Metastatic potential to regional lymph nodes with Gleason score ≤7, including tertiary pattern 5, at radical prostatectomy

Abstract

To determine the risk of pelvic lymph node (LN) metastases at radical prostatectomy (RP) for Gleason score (GS) ≤7: 3 + 3 = 6 (grade group [GG]1); 3 + 4 = 7 (GG2); 3 + 4 = 7 (GG2) with tertiary pattern 5 (T5); 4 + 3 = 7 (GG3); 4 + 3 = 7 (GG3) with T5, using the 2014 modified Gleason grading system and the novel GG system. We searched our RP database to indentify cases of GS ≤7 prostate cancer with simultaneous pelvic LN dissection (PLND) in the period between 2005 and 2014. Since 2005, we have graded all glomeruloid and cribriform cancer as Gleason pattern 4 and have graded mucinous adenocarcinoma based on the underlying architectural pattern, consistent with the 2014 modified Gleason grading system. All RPs were embedded in entirety, including the PLND. A total of 7 442 cases were identified, of which 73 had at least one positive LN (+LN). The incidence rates for regional LN metastases at RP for 3 + 3 = 6 (GG1), 3 + 4 = 7 (GG2), 3 + 4 = 7 (GG2) with T5, 4 + 3 = 7 (GG3) and 4 + 3 = 7 (GG3) with T5 were 0, 0.6, 0.4, 4.3 and 6.3%, respectively. There was a statistically significant difference in risk of +LNs at RP between the grade groups, as defined by the novel GG system. There was no statistically significant difference in risk of +LNs at RP for men with 3 + 4 (GG2) vs 3 + 4 (GG2) with T5 and for men with 4 + 3 (GG3) vs 4 + 3 (GG3) with T5. Non-pelvic LN involvement was identified in 0.2% of all RP cases. Two patients with GS 3 + 4 = 7 with <5% pattern 4 experienced LN metastases. This study supports our previous finding that men with GS 6 (GG1) at RP have no risk of LN metastases. These findings also support the 2014 revisions to the Gleason grading system where 3 + 3 with T4 (2005 modified grading system) is now considered 3 + 4 (GG2), with a comment on percent pattern 4, because <5% pattern 4 increases the risk of LN metastases. It also supports keeping 3 + 4 (GG2) with T5 (<5% pattern 5) and 4 + 3 (GG3) with T5 with their respective grade groups, with a notation of T5 because the <5% higher grade component did not increase the risk of LN metastases within a given GG. Our findings highlight that 3 + 4 (GG2) and 4 + 3 (GG3), even with a 5% higher grade component, are distinct groups with respect to LN metastases and should not be combined under the umbrella designation of GS 7 as is often the case in the literature with the Gleason grading system.