The Role of Local Prostate and Metastasis-Directed Radiotherapy in the Treatment of Oligometastatic Prostate Cancer

Abstract

The local ablative therapy for oligometastatic disease (OMD) has the potential to delay further metastases and improve survival. However, it has not been fully elucidated how prostate primary radiotherapy (PPR) and metastasis-directed radiotherapy (MDR) affect prognosis in each different OMD scenario. Herein, we tried to provide efficacy and future perspectives for MDR in oligometastatic prostate cancer. Patients diagnosed with prostate cancer between 2010 and 2019 and treated for OMD (≤5 active lesions), which occurred synchronously or metachronously, were included. All patients received MDR at all detected lesions (OMDRT). OMDRT which was performed as soon as OMD was detected was classified as early, and OMDRT for progressions after hormone therapy was classified as late. The primary endpoint was survival after OMDRT, and timing of progression after RT was also analyzed. A total of 82 patients with oligometastatic prostate cancer received OMDRT. Among 36 patients with synchronous OMD, 58% received PPR at diagnosis, and 64% received early OMDRT. Among 46 patients with metachronous OMD, 80% received early OMDRT, and 28 received sequential OMDRT for repetitive OMD events. With a median follow-up of 32 months after OMDRT, 54 patients experienced progression and 5-year survival was 78%. Survival was highest in patients with synchronous OMD and early RT (5-year 86%), and 5-year survival of patients with metachronous OMD and early RT was significantly higher than those with late RT (78% vs. 44%, p = 0.003). Survival of patients with synchronous OMD and PPR was significantly higher than those without PPR or with metachronous OMD (5-year 90% vs. 66%, p = 0.030), by delaying progressions (17.9 vs. 7.0 months, p = 0.005). Survival gain could be achieved through OMDRT in oligometastatic prostate cancer, especially in synchronous OMD status. Also, it was possible to improve the prognosis further when OMDRT was performed early and with PPR.