Validation of TNM classification for metastatic prostatic cancer treated using primary androgen deprivation therapy.

e604 Background: The current tumor–node–metastasis (TNM) classification system has been used for many years. The prognosis of patients with metastatic prostate cancer (mPC) treated using primary androgen deprivation therapy (PADT) was analyzed according to the TNM classification. Methods: A total of 5,618 cases with lymph node metastases only (N1M0), non-regional lymph node metastasis (M1a), bone metastasis (M1b), and distant metastasis (M1c) were selected from the Japanese Study Group of Prostate Cancer database. Overall survival (OS), cancer-specific survival (CSS), and progression-free survival (PFS) rates were calculated using Kaplan–Meier analysis. The influence of clinical variables on patient prognosis was evaluated using the Cox’s proportional hazard regression model. Results: Regarding age, patients with M1b tumors were significantly older than were those in the other groups. Prostate-specific antigen (PSA) levels tended to increase as the stage progressed. The Gleason score (GS) was significantly higher in the M1a group compared with the other groups. The 5-year OS was 76.0 % in the N1M0, 57.5 % in M1a, 54.0 % in M1b, and 40.0 % in M1c cases. The 5-year CSS was 83.2 % in the N1M0, 69.0 % in M1a, 63.1 % in M1b, and 51.5 % in M1c cases. The 5-year PFS was 38.8 % in the N1M0, 23.0 % in M1a, 23.0 % in M1b, and 16.6 % in M1c cases. OS, CSS, and PFS declined as the stage progressed; however, there were no statistically significant differences between M1a and M1b cases. Among the patients in the M1b group, the 2,445 cases of N0M1b and the 1,607 cases of N1M1b were compared. OS, CSS and PFS were all significantly worse in N1M1b compared with N0M1b. Multivariate analysis revealed that OS and CSS were worse in patients with a GS ≥ 8, and that combined androgen blockade (CAB) treatment provided better OS than non-CAB treatments at any tumor stage. However, OS and CSS were worse in individuals with a PSA > 100 ng/ml only in M1b. Conclusions: Patient prognosis worsened with stage progression. Each PC cell that develops bone or lymphoid metastasis may exhibit different characteristics. CAB is recommended as the primary treatment for mPC.