Tumor volume in insignificant prostate cancer: Increasing the threshold is a safe approach to reduce over-treatment

There are conflicting results in the literature regarding the tumor volume (TV) threshold that defines insignificant prostate cancer (PCa). In this study, we retrospectively evaluate the association of an increasing TV with biochemical recurrence (BCR) following radical prostatectomy (RP) in order to provide further clarification surrounding the TV threshold definition for insignificant PCa.

RP patients were recruited from January 2004 to December 2009. Inclusion criteria were localized (stage ≤pT2c, negative surgical margins) Gleason 6 PCa with a total TV of ≤2.50 cm(3) . BCR was the primary outcome and defined as a PSA of ≥0.1. All cases with BCR were re-evaluated by the pathologist with reassessment of tumor grade, pathological stage and surgical margin status.

From 1,636 patients, 178 men (10.9%) met all inclusion criteria. Ninety-six patients (53.9%) had a TV <0.5 cm(3) and 82 patients (46.1%) had a TV 0.5-2.5 cm(3) . Three out of 178 patients (1.7%) presented with BCR during follow-up. One of these had TV <0.5 cm(3) and two had TV 0.5-2.5 cm(3) . These three cases of BCR underwent re-review of pathology; one patient was found to have a positive surgical margin and one patient was upgraded to Gleason 3 + 4 = 7. The third patient was re-reported as having positive margins for a benign hyperplastic nodule (incomplete RP specimen). Subsequently, these three cases were excluded from final analysis as they did not fit inclusion criteria. Median follow-up duration was 84 months (IQR 70-102 months). On final analysis, there were no patients with BCR, corresponding with a final BCR rate of 0% for both patients with a TV of <0.5 cm(3) and 0.5-2.5 cm(3) .

Our results have shown that, with a median follow-up of 84 (IQR 70-102) months, patients in our cohort with localized Gleason 6 PCa with a total TV 0.5-2.5 cm(3) have a BCR rate of 0%. We would support a more liberal total TV threshold of 2.5 cm(3) for the further development of algorithms to identify patients suitable for active surveillance.