Abstract 150P
Background
Trastuzumab biosimilar were first tested and introduced in the metastatic setting. There use in the neoadjuant setting is based on equivalence on pathological complete response rate (pCR), which remain the preferable surrograte factor in Her2-positive tumors. Two biosimilars are available at ower institution since 2017 (Hertraz® 440mg Mylan and CanMab ® AbdiBrahim). The aim of this study is to compre efficacy of trastuzumab biosimilar compared to Referent Trastuzumab based on pCR.
Methods
A retrospctive study was conducted based on 193 files of stage I-III her2-positive breast cancer treated with neoadjuvant chemotherapy (NACT) including trastuzumab only, since pertuzumab is not available at our level. Baseline characteristics between the two groups were compared. A first analyse of relatio between the use trastuzumab and pCR rate was done, then a multivariate analysis added to this parameter significant predictive factors (TNM stage, molecular sub-groupe, ER/PR levels, Ki67, histology).
Results
A total of 99 patients includes in the Referent group and 94 in the biosimilars group. Baseline characteristics are summarized in the table.
Table: 150P
| Referent trastuzumab | Biosimilars | |
| Median age (min-max) | 48.1 | 52.4 |
| Premenopusal (%) | 59.6 | 55.3 |
| T: T1-2-3-4 (%) | 6.1-44.4-22.3-28.3 | 3.2-28.7-31.9-36.2 |
| N: 0-1-2-3 (%) | 36.4-53.5-10.6-0 | 35.1-47.9-6.4-10.6 |
| Stage: I-IIA-IIB-IIIA-IIIB-IIIC (%) | 6.1-25.2-24.2-20.2-24.2-0 | 1.1-19.1-25.5-15.9-27.6-10.6 |
| Histology: IDC-ILC-Other (%) | 83.8-14.1-2 | 89.4-7.4-3.2 |
| ER (median) | 30.5% | 42.5% |
| PR (median) | 20.6% | 30.1% |
| Ki67 (median) | 37.4% | 37.3% |
| Molecular group (Luminal) | 52.5% | 71.3% |
We noticed a statistically significant difference between luminal rate in the two arms (p=0.021) pCR rate in biosimilar arm was 41.5% vs 37.8% in the Referent groupe (p=0.331). In multivariate analysis none of the cited parameters was considered as a predictive factor of pCR.
Conclusions
Our study demonstrated the efficacy of trastuzumab biosomilar compared to Referent trastuzumab in the neoadjuvant setting, since the two arms whowed comparable pCR rates, even if more luminal tumors were recorded in the biosimilar arm, considered as resistance factor to neoadjuvant treatment. This is an important result considering different cost of the two options.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.