Although rare, there are cases within reported series of men with Gleason score (GS) ≤6 on radical prostatectomies that show pelvic lymph node (LN) metastases. However, there are no studies on whether pelvic LN metastases occur in tumors with GS ≤6 using the International Society of Urological Pathology (ISUP) updated GS system. We performed a search of the radical prostatectomy databases at 4 large academic centers for cases of GS ≤6. Only prostatectomies submitted and embedded in entirety with pelvic LN dissections were included. A combined total of 14,123 cases were identified, of which 22 cases had a positive LN. Histopathologic review of 19 cases (3 cases unavailable for review) showed higher grade than originally reported by the pathologists in all cases. Of the 17 pre-ISUP reviewed cases, 2 were upgraded to 4+3=7 with both cribriform and poorly formed glands. One case was upgraded to 4+3=7 with tertiary pattern 5 displaying cribriform glands, poorly formed glands, and cords of single cells. Eleven cases were upgraded to 3+4=7 with glomeruloid structures and small to large cribriform glands (1 of these also had features of ductal adenocarcinoma). Two cases had tertiary pattern 4 with small cribriform glands. One case had a prominent colloid component that would currently be graded as 4+5=9 because of large cribriform glands and solid sheets of cells within the mucin. Of the 2 post-ISUP cases, 1 demonstrated tertiary pattern 4, and the other showed GS 3+4=7 with irregular cribriform glands. Undergrading is the primary reason for LN positivity with GS ≤6, which has decreased significantly since the adoption of the ISUP grading system in 2005. Of over 14,000 totally embedded radical prostatectomies from multiple institutions, there was not a single case of a GS ≤6 tumor with LN metastases. In contrast to prevailing assumptions, GS ≤6 tumors do not appear to metastasize to LNs. Rather, Gleason pattern 4 or 5, as better defined by the current ISUP updated grading system, is required for metastatic disease.

Purpose

Gleason 6 (3+3) is the most commonly diagnosed prostate cancer among men with prostate specific antigen screening, the most histologically well differentiated and is associated with the most favorable prognosis. Despite its prevalence, considerable debate exists regarding the genetic features, clinical significance, natural history, metastatic potential and optimal management.

Materials and methods

Members of the Young Urologic Oncologists in the Society of Urologic Oncology cooperated in a comprehensive search of the peer reviewed English medical literature on Gleason 6 prostate cancer, specifically focusing on the history of the Gleason scoring system, histological features, clinical characteristics, practice patterns and outcomes.

Results

The Gleason scoring system was devised in the early 1960s, widely adopted by 1987 and revised in 2005 with a more restrictive definition of Gleason 6 disease. There is near consensus that Gleason 6 meets pathological definitions of cancer, but controversy about whether it meets commonly accepted molecular and genetic criteria of cancer. Multiple clinical series suggest that the metastatic potential of contemporary Gleason 6 disease is negligible but not zero. Population based studies in the U.S. suggest that more than 90% of men newly diagnosed with prostate cancer undergo treatment and are exposed to the risk of morbidity for a cancer unlikely to cause symptoms or decrease life expectancy. Efforts have been proposed to minimize the number of men diagnosed with or treated for Gleason 6 prostate cancer. These include modifications to prostate specific antigen based screening strategies such as targeting high risk populations, decreasing the frequency of screening, recommending screening cessation, incorporating remaining life expectancy estimates, using shared decision making and novel biomarkers, and eliminating prostate specific antigen screening entirely. Large nonrandomized and randomized studies have shown that active surveillance is an effective management strategy for men with Gleason 6 disease. Active surveillance dramatically reduces the number of men undergoing treatment without apparent compromise of cancer related outcomes.

Conclusions

The definition and clinical relevance of Gleason 6 prostate cancer have changed substantially since its introduction nearly 50 years ago. A high proportion of screen detected cancers are Gleason 6 and the metastatic potential is negligible. Dramatically reducing the diagnosis and treatment of Gleason 6 disease is likely to have a favorable impact on the net benefit of prostate cancer screening.

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Prostate Cancer Early Detection provide recommendations for prostate cancer screening in healthy men who have elected to participate in an early detection program. The NCCN Guidelines focus on minimizing unnecessary procedures and limiting the detection of indolent disease. These NCCN Guidelines Insights summarize the NCCN Prostate Cancer Early Detection Panel's most significant discussions for the 2016 guideline update, which included issues surrounding screening in high-risk populations (ie, African Americans, BRCA1/2 mutation carriers), approaches to refine patient selection for initial and repeat biopsies, and approaches to improve biopsy specificity.