National Comprehensive Cancer Network Practice Guidelines 2011: Need for More Accurate Recommendations for Pelvic Lymph Node Dissection in Prostate Cancer

Purpose: The 2011 NCCN (National Comprehensive Cancer Network) guidelines for prostate cancer recommend pelvic lymph node dissection at radical prostatectomy in all individuals with a nomogram predicted lymph node invasion probability of 2% or greater. We examined the ability of these guidelines to correctly predict lymph node invasion in patients treated with extended pelvic lymph node dissection. Materials and Methods: We examined 3,064 consecutive patients treated with radical prostatectomy and extended pelvic lymph node dissection between 2000 and 2010. We formally validated the NCCN guideline nomogram using discrimination, calibration and decision curve analysis as benchmarks. Moreover the performance characteristics of the 2% nomogram cutoff as well as other cutoff values (range 1% to 10%) were tested. Results: Overall 10.0% of patients had lymph node invasion. The discrimination accuracy of the NCCN guideline nomogram was 79.8%, with a maximum underestimation of the lymph node invasion risk of 41.2%. On decision curve analysis the NCCN nomogram fared better than not performing pelvic lymph node dissection in all patients. However, in the prediction range between 0% and 9% the nomogram did not fare better than performing pelvic lymph node dissection in all patients. The use of the 2% cutoff would allow the avoidance of 49.3% of pelvic lymph node dissections, at the cost of missing 20.3% of patients with lymph node invasion. Conclusions: The NCCN nomogram tends to significantly underestimate the real lymph node invasion rate. Moreover the use of the currently recommended cutoff of 2% to trigger pelvic lymph node dissection might not be appropriate.