P164 Cutaneous toxicities occurring during amivantamab treatment: the experience of a single large specialist institution

Abstract Amivantamab is a bispecific antibody targeting EGFR (epidermal growth factor receptor) and MET (mesenchymal-epithelial transition factor). It was recently approved by NICE as first-line combination therapy with lazertinib for non-small cell lung cancer (NSCLC). It is also used in glioblastoma and oropharyngeal squamous cell carcinoma. Dermatological adverse events (dAEs) are common and may impact quality of life and necessitate dose reductions or treatment discontinuation. This single-centre, retrospective observational study aimed to asses treatment efficacy to inform best-practice clinical guidelines at a tertiary referral oncology centre. Patient demographics, incidence, clinical features, management and survival outcomes of amivantamab-associated dAEs were evaluated from February 2021 to June 2025. In total 60 patients were included (mean age 60 years). Acneiform rash occurred in 80% of patients, paronychia in 60%, scalp involvement in 53%, mucositis in 25% and finger fissuring in 20%. Amivantamab dose reductions were required in 15% and treatment discontinuation in 7%. Among patients with paronychia, 64% developed grade 3 toxicity. Prophylactic skincare regimens did not reduce the incidence of paronychia. Partial and complete response rates in patients with paronychia were 35% and 2%, respectively, compared with 20% and 0% in patients without paronychia (P = 0.18). Scalp involvement occurred in 56% (15 of 27) of patients receiving prophylactic antibiotics, vs. 52% (17 of 33) without (P = 0.76), and in 50% (14 of 28) of patients using prophylactic skincare vs. 56% (18 of 32) of those who did not (P = 0.63). The incidence of acneiform rash was similar with and without antibiotic prophylaxis (81%, 22 of 27 vs. 79%, 26 of 33; P = 0.80), with only 10% developing grade 3 toxicity. Effective management of amivantamab-associated dAEs is crucial as they are experienced by most patients. They impact quality of life and may necessitate treatment modifications. A multidisciplinary approach is to optimize effective management of dAEs with continued cancer control.