Severe Skin Toxicity Caused by Sequential Anti-PD-1 Antibody and Alectinib in Non-small-cell Lung Cancer: A Report of Two Cases and a Literature Review

Immune checkpoint inhibitors (ICIs) have demonstrated marked efficacy in some cancer patients, but they may cause various severe immune-related adverse events. Alectinib is a second-generation anaplastic lymphoma kinase (ALK)-tyrosine kinase inhibitor (TKI) approved for ALK-rearranged non-small-cell lung cancer (NSCLC). Alectinib is said to be safer than other TKIs. We conducted an investigator-initiated trial of alectinib, which also has RET kinase-inhibitory activity, against RET-rearranged NSCLC. Two RET-rearranged NSCLC patients experienced severe skin toxicity with alectinib after first undergoing anti-PD-1 antibody treatment with an ICI. These findings suggest that we should carefully follow patients for adverse effects of targeted drugs following ICI treatment.