Stereotactic radiosurgery for merkel cell carcinoma brain metastases.

In this report we propose a novel approach to treat merkel cell carcinoma (MCC) brain metastases and present a review of the literature in an attempt to establish a treatment algorithm and provide prognosis. MCC is a rare neuroendocrine malignancy affecting the aging population. This malignancy has a very aggressive behavior with frequent metastases. We report a 61-year-old man with a prior history of MCC who presented with diplopia. Brain MRI revealed a single right thalamic lesion consistent with metastasis. In the two weeks following GammaKnife stereotactic radiosurgery (Elekta, Stockholm, Sweden) the diplopia improved. A brain MRI demonstrated shrinkage of the tumor. From our literature search we found only six other patients with MCC brain metastases. The majority of these patients were treated with whole brain radiation in conjunction with chemotherapy. We propose that stereotactic radiosurgery can be used as a first line therapy for patients with MCC metastatic brain disease.