Synergistic anti-tumor effects of zoledronic acid and radiotherapy against metastatic hepatocellular carcinoma.

A 72-year-old man with advanced hepatocellular carcinoma and decompensated hepatitis C virus-related cirrhosis suffered from a metastatic femoral fracture. After undergoing radiotherapy, he was only treated with supportive care, except for the administration of zoledronic acid (ZA). Thereafter, the initially elevated serum α-fetoprotein and des-gamma carboxyprothrombin levels declined to within the normal ranges. Hepatic and metastatic adrenal tumors, distant from the radiation field, exhibited a surprising regression. ZA is known to inhibit the activity of osteoclasts, bone-residential macrophages, and has been reported to have a direct anti-tumor effect. ZA may adjust the immunological milieu in tumor microenvironments by inhibiting the tumor-associated macrophages. Because radiotherapy can enhance the presentation of tumor-associated antigens, ZA and radiotherapy may exert synergistic anti-tumor effects.