1416P Recurrence of infusion-related reaction (IRRs) associated to avimantamab

Infusion-related reaction (IRR) are a common toxicty of amivantamab, with a high incidence during the first infusion (97%). However, subsequent injections are usually not affected, unless there is a delay in treatment for several weeks. We evaluate the risk of IRR after the resumption of amivantamab, based on the duration of the free treatment interval. This was a retrospective observational study to evaluate the recurrence of IRR in advanced non-small cell lung cancer patients treated with amivantamab and lazertinib in Gustave Roussy (2019-2023). Baseline characteristics of patients are summarized in the table. 24 patients were included, 12 (50%) presented IRR during the first infusion, and only one of them presented previous history of allergy. 9 patients had a temporary discontinuation of treatment, but only 2 had an IRR recurrence (these 2 had experienced an IRR during first cycle). Median time of treatment discontinuation was of 25.57 days for those patients without IRR recurrence and 44 days for those who presented it. Both patients with IRR recurrence had a temporary withdrawal due to another toxicity (at day 29 and 59 respectively) being of CTCAE grade 3 and 2 respectively. 5 patients (41.6%) needed corticoesteroids and 6 (50%) received antihistamines as treatment for the IRR. Only one patient required magnesium sulfate. A third IRR recurrence was experienced in both patients (grade 2 and 1 respectively), leading to permanent treatment discontinuation for one patient. None of the patients progressed to amivantamab and both are still alive.Table: 1416PGender (N) Female Male15 9Median age, Years (IQR)66 (39-81)Molecular profile (N) EGFR exon 19 EGFR exon 20 EGFR L858R MET overexpression MET exon 14 skipping mutation11 1 9 1 2Median number of previous lines (IQR)2 Open table in a new tab . Recurrence of IRR after the first episode is frequent and must be taken into account when reintroducing amivantamab after a temporary withdrawal of ≥1 month. IRR recurrence does not seem to have a detrimental impact on treatment efficacy.