Objectives: To determine the necessity of pelvic lymph node dissection for low-risk prostate cancer, we analyzed the incidence of lymph node invasion and the therapeutic value of pelvic lymph node dissection in low-risk prostate cancer patients. Methods: Medical records for 1268 patients undergoing open radical prostatectomy between January 2000 and December 2009 who had not undergone neoadjuvant therapy were retrospectively reviewed. Patients with low-risk disease (n=222; prostate-specific antigen <10ng/mL, biopsy Gleason score ≤6, clinical T1c or T2a) were classified according to whether they underwent pelvic lymph node dissection (pelvic lymph node dissection group, n=147) or did not (no pelvic lymph node dissection group, n=75). Pelvic lymph node dissection was carried out in a limited style, which included the external iliac vein and the obturator fossa. The incidence of lymph node invasion was determined and referred to the preoperative nomogram developed for Japanese patients (Japanese nomogram), Partin and Kattan nomograms. The 5-year biochemical recurrence-free survivals in both groups were analyzed. Results: Lymph node invasion in low-, intermediate- and high-risk disease was 0.7% (1/147), 1.2% (7/595) and 6.1% (23/374). The 5-year biochemical recurrence-free survival rates for patients with low-risk disease were 87.6% in the pelvic lymph node dissection group and 87.1% in the no pelvic lymph node dissection group (P=0.65, log-rank). No patients in the pelvic lymph node dissection group exceeded 2% of lymph node invasion risk with Japanese and Partin nomograms. With the Kattan nomogram, 22.4% (33/147) of the pelvic lymph node dissection group exceeded 2% of lymph node invasion risk, and one patient had documented lymph node invasion, but none exceeded 2.5%. Conclusions: Pelvic lymph node dissection can be spared at radical prostatectomy for low-risk disease, as its diagnostic and therapeutic value is poor.
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