A case of complete response to radiotherapy combined with durvalumab and tremelimumab in a patient with unknown primary hepatocellular carcinoma arising in the lumbar spine.

A 58-year-old man visited an orthopedic clinic complaining of pain in his right lower back and numbness in his lower limbs for one month. Imaging tests revealed a tumorous lesion from the left side of the second lumbar vertebra to the paraspinal muscles. CT-guided biopsy of the tumor was performed, and immunostaining results diagnosed hepatocellular carcinoma (HCC). Although the liver showed signs of chronic liver damage, no primary tumor was found within the liver or in other organs. Blood tests showed negative hepatitis virus markers for both HBV and HCV. The tumor markers AFP, AFP-L3, and DCP were high. Because he developed spinal cord compression syndrome due to a lumbar tumor, radiation therapy and denosumab administration were performed. Subsequently, systemic therapy with durvalumab plus tremelimumab was started. In the year following the start of treatment, the tumor has shrunk, and no new lesions have been observed. Tumor markers have also decreased. We have experienced a case of HCC in the lumbar spine without a primary tumor in the liver. This is a very rare case, and the combination therapy with durvalumab and tremelimumab resulted in a complete response, which we consider to be a valuable case.