The impact of locoregional treatments for metastatic castration resistant prostate cancer on disease progression. real life experience from a multicenter cohort

Background: Available data on medical treatment of metastatic castration resistant prostate cancer (mCRPC) support the use of more than one therapy line to delay chemotherapy. We evaluate in a longitudinal real life multicenter cohort, the oncological outcome of mCRPC patients treated with Abiraterone Acetate (AA) and Enzalutamide (EZ) in a chemo-naïve setting, who received locoregional treatments for subsequent development of oligorecurrent disease. Methods: We prospectively collected data on chemo-naïve mCRPC patients, who received either AA or EZ as first or second line treatment between Oct-2012 and Nov-2020 at 5 centers. High-volume disease at mCRPC onset was defined as bulky positive nodes (≥5 cm) or more than 6 bone metastases. Survival probabilities were computed at 12, 24, 48 and 60 months after treatment start. The impact of loco-regional treatments on progression free survival (PFS) were assessed with the Kaplan-Meier method and the log-rank test was applied. Results: Overall, 117 chemo-naive mCRPC patients received a first line therapy. Fifty-seven (48.7%) patients received AA and 60 (51.3%) received EZ. Eight (6.7%) patients underwent salvage chemotherapy after first line failure. Overall, 28 patients shifted to a second line therapy. Two-yr progression-free, cancer-specific and overall survival probabilities were 65.5%, 82.2% and 78.4% respectively. Since diagnosis of mCRPC, oligo progression occurred in 25 patients who received stereotactic radiation therapy (23/25, 92%) focused on metastasis (4 nodal sites and 19 bones) or salvage lymph node dissection (2/25, 8%). At Kaplan-Meier analysis, patients with low volume disease displayed higher PFS probabilities (log rank p = 0.009) and in this subgroup of patients loco-regional treatments had a significant impact on PFS (p = 0.048), while it was negligible in the whole cohort and in patients with high volume disease (p = 0.6 and p = 0.75). Conclusions: Low-volume mCRPC patients are exposed to improved PFS and seem to benefit from locoregional treatments.