Long-term outcomes of prostate cancer patients with metastases in the anterior fat pad and pelvic lymph nodes: Nodal upstaging without worse long-term outcomes.

[BACKGROUND] The frequency and prognostic significance of prostate cancer (PCa) metastasis to the prostatic anterior fat pad (PAFP) remain unclear. We evaluated the incidence of lymph nodes and metastatic involvement within the PAFP and assessed the impact of PAFP lymph node metastasis on nodal staging accuracy and long-term outcomes in patients undergoing radical prostatectomy.

[METHODS] We retrospectively analyzed 4028 patients who underwent radical prostatectomy with concurrent PAFP and pelvic lymph node (PLN) dissection between January 2010 and May 2021. Lymph nodes within the PAFP and PLN specimens, along with relevant histopathologic features, were evaluated. Patients were stratified into three groups based on the location of lymph node metastasis: (Group 1) PAFP-only metastasis, (Group 2) PLN-only metastasis, and (Group 3) metastasis involving both regions. Biochemical recurrence-free survival and overall survival were compared, and Kaplan-Meier analysis and multivariable Cox regression were used.

[RESULTS] Among all patients, lymph nodes were identified in the prostatic anterior fat pad in 295 cases (7.30 %), of those, 23 patients had isolated PAFP lymph node metastasis (0.57 % of the entire cohort and 7.80 % of patients with PAFP lymph nodes). PLNs were reported in 3874 patients (96.18 %), of whom 70 patients had isolated PLN metastasis (1.73 % of the entire cohort and 1.8 % of patients with PLN). Nine patients (0.22 % overall) demonstrated metastatic involvement of both PAFP and PLN. The metastatic positivity rate for isolated metastasis was significantly higher in PAFP lymph nodes than in PLN (Z = 6.7), with a relative risk of 4.32 (95 % CI, 2.73-6.75). Biochemical recurrence occurred in 77.8 % of patients in Group 1, 72.7 % in Group 2, and 66.7 % in Group 3. All-cause mortality was observed in 21.7 %, 7.2 %, and 22.2 % of patients in Groups 1, 2, and 3, respectively. Kaplan-Meier analysis and multivariable Cox regression demonstrated no significant differences in biochemical recurrence-free survival or overall survival between groups. Excision of the prostatic anterior fat pad resulted in lymph node upstaging in approximately 1 % of all patients. Biochemical recurrence-free survival and overall survival were comparable between patients with isolated PAFP and isolated PLN metastases.

[CONCLUSIONS] Routine excision and pathological evaluation of the prostatic anterior fat pad during radical prostatectomy improve nodal staging by identifying otherwise unrecognized N1 disease, without an associated adverse impact on oncologic outcomes, compared with pelvic lymph node evaluation alone.