Relative impact of lymph-node metastasis and seminal vesical invasion on oncologic outcomes following radical prostatectomy

Background: While both seminal vesicle (SVI) and lymph-node invasion (LNI) have been identified as adverse prognostic variables among men undergoing radical prostatectomy (RP), the relative impact of each of these features on subsequent oncologic outcomes has not been well defined. We assessed the impact of LNI on long-term oncologic outcomes among patients with SVI at RP. Methods: We reviewed 19,519 patients who underwent RP and identified 2043 with SVI. Metastasis-free (MFS), cancer-specific (CSS), and overall survival (OS) were estimated for patients with SVI, stratified by the presence and number of pelvic lymph node metastases. Cox proportional hazards models were used to evaluate the independent association of the number of metastatic nodes and lymph node density with oncologic outcomes among patients with SVI, controlling for age, year of surgery, margin status, preoperative PSA, pathologic Gleason score, extraprostatic extension, and use of adjuvant therapies. Results: At a median follow up of 12.1 years (IQR 7.0,18.6), 548 patients developed metastatic disease and 1331 died, including 406 who died from prostate cancer (PCa). We found that, among patients with SVI, the presence of a single positive lymph node was not associated with incrementally adverse oncologic outcomes compared to no nodal metastasis at RP, with 10-year MFS, CSS, and OS rates of 81.3% versus 78.3%(p = 0.18), 86.5% versus 89.8%(p = 0.32), and 72.8% versus 76.7%(p = 0.53), respectively. In contrast, on multivariable analyses, the presence of ≥2 metastatic nodes and a 20% lymph-node density cut off remained independently associated with worse survival. Conclusions: SVI represents an adverse pathologic feature such that the presence of a single positive pelvic lymph node did not further adversely impact prognosis. Meanwhile, a significant number of involved nodes was associated with decreased survival. These findings may aid in risk-stratification as well as clinical trial design for such high-risk patients following surgery.