Metastatic Prostate Cancer: Impact of Site on Oncological Outcomes in Japanese Patients.

INTRODUCTION: To investigate the site of metastasis and progression to castration-resistant prostate cancer (CRPC) following treatment of patients with metastatic prostate cancer who were diagnosed and treated at our hospital. METHODS: We retrospectively examined the metastasis status and treatment response of patients with metastatic prostate cancer who were histologically diagnosed between the opening of our hospital in June 2015 and March 2025. RESULTS: A total of 139 patients with metastatic prostate cancer visited our hospital and were diagnosed with the condition. CRPC-free survival was significantly correlated with the bone metastasis volume (EOD 0 and 1 vs EOD 2 to 4) (P = 0.0000477), volume categories (P = 0.00196), risk categories (P = 0.00231), and PSA levels below/not below 0.2 ng/mL following ADT (P = 4.18 × 10-16); however, it was not significantly correlated with the biopsy Gleason grade group (GG) (GG5 vs GG<5) (P = 0.324) or lung metastasis (P = 0.894). None of the eight patients with lung metastases who were without bone metastases progressed to CRPC during the observation period following androgen deprivation therapy (ADT). There was a significant difference in CRPC-free survival between patients with lung metastasis but without bone metastasis (sample size: 8) and those with other metastasis sites but without lung metastasis (sample size: 131) (P = 0.025). DISCUSSION AND CONCLUSION: In our data on patients with metastatic prostate cancer, factors influencing the prognosis were: the extent of bone metastasis and responsiveness of PSA levels to initial treatments such as ADT. Factors such as GG at the time of biopsy or presence of lung metastases did not significantly impact the prognosis. Our data suggest that patients with lung metastases, but without bone metastases, may have a relatively favorable prognosis. New prognostic evaluation indicators are needed.