72P - Real-world data on the efficacy of T-DM1 biosimilar for the treatment of HER2-positive metastatic breast cancer patients: Outcomes from a single center retrospective study in India

Background

Ado-trastuzumab emtansine (T-DM1) became the first FDA approved antibody-drug conjugate in breast cancer. This real-world study aimed to evaluate the efficacy and safety of first approved T-DM1 biosimilar (ZRC-3256) in India for HER2-positive breast cancer in routine practice.

Methods

It was a retrospective, single-center, observational study and included patients treated between May 2021 to December 2022. Eligible patients were all female with HER2-positive metastatic breast cancer treated with trastuzumab and taxane prior and at progression treated with standard dose T-DM1 biosimilar. Brain metastasis patients treated with appropriate local therapy were allowed. The primary endpoint includes response rate and progression-free survival (PFS). The secondary endpoints were time to treatment failure (TTF), safety and overall survival (OS). Descriptive statistics were used to recapitulate the patient and other related characteristics. The study was approved by the institute ethics committee.

Results

30 patients treated with T-DM1 biosimilar were included. 5 among them had brain involvement. Median age was 57 years, all had received prior HER2-targeted therapy (100%) and majority of patients (86.67%) were post-menopausal. 83.3% patients received T-DM1 therapy in 2^nd line and the complete response rate was 66.63%. Median progression free survival and time to treatment failure were found to be around 13.5 months (95% CI: 13.46 – 17.17) and 13 months (95% CI: 11.47 – 14.53) respectively. Median overall survival data is yet to mature and stand at 24 months (95% CI: 21.03 – 26.97) with limited events. Common adverse events were elevated transaminases, anemia, and thrombocytopenia, with most being manageable and reversible. 10% patients experienced adverse events of Grade 3 or above.

Conclusions

The study findings suggested that T-DM1 is effective in managing HER2-positive metastatic breast cancer and the outcomes with T-DM1 biosimilar usage in the real world are consistent with the published evidence of randomized controlled clinical trials with T-DM1. So, this biosimilar can be a reasonable option in routine clinical practice in India.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The author.

Funding

Has not received any funding.

Disclosure

The author has declared no conflicts of interest.