Objective: We examined the therapeutic effect of adding of pertuzumab in combination with trastuzumab as neoadjuvant chemotherapy for HER2-positive breast cancer.
Participants: Overall, 27 patients with HER2-positive breast cancer who had completed neoadjuvant chemotherapy and undergone surgery between January 2014 and January 2020 were included in the study. We performed a retrospective analysis of the relationship between HER2 gene amplification and the therapeutic effect of pertuzumab in this group. For the anti-HER2 treatment, only trastuzumab was administered to all patients until December 2018, and then a combination of trastuzumab and pertuzumab was administered to 4 patients from January 2019.
Results: The case distribution based on histological therapeutic effect was: 4 patients with Grade 1, 12 patients with Grade 2, and 11 patients with Grade 3. Patients with immunohistochemistry scores of 3+ and high signal ratios of HER2/ CEP17 in FISH testing tended to have better therapeutic outcomes than other patients.
Discussion: Outcomes similar to those observed in this study were reported in other cases where pertuzumab was used for anti-HER2 treatment. We expected that the therapeutic effects of pertuzumab would be better in patients with high HER2 expression. However, further research is required to understand the effects of pertuzumab in patients with cT1c that were not included in the Neo Sphere trial. The therapeutic effects of adding pertuzumab to the treatment in patients with cT1c and lymph node-positive breast cancer were indicated by comparison with our cases.