Stratifying prostate cancer patients by relative lymph node involvement: population- and modeling-based study

Contemporary Incidence and Outcomes of Prostate Cancer Lymph Node Metastases

PURPOSE

The incidence of localized prostate cancer has decreased with shifts in prostate cancer screening. While recent population based studies demonstrated a stable incidence of locoregional prostate cancer, they categorized organ confined, extraprostatic and lymph node positive disease together. However, to our knowledge the contemporary incidence of prostate cancer with pelvic lymph node metastases remains unknown.

MATERIALS AND METHODS

We used SEER (Surveillance, Epidemiology and End Results) data from 2004 to 2014 to identify men diagnosed with prostate cancer. We analyzed trends in the age standardized prostate cancer incidence by stage. The impact of disease extent on mortality was assessed by adjusted Cox proportional hazard analysis.

RESULTS

During the study period the annual incidence of nonmetastatic prostate cancer decreased from 5,119.1 to 2,931.9 per million men (IR 0.57, 95% CI 0.56-0.58, p <0.01) while the incidence of pelvic lymph node metastases increased from 54.1 to 79.5 per million men (IR 1.47, 95% CI 1.33-1.62, p <0.01). The incidence of distant metastases in men 75 years old or older reached a nadir in 2011 compared to 2004 (IR 0.81, 95% CI 0.74-0.90, p <0.01) and it increased in 2012 compared to 2011 (IR 1.13, 95% CI 1.02-1.24, p <0.05). The risk of cancer specific mortality significantly increased in men diagnosed with pelvic lymph node metastases (HR 4.5, 95% CI 4.2-4.9, p <0.01) and distant metastases (HR 21.9, 95% CI 21.2-22.7, p <0.01) compared to men with nonmetastatic disease.

CONCLUSIONS

The incidence of pelvic lymph node metastases is increasing coincident with a decline in the detection of localized disease. Whether this portends an increase in the burden of advanced disease or simply reflects decreased lead time remains unclear. However, this should be monitored closely as the increase in N1 disease reflects an increase in incurable prostate cancer at diagnosis.

Stratifying prostate cancer patients by relative lymph node involvement: population- and modeling-based study

It is estimated that about 10% of new prostate cancer (PCa) cases are lymph node‐positive (LN+). We have previously discussed the role of the inflection point (IP) of an inverse Gompertzian survival curve as a surrogate for disease incurability. In this study, we aimed to stratify curability of different patient cohorts with pathologically positive lymph nodes through modeling survival curves by different percentages of LN involvement (%LN+) postoperatively and calculating associated IPs. From the Surveillance, Epidemiology, and End Results (SEER) database, we selected LN+ PCa patients undergoing radical prostatectomy. Modeling of relative survival curves using inverse Gompertzian kinetics for increasing value of maximal %LN+ involvement allowed stratification of cohort into groups with <10%, 10–40%, and greater or equal to 40% of LN+ out of all LNs sampled. Data were retrieved for 5903 patients. For the entire cohort, relative survival was 96%, 87%, and 76% at 5, 10, and 15 years, respectively. For %LN +, <10% the IP was about 27 years postoperatively. Patients with 10–40% LN+ had an IP at about 10 years; for those with more than 40% LN+, the IP was 7 years. A 10‐year relative survival decreases from 97% for <10% LN+ to 71% for more than 40% LN+. While better therapies for LN + PCa are badly needed, this patient cadre is not homogenous and should be stratified by %LN+ in future clinical trials.