Psoriasis induced by first‑line pembrolizumab in metastatic non‑small cell lung cancer: a case report

: Therapeutic options for non-small cell lung cancer (NSCLC) have changed with the introduction of immune checkpoint inhibitors. Immunotherapy is generally well tolerated, but can also be associated with severe adverse events, such as the development of new autoimmune diseases. In patients without a history of autoimmune diseases, psoriasis caused by immunotherapy treatment is rarely described in the literature. The present study describes the case of a 68-year-old man with metastatic NSCLC that started chemoimmunotherapy with carboplatin plus pemetrexed plus pembrolizumab. After two cycles of therapy, the patient developed a G3 maculopapular rash. Biopsy confirmed psoriasis and pembrolizumab treatment was discontinued. At the last follow up, the patient was still on maintenance therapy with pemetrexed alone, which is well tolerated. Psoriasis has rarely been reported as an immune-related adverse event. Although the patient had to stop the immunotherapy treatment, the patient is still exhibiting a response to it. Notably, it has previously been described how skin toxicities are associated with a better outcome. Other studies need to be conducted to identify the risk and predictive factors associated with severe immune adverse events and objective response.