The goal of this systematic review is to assess the effectiveness of neoadjuvant chemotherapy and Trastuzumab in achieving pathological complete response (pCR) in patients with HER2-positive breast cancer. The main questions it aims to answer are:

• What is the overall rate of pathological complete response (pCR) in HER2-positive breast cancer patients treated with neoadjuvant chemotherapy and Trastuzumab?
• Are there any variations in the definition of pCR among the included trials?

Participants in the selected clinical trials were HER2-positive breast cancer patients with non-metastatic operable, locally advanced, or inflammatory breast cancer. The main tasks participants were asked to do and the treatments they received are as follows:

• Undergo neoadjuvant chemotherapy: Participants received chemotherapy treatment before their primary surgery.
• Receive Trastuzumab: Participants were administered Trastuzumab, a targeted therapy for HER2-positive breast cancer.

Researchers would compare the group of participants receiving neoadjuvant chemotherapy and Trastuzumab to other groups, if present, to see if there are differences in the rates of pathological complete response (pCR) or other effects.

This systematic review aimed to assess the effectiveness of neoadjuvant chemotherapy and Trastuzumab in achieving pathological complete response (pCR) in patients with HER2-positive breast cancer. The researchers identified nine clinical trials that met the inclusion criteria. These trials included patients with non-metastatic operable, locally advanced, or inflammatory breast cancer, and they evaluated the pCR as the primary or secondary endpoint.

The trials utilized different chemotherapy and targeted therapy regimens, along with varying dosages of Trastuzumab. The primary outcome of interest was the pCR rate, while other survival outcomes were not analyzed. Among the 1,209 patients who received neoadjuvant chemotherapy and Trastuzumab, the overall pCR rate was found to be 42%.

The review provided detailed information about the design of the selected trials, patient characteristics, disease staging, HER2 status, administered treatment regimens, and primary/secondary endpoints. It also mentioned slight variations in the definition of pCR across the trials.

Inclusion Criteria:

• Patients with breast cancer that was found to be HER2 positive were included
• Only patients who underwent neoadjuvant therapy were included
• All cytotoxic chemotherapy regimens were considered eligible for this systematic review given that the same drugs were given at the same dose in every trial.

Exclusion Criteria:

• Patients with metastatic breast cancer were not included in the systematic review
• Results from adjuvant therapy were excluded from this study.
• Only the most recent publication (and the most informative) was included if numerous publications of the same trial were retrieved or if there was a case mix between publications.

Female patients found to have HER2+ breast cancer were included

This study only included clinical trials. The review methods were decided before the start of the review. Studies that used the pathological complete response (pCR) as their primary or secondary endpoint were considered. The proportion of patients without invasive breast and axillary cancer was the criteria used to define pCR (ypT0/is and ypN0).

Patients with breast cancer that was found to be HER2 positive were included. If the HER2 FISH test score was 2 or higher or the immunohistochemistry score for HER2 was +3, the HER2 status was interpreted as positive.

No patient data to be shared