Phase II Randomized Trial of Radiation Therapy in Oligometastatic mCRPC Prostate Cancer (ARTO)

Metastatic castration resistant prostate cancer causes approximately 258400 deaths annually worldwide. In the presence of metastatic disease, systemic treatment remains the main clinical option. However, since the introduction of highly sensitive imaging techniques, a new clinical entity of metastatic patients with a limited number of lesions has been defined: oligometastatic patients. Although a clear benefit has yet to be demonstrated in this group of patients, the use of stereotactic body radiotherapy (SBRT) or other local therapies directed against all active lesions has been suggested as a possible salvage treatment. Irradiation of metastatic foci may delay the emergence of castration resistance because irradiation is effective against both ADT¬ sensitive and ADT ¬resistant prostate cancer cells as shown in re-biopsy studies. Stereotactic body radiation therapy has been used in this setting to defer the initiation of ADT in patients with oligometastatic prostate cancer with notable results. Abiraterone acetate is a first class inhibitor of cytochrome P ¬450c17, a critical enzyme in extragonadal and testicular androgen synthesis. Abiraterone plus low dose prednisone improves survival in patients with metastatic castration ¬resistant prostate cancer who have already received docetaxel and the combination therapy has received regulatory approval for this indication. Furthermore, Abiraterone acetate is approved also in patients who did not undergo to docetaxel chemotherapy, after the results from the COU-AA 302 study; Results from this phase III trial confirmed the benefit in chemo-naïve patients treated with abiraterone acetate both in terms of overall and radiological progression free survival, if compared to placebo. In oligometastatic CRPC, the rationale to use SBRT is that the addition of a local ablative treatment could improve disease control in mCRPC patients treated with a systemic therapy. The current phase II randomized trial,"Ablative Radiation Th