(153) Incidence and Timing of Ado-Trastuzumab Emtansine Infusion Reactions

Poster Abstract: Background/Rationale
Ado-trastuzumab emtansine (T-DM1) is an antibody drug conjugate approved for the treatment of metastatic HER2-positive breast cancer and the adjuvant treatment of patients with HER2-positive early breast cancer who have residual invasive disease after neoadjuvant taxane and trastuzumab-based treatment. Monoclonal antibodies as a class carry the risk for non-hypersensitivity related infusion reactions related to the release of cytokines during and after the infusion. This delayed release of cytokines post-infusion incurs the risk of reactions even after the infusion is complete. Although most monoclonal antibodies currently used in clinical practice do not require mandatory post infusion monitoring, T-DM1 requires a post-infusion observation time of 90 minutes following the initial infusion and 30 minutes following subsequent infusions. Documented rates of T-DM1 infusion reactions are between 1-2%, with higher rates of infusion reactions associated with initial cycles. The rates of infusion reactions within the observation window need to be defined to determine the clinical necessity of a mandatory observation time.

Objective
Determine the rate and timing of infusion reactions in patients treated with T-DM1.

Methods
A retrospective evaluation of breast cancer patients that received at least two cycles of T-DM1 within the Mayo Enterprise and Health System sites will be included. Patients must have initiated their first cycle after September 11th, 2019 and before September 11th, 2023. Data collected will include the total number of T-DM1 infusions received, the severity and timing of any noted infusion reaction, supportive care administered for reactions, changes to premedications or infusion rate following reactions, history of trastuzumab reactions, and if treatment is used in adjuvant or metastatic setting. Measured endpoints will be overall rate of infusion reactions and rate of infusion reactions that occurred within the observation window. Data will be summarized using counts and percentages for categorical data and either means and standard deviations or medians and interquartile ranges for continuous data. Corresponding 95% exact binomial confidence intervals will be calculated for the reaction rates.

Results: Pending

Conclusions
The findings of this study will allow us to determine if the frequency of T-DM1 infusion reactions within current mandatory observation times.

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