Episode 15: Adding stereotactic radiotherapy to abiraterone acetate significantly delays disease progression in oligometastatic CRPC patients: the ARTO trial

In this new episode of ‘What’s New Doc’ in Prostate cancer, Prof Bertrand Tombal from the Cliniques Universitaires Saint-Luc in Brussels and Prof Steven Joniau from the University Hospitals Leuven discuss the results of the phase II ARTO trial, evaluating the added benefit of stereotactic radiotherapy (SBRT) in patients with oligometastatic, castration-resistant prostate cancer (CRPC) treated with abiraterone acetate and prednisone (AAP).¹

In ARTO, 157 patients with oligometastatic CRPC were randomly assigned to receive AAP alone, or concomitantly with SBRT targeting all the disease sites. For this study, oligometastatic disease was defined as three or less non-visceral metastatic lesions. Interestingly, the addition of SBRT to AAP led to a significant increase in the biochemical response rate (92% vs. 68.3%; OR[95%CI]: 5.34[2.05-13.88]; p= 0.001). Furthermore, this increased response rate also translated into a dramatic delay in the occurrence of disease progression, with a hazard ratio for progression-free survival (PFS) of 0.35 (95%CI: 0.21-0.57; p< 0.001).¹

Despite being just a phase II study, both Prof Tombal and Prof Joniau agree that these findings are truly practice changing. However, they also underscore that this impressive effect could only be achieved if all the disease sites were radiated. This implies the need for optimal medical imaging (e.g., PSMA-PET) in this setting.