Clinical characteristics and prognostic factors of low metastatic burden prostate cancer with non-regional lymph node metastases: role of cytoreductive radiotherapy?

Abstract

Background: Low metastatic burden prostate cancer (LMBPC) is a special transitional clinical status between localized and disseminated disease, but the clinical prognostic factors and potential therapeutic interventions of those with non-regional lymph node metastases (NRLNM) remain less understood. We aim to explore the prognostic factors and investigate the potential treatment strategy for LMBPC patients with NRLNM.

Methods: There were 88 patients retrospectively identified. Kaplan-Meier method and Cox proportional hazards model were used for prognostic analyses. Patients receiving non-regional lymph node (NRLN) radiotherapy (NRLN RT group) after prostate-directed local therapy were matched to patients without NRLN RT (control group) by propensity score matching (PSM).

Results: The majority of patients had Gleason score >8 (61.4%), retroperitoneal metastases (93.2%), upward NRLNM (78.4%) and hormone-sensitive prostate cancer (HSPC) (68.2%) at diagnosis. Patients with upward NRLNM showed better survival outcome (75.4 vs. 32.8 months, P=0.04). HSPC [hazard ratio (HR) =0.32, P=0.003], bone metastases (HR =3.79, P<0.001), androgen-receptor-axis-targeted agents (ARATAs) (HR =0.40, P=0.007), and notably, NRLN RT (HR =0.23, P=0.001) were independent prognostic factors of overall survival (OS). The median follow-up was 43.3 months. The prostate-specific antigen (PSA) response and median progression-free survival (PFS) after NRLN RT were 70.6% and 29.5 months. The 4-year OS for NRLN RT group and control group were 62% and 46% (P=0.04). After PSM, NRLN RT was still associated with improved OS (HR =0.39, P=0.04). No grade ≥3 NRLN RT-related adverse event was observed.

Conclusions: Upward NRLNM was the main pattern for LMBPC with NRLNM and associated with better clinical outcome. HSPC, bone metastases, ARATAs and NRLN RT were independent prognostic factors. Applying cytoreductive RT to NRLNM may benefit LMBPC patients. Further studies are still needed.