Can palliative radiotherapy influence prostate-specific antigen response in patients with castrate-resistant prostate cancer treated with systemic therapy (chemotherapy or abiraterone)?—a report of three cases

Palliative radiotherapy (pRT) is primarily employed for palliation of bone pain in patients with castrate-resistant prostate cancer (CRPC). However, evidence that pRT influences prostate-specific antigen response in patients with CRPC on systemic therapy is lacking. We describe three cases of CRPC progressing after treatment with docetaxel (n=2) and abiraterone (n=1), who responded unusually after pRT for bone pain with the development of a significant biochemical response and restoration of response to systemic therapy. The possibility of pRT influencing metastatic disease in CRPC has not been previously reported, and raises the possibility of radiation-induced modulation of anti-tumor immune response mechanisms that may play a role in the restoration of response to systemic treatment.