The trastuzumab biosimilar CT-P6 combined with pertuzumab and chemotherapy achieved pathological complete response rates in routine practice similar to those of the reference trastuzumab in neoadjuvant treatment of early HER2-positive breast cancer.
What was known
Trastuzumab biosimilars are biological equivalents of the original drug that broaden access to effective treatments at a lower cost. However, data on their neoadjuvant use — before surgery — in combination with pertuzumab were limited, and there was less information on possible immune responses to the biosimilar.
What this work adds
This is a prospective, multicenter, observational study in 102 patients with early HER2-positive breast cancer. Patients received the neoadjuvant regimens preferred at each hospital, with or without anthracyclines. The primary endpoint was pathological complete response, defined as the absence of invasive tumor in both the breast and axillary lymph nodes (ypT0/ypTis and ypN0). Translational markers such as soluble HER2 and anti-CT-P6 antibodies were also analyzed.
Main results
Among patients who underwent surgery, 57.43% achieved pathological complete response, with no significant differences between regimens with and without anthracyclines. Soluble HER2 and anti-CT-P6 antibodies were not significantly associated with complete response. Treatment was well tolerated: the most relevant grade 3-4 adverse events were diarrhea (2.25%) and asthenia (0.50%). No immunogenicity or clinically relevant cardiotoxicity was observed.
What it means
The authors conclude that CT-P6 with pertuzumab and chemotherapy can be used in neoadjuvant treatment of early HER2-positive breast cancer, with complete response rates comparable to reference trastuzumab and no evidence of immunogenicity. For patients and breast units, this supports confidence in biosimilars as a valid and sustainable option within curative regimens, while maintaining the expected efficacy.
Reading from the breast unit
For a breast unit, this kind of observational study provides real-world evidence on biosimilars, which sustain access to anti-HER2 treatments at a lower cost. It reinforces confidence in their use within curative regimens without expecting efficacy differences.
Reference: Alonso-Romero JL, Martínez-García J, Carrillo-Vicente R, Aramburo AF, Díez AF, Henarejos PS, et al. Translational and real-world evidence of trastuzumab biosimilar CT-P6 plus pertuzumab in neoadjuvant HER2-positive early breast cancer. Breast Cancer Research and Treatment, 2026. DOI
