Continuous versus discontinuous tumor involvement: A dilemma in prostate biopsy quantitation

No consensus has been reached for an optimal method of quantifying discontinuous tumor foci separated by intervening benign tissue on prostate biopsy (PBx). We examined sets of PBx, where cancer involved only one core, and corresponding radical prostatectomy (RP) specimens.

Cases were divided into 3 groups-Group 1 (n = 80): <3 mm in end-to-end tumor measurement (continuous/discontinuous); Group 2 (n = 22): ≥3 mm in tumor length (continuous); and Group 3 (n = 15): ≥3 mm in end-to-end tumor measurement (discontinuous). The rate of Gleason score ≥7 was considerably lower in Group 1 (9%/30% on PBx/RP) than in Group 2 (50% [P < 0.001]/59% [P = 0.015] on PBx/RP) or Group 3 (40% [P = 0.005]/46% [P = 0.237] on PBx/RP). pT2 disease was significantly more often found in Group 1 (88%) than in Group 2 (68%, P = 0.049) or Group 3 (60%, P = 0.018). Surgical margin was significantly more often positive in Group 3 (27%) than in Group 1 (5%, P = 0.020), but not Group 2 (9%, P = 0.198). Moreover, estimated cancer volume (cc, mean ± SD) was significantly smaller in Group 1 (1.89 ± 1.98) than in Group 2 (3.56 ± 2.92, P = 0.026) or Group 3 (3.44 ± 2.02, P = 0.013). Kaplan-Meier analysis revealed higher risks of biochemical recurrence after RP in Group 2, compared with Group 1 (P = 0.001) or Group 3 (P = 0.096). In 93 patients with biopsy Gleason score 6 cancer, higher rates of pT2+/3 disease (P = 0.023) and positive margin (P = 0.026), as well as larger cancer volume (P = 0.063), on RP were still seen in Group 3, compared with Group 1, but their differences were not statistically significant between Group 2 and Group 3.

Linear quantitation including intervening benign tissue on PBx may more precisely predict the actual tumor extent.