Oncologic outcomes in men with metastasis to the prostatic anterior fat pad lymph nodes: a multi-institution international study

BACKGROUND: The presence of lymph nodes (LN) within the prostatic anterior fat pad (PAFP) has been reported in several recent reports. These PAFP LNs rarely harbor metastatic disease, and the characteristics of patients with PAFP LN metastasis are not well-described in the literature. Our previous study suggested that metastatic disease to the PAFP LN was associated with less severe oncologic outcomes than those that involve the pelvic lymph node (PLN). Therefore, the objective of this study is to assess the oncologic outcome of prostate cancer (PCa) patients with PAFP LN metastasis in a larger patient population. METHODS: Data were analyzed on 8800 patients from eleven international centers in three countries. Eighty-eight patients were found to have metastatic disease to the PAFP LNs (PAFP+) and 206 men had isolated metastasis to the pelvic LNs (PLN+). Clinicopathologic features were compared using ANOVA and Chi square tests. The Kaplan-Meier method was used to calculate the time to biochemical recurrence (BCR). RESULTS: Of the eighty-eight patients with PAFP LN metastasis, sixty-three (71.6 %) were up-staged based on the pathologic analysis of PAFP and eight (9.1 %) had a low-risk disease. Patients with LNs present in the PAFP had a higher incidence of biopsy Gleason score (GS) 8–10, pathologic N1 disease, and positive surgical margin in prostatectomy specimens than those with no LNs detected in the PAFP. Men who were PAFP+ with or without PLN involvement had more aggressive pathologic features than those with PLN disease only. However, there was no significant difference in BCR-free survival regardless of adjuvant therapy. In 300 patients who underwent PAFP LN mapping, 65 LNs were detected. It was also found that 44 out of 65 (67.7 %) nodes were located in the middle portion of the PAFP. CONCLUSIONS: There was no significant difference in the rate of BCR between the PAFP LN+ and PLN+ groups. The PAFP likely represents a landing zone that is different from the PLNs for PCa metastasis. Therefore, the removal and pathologic analysis of PAFP should be adopted as a standard procedure in all patients undergoing radical prostatectomy. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12894-015-0070-1) contains supplementary material, which is available to authorized users.