC treatment. Future studies with long-term prognostic assessment are still needed.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
A. Teixeira: Financial Interests, Personal, Invited Speaker: Novartis. All other authors have declared no conflicts of interest.