Increasing rate of lymph node invasion in patients with prostate cancer treated with radical prostatectomy and lymph node dissection

Objectives

To investigate lymph node invasion (LNI) rates in prostate cancer (PCa) patients. Recent studies demonstrated an inverse stage migration in PCa patients toward more advanced and unfavorable diseases. We hypothesized that this trend is also evident in LNI rates, in PCa patients treated with radical prostatectomy (RP) and pelvic lymph node dissection (PLND).

Patients and methods

Within the Surveillance, Epidemiology, and End Results database (2004–2014), we identified patients who underwent RP and PLND. Annual trends of LNI rates and PLND extent were plotted. Univariable and multivariable logistic regression models tested the hypothesis that LNI rates are increasing annually, even after adjustment for clinical or pathological characteristics.

Results

Of 96,874 patients treated with RP and PLND, 4.1% (n = 4,002) exhibited LNI. The rate of LNI (2.5%–6.6%.), the mean (6.5–8.4) and median (5–6) number of removed lymph nodes increased during the study period. In multivariable logistic regression models, more contemporary year of diagnosis was associated with higher LNI rate, when year of diagnosis was modeled as a continuous, categorized or cubic spline variable, with adjustment for either clinical (prostate specific antigen, clinical tumor stage, and biopsy Gleason group) or pathological characteristics (pathologic tumor stage and Gleason group), as well as PLND extent (number of removed lymph nodes).

Conclusion

We confirmed the hypothesis about increasing LNI rate over time in RP patients. This observation implies an increasing rate of unfavorable PCa defined as LNI. This finding is novel for contemporary epidemiological North American or European databases.