Radical prostatectomy (RP) is a common treatment for local prostate cancer. In this study, we determined the effects of lymph node (LN) dissection on the surgical outcomes of RP using data from the Medical Investigation Cancer Network (MICAN) study, a retrospective Japanese cohort study of patients who underwent RP between January 2010 and December 2020 in Ehime Prefecture.
The MICAN study comprised 3,463 participants (mean age at surgery 69 years, mean prostate-specific antigen (PSA) concentration 7.11 ng/ml) treated by open radical prostatectomy (n=292), laparoscopic RP (n=938), or robot-assisted RP (n=2,233). Of these participants, 3,090 who did not undergo preoperative hormonal therapy were included in the present study. We recorded LN dissection, 2012 Briganti Score (BS), the number of LNs affected, the number of metastases, and the recurrence of high PSA.
There were 1,949 participants with pN0, 73 with pN1, and 1,065 with pNx. LN dissection was recorded in the obturator nerve region, obturator nerve and external iliac region, obturator nerve and internal/external iliac region, the region below the crossing of the ureter, and the region below the common iliac region in 1,529, 143, 99, 146, and 19 participants, respectively. The respective mean numbers of dissected LNs were 5.9, 6.5, 11.4, 20.1, and 25.6, and the mean number across all the participants was 8.1. The surgical procedures were prolonged and blood loss increased with the extent of dissection. During a median observation period of 51.4 months, the 5-year high PSA recurrence-free survival was 76.6% for pN0, 19.3% for pN1, and 86.0% for pNx. When the number of dissected LN was categorized as <11 and >11, the high PSA recurrence-free survival rate tended to be better in the group with >11 nodes affected, although this trend was not significant. For pN1, the high PSA recurrence-free survival rate tended to be higher when the number of LNs affected was higher, and was higher when the number of LNs affected was ≤2. Among the participants, 1,642 had BS <5% and 1,658 had BS ≥5%. Furthermore, 958 (52.1%) participants had BS ≥5% when pN0 was present and 3 (4.2%) had BS <5% when pN1 was present. Participants with BS ≥5% also had lower high PSA recurrence-free survival rates when pN0 or pNx was present.
With respect to LN dissection following RP, there is no association between the number of LNs affected and the recurrence of high PSA. However, high PSA recurrence-free survival is superior if the number of LNs affected is ≥11, and in patients with pN1 and ≥2 positive nodes.