Therapeutic value of lymph node dissection at radical prostatectomy: a population-based case-cohort study.
OBJECTIVE
• To examine the association between the number of lymph nodes removed in pelvic lymphadenectomy and the risk of prostate cancer death, particularly in low to intermediate risk prostate cancer patients.


METHODS
• Data on a subset of patients from a population-based case-cohort study was used to assess the effect of lymph node removal on prostate cancer-specific mortality. • The subset included in this report were those 281 patients from the parent study who were treated with prostatectomy and had a pelvic lymph node dissection and for whom we had a record of the number of nodes removed (the sub-cohort) and 41 patients fitting the same criteria who died of their prostate cancer within 10 years (the cases). • Study variables included number of lymph nodes removed, lymph node status, age, pre-treatment PSA, T category, Gleason score and use of hormonal therapy. • We ran a Cox proportional hazards regression analysis that accounted for the study design and allowed us to consider these patient and disease characteristics as potential confounders of the association of interest. • In a secondary analysis, the results were stratified by nodal status.


RESULTS
• The crude hazard ratio (HR), which is a measure of relative risk, was not statistically significantly associated with a reduction in the risk of prostate cancer mortality as the number of lymph nodes removed at PLND increased (HR: 0.97, 95% CI: 0.91-1.03). • None of the variables considered as potential confounders had an impact on the crude HR. Using two cut points to categorize the number of lymph nodes removed, one at 4 or more removed and the other at 10 or more removed resulted in HRs indicating a risk reduction of 25% in both cases, although these results were not statistically significant. • When we analyzed the association by pathological nodal status, we observed a possible increase in risk in the node-positive group (HR: 1.10, 95% CI: 0.86, 1.42), while those with negative lymph nodes may have benefited from increasing numbers removed (HR 0.95, 95% CI: 0.89,1.02).


CONCLUSIONS
• The results of this study indicate a possible therapeutic benefit of lymph node removal in node negative patients. Future research should focus on gaining a better understanding of the biologic mechanisms of a possible therapeutic benefit of PLND, particularly for those lower risk patients with histologically negative lymph nodes.
Division of Cancer Care and Epidemiology, Queen's Cancer Research Institute, Kingston, Canada.
Diana R
DR
Withrow
Julie M
JM
DeGroot
D Robert
DR
Siemens
Patti A
PA
Groome
D000368:Aged; D004812:Epidemiologic Methods; D006801:Humans; D008197:Lymph Node Excision / Q000379:methods*; D008198:Lymph Nodes / Q000473:pathology / Q000601:surgery*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011468:Prostatectomy / Q000379:methods*; D011471:Prostatic Neoplasms / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome