Presenting Author: Jennifer Hutchinson, PharmD, BCOP, Massachusetts General Hospital, Boston, MA
BACKGROUND: Pertuzumab and ado-trastuzumab emtansine (T-DM1) are HER2-targeted antibodies used for the treatment of breast cancer. Clinical trials report infusion-related reactions (IRRs) of 21% and 1.6%, respectively, which are significantly lower than with trastuzumab (40%). Despite this, FDA-recommended postinfusion observation times remain prolonged at 60 minutes and 90 minutes for initial doses of pertuzumab and T-DM1, respectively, and at 30 minutes for subsequent doses. Limited data exist on IRR characterization and the safety of reduced observation times, leading to potentially unnecessary monitoring and chair time.
OBJECTIVES: To evaluate the incidence and severity of IRR with pertuzumab and T-DM1 and to assess the safety of reduced observation times.
METHODS: We conducted a retrospective chart review of patients with breast cancer who received ≥1 dose of pertuzumab or T-DM1 between January 2022 and February 2025. The primary outcome was the incidence of IRRs within the first 3 doses. The secondary outcomes included the timing, management, and severity of IRRs per the Common Terminology Criteria for Adverse Events, version 5.0. A prospective review of patients who received treatment between March 2025 and August 2025 evaluated the incidence and severity of IRRs within the first 3 doses after the implementation of reduced observation times (30 minutes for initial doses, none for subsequent doses).
RESULTS: A total of 242 patients (69% received pertuzumab and 31% received T-DM1) were included in the initial retrospective review. For pertuzumab, 2 (1.2%) patients had a reaction after receiving the first dose and 1 (0.6%) patient each had a reaction after the second and third doses. The average grade of reaction was 2 (range, 1-3). The median time to reaction onset was 100 minutes (range, 80-120 minutes) from the start of the first infusion. No reactions occurred during the observation period for subsequent doses. For T-DM1, 5 (6.7%) patients reacted with the first dose; none of the patients had IRRs with subsequent doses. The average grade of IRR was 1 (range, 1-2). The median time to IRR onset was 86 minutes (range, 10-180 minutes) from the start of the first infusion. In our prospective review, a total of 58 patients (60% receiving pertuzumab and 40% receiving T-DM1) were included. None of the patients in either arm had IRRs with shortened observation times, resulting in a combined estimated chair time-savings of 47 hours per month.
CONCLUSION: In real-world practice, pertuzumab- and T-DM1–associated IRRs were infrequent, mild, and occurred primarily during infusion rather than in the observation period. Given the low incidence of IRR, we were able to safely implement standardized, shortened observation times, which were well tolerated and have resulted in significant chair time-savings. These findings support the re-evaluation of the current observation times to guide future practice standards.
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- Kadcyla (ado-trastuzumab emtansine) injection, for intravenous use [prescribing information]. Genentech; May 2025. Accessed September 17, 2025. www.gene.com/download/pdf/kadcyla_prescribing.pdf
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