- Gleason pattern 3 disease (Gleason score 6, now known as Gleason grade group 1) does not metastasize. In their molecular genetics, most Gleason pattern 3 cells resemble normal cells. In contrast, Gleason pattern 4 cells in most cases have the hallmarks of malignancy.
- High-volume pattern 3 disease is significant, not because it poses a threat to the patient, but because it is associated with an increased risk of coexistent higher-grade cancer. Thus, such patients require closer scrutiny, but don't need to be treated unless higher-grade cancer is identified.
- Any Gleason pattern 4 disease at baseline is associated with a significant increase in the risk of progression to metastatic disease. In the Toronto cohort, the patients with Gleason 3+4=7 disease at baseline had a 3.8× greater risk of metastasis at 15 years (20% vs 5%). Thus, patients with Gleason 7 cancer and a > 10–15-year life expectancy should in most cases be treated.
- Multiparametric MRI and biomarkers will likely expand the indications for surveillance-by identifying intermediate-risk patients with favorable-risk disease, and by reassuring low-risk patients that they are not harboring higher-risk cancer.