Radical prostatectomy findings in patients predicted to have low-volume/low-grade prostate cancer diagnosed by extended-core biopsies: an analysis of volume and zonal distribution of tumour foci

OBJECTIVE To measure total tumour volume (TTV) and dominant TV (DTV) in radical prostatectomy (RP) specimens from patients predicted to have low-volume, low-grade (LV/LG) prostate cancer, as this entity can be predicted from biopsy findings and prostate-specific antigen (PSA) level, but tumour under-sampling remains a challenge in active surveillance programmes. PATIENTS AND METHODS This was a retrospective study from an academic centre, of men with prostate cancer treated from 2000 to 2007, with a PSA level of < 10 ng/mL and one core of cancer from an extended scheme showing either Gleason score (GS) 3 + 3 of < 3.0 mm or 3 + 4 of < 2.0 mm. All men had RP, and the TTV, DTV, tumour location, pathological GS and stage were measured. RESULTS Of 3055 RPs, 66 (2.1%) met the inclusion criteria. The core with cancer was from a sextant and alternative site in 26 (39%) and 40 (61%) patients, respectively. A pathological GS 3 + 3 or 3 + 4 was assigned to 94%, while 6% were GS >= 4 + 3; all 66 tumours were organ-confined. The median (range) TTV and DTV were 0.15 (0.0008-5.06) and 0.14 (0.0008-5.04) mL, respectively. The median number of tumour foci was 3 (1-7), being unifocal in 17/66 (26%) and multifocal in 49/66 (74%). The transition zone was involved in 29% of unifocal and 71% of multifocal tumours. Of all 66 patients, the TTV was < 0.5 mL in 47 (71%), and of 59 patients with biopsy GS 3 + 3, 33 (56%) had a TTV of < 0.5 mL and pathological GS 3 + 3. Of 19 patients with a TTV of >= 0.5 mL, the median TTV was 1.06 (0.51-5.05) mL, with tumour foci of transition zone origin in 16 (84%). The study was limited by its retrospective design and small sample size. CONCLUSIONS Using conservative selection criteria for predicting LV/LG cancer, RP specimens showed organ-confined disease in all cases, upgrading to GS >= 4 + 3 in 6%, and TTV < 0.5 mL in 71% of cases. The transition zone is a common location of under-sampled disease.