Anti-PD-1 and regorafenib induce severe multisystem adverse events in microsatellite stability metastatic colorectal cancer: a case report.

There exists a dilemma in the treatment of microsatellite stability (MSS) metastatic colorectal cancer (mCRC) owing to limited therapeutic options. Based on the promising results of the REGONIVO trial, combination of anti-PD-1 and regorafenib could be applicable for this kind of patients. Here we first report a case of an MSS mCRC patient who received sinitilimab plus regorafenib as third-line treatment and suffered severe multisystem treatment-related adverse events including Grade 3 myocarditis, myositis, myasthenia gravis, dermatitis, hepatitis, etc. Fortunately, all these adverse events were reversed with administration of corticosteroids. Though evidence of tumor shrinkage was not found, CEA levels markedly decreased. Therefore, anti-PD-1 plus regorafenib might be optional for the MSS mCRC patients which requires special caution in the clinical practice.