Durable clinical remission of a skull metastasis under intralesional Viscum album extract therapy: Case report

BACKGROUND: Skull metastases are rare, they can eventually cause pain, and can invade the brain. Viscum album extracts (VAEs) are used as an adjuvant treatment in cancer. METHODS AND RESULTS: A 68‐year‐old patient with rectal cancer presented with lung metastases, and metastases to multiple bone sites, the chest wall, and the liver were later identified. Histological examination of one of the bone lesions revealed an additional thyroid carcinoma. An osteolytic parietal bone lesion progressed to a painful metastasis of the skull despite radiotherapy and chemotherapy. The VAEs were applied weekly into the metastasis, followed by pain relief and softening of the lesion. The lesion partially regressed (>50%) after 8 months of continued VAE treatment and remained stable for 2 years. CONCLUSION: This case shows a durable clinical remission of a skull metastasis under VAE. Further investigations of intratumoral VAE treatment seem worthwhile—especially in symptomatic skull metastases not responding to radiotherapy or systemic therapies.