Acute Exacerbation of Pre-existing Cancer-Related Pain: An Atypical Presentation of an Amivantamab-Induced Infusion-Related Reaction.

Cancer-related pain affects more than 70% of patients with advanced cancer and it is mediated by tumor invasion and inflammatory cytokine-induced neural sensitization. Anticancer therapies may transiently exacerbate pain through treatment-related inflammatory responses. Amivantamab, an EGFR-MET bispecific antibody approved for EGFR-mutated non-small cell lung cancer, commonly causes infusion-related reactions (IRRs), typically with flushing or respiratory symptoms. We report a case of a 70-year-old woman with EGFR-mutated lung adenocarcinoma who developed a reproducible, transient exacerbation of pre-existing cancer-related pain during initial amivantamab infusions without any systemic abnormalities or clear evidence of radiologic progression. This suggests that acute pain flare is an atypical manifestation of amivantamab-induced IRR.