Palliative Radiotherapy for Multiple Liver Metastases of Merkel Cell Carcinoma: A Case Report.

Introduction: There have been few reports of the efficacy of palliative radiotherapy (RT) for liver metastases of Merkel cell carcinoma (MCC). A case of a patient with gastrointestinal symptoms and liver dysfunction caused by multiple liver metastases of MCC is presented. Palliative RT improved the symptoms and liver function, enabling the continuation of systemic therapy. Case Presentation: A 66-year-old woman presented with metastatic MCC. Palliative RT (20 Gy in 5 fractions) was administered to the metastases extending from thoracic vertebra 11 to lumbar vertebra 1, and metastases in the left lobe of the liver were unintentionally partially included in the irradiation field. After palliative RT, avelumab therapy was initiated, but she complained of nausea and loss of appetite. Subsequent evaluations showed liver dysfunction and rapid progression of liver metastases. Palliative RT (20 Gy in 5 fractions) was administered to the right lobe of the liver, avoiding overlap with the previously irradiated area. Two weeks after RT, the patient showed significant improvement in the symptoms and liver function. The patient experienced no significant adverse events. She continued avelumab treatment, but she died 2 months after palliative RT to the right lobe of the liver due to progression of the MCC. Conclusion: Palliative RT should be considered a treatment option for patients with MCC who develop symptomatic liver metastases.