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

Study Type – Diagnosis (case series) Level of Evidence 4 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.