Upper limit of cancer extent on biopsy defining very low-risk prostate cancer

Objective: To investigate how much Gleason pattern 3 cancer prostate biopsy specimens may contain without an increased risk of undetected more aggressive cancer, compared with the risk for cancers fulfilling the National Comprehensive Cancer Network (NCCN) criteria for very low-risk prostate cancer.

Patients and methods: We identified 1286 men aged <70 years in the National Prostate Cancer Register of Sweden who underwent primary radical prostatectomy (RP) for stage T1c or T2 prostate cancer with Gleason pattern ≤3 only, prostate-specific antigen (PSA) level of <10 ng/mL and a PSA density of <0.15 ng/mL/mL. The association between the extent of cancer in the biopsies (the number and proportion of positive cores and the total cancer length in the cores in millimetres) and the likelihood of Gleason pattern 4-5 in the RP specimen was analysed with logistic regression.

Results: In all, 438 (34%) of the 1286 men had Gleason pattern 4-5 in the RP specimen. Increasing number and proportion of positive biopsy cores, as well as increasing biopsy cancer length were both significantly associated with increased risk of upgrading at RP in univariable analysis, but in multivariable analysis only biopsy cancer length remained significant. The 684 men with stage T1c and <8 mm cancer had similar risk of upgrading regardless of whether the number of positive biopsy cores was 1-2 or 3-4 (28% vs 27% risk); upgrading was more common among the remaining men (40%, P < 0.01).

Conclusions: Men aged <70 years with stage T1c prostate cancer and 3-4 biopsy cores with Gleason pattern 3 are not more likely to have undetected Gleason pattern 4-5 cancer than men with 1-2 cores with cancer, provided that the total biopsy cancer length is <8 mm. We propose that the definition of very low-risk prostate cancer is widened accordingly.