An Increase in Gleason 6 Tumor Volume While on Active Surveillance Portends a Greater Risk of Grade Reclassification with Further Followup.

PURPOSE

We evaluated the relative risk of later grade reclassification and outcomes of patients in whom high volume Gleason 6 prostate cancer develops while on active surveillance.

MATERIALS AND METHODS

A prospectively maintained database was used to identify patients on active surveillance between 1998 and 2013. Tumor volume was assessed based on the number of positive cores and proportion of core involvement. The chi-square and Fisher exact tests were used for analysis as appropriate. The primary end point was the development of grade reclassification, defined as grade only and/or grade and volume at the event biopsy.

RESULTS

A total of 555 men met the study inclusion criteria. Mean followup was 46 months. Overall 70 patients demonstrated an increase in tumor volume at or after biopsy 2. Compared to those men never experiencing volume or grade reclassification, prostate specific antigen at diagnosis was not significantly different (p=0.95), but median prostate volume was smaller in patients who demonstrated volume reclassification (p <0.001). The incidence of pure volume reclassification was 6.8%, 6.1% and 7.8% at biopsy 2, 3 and 4, respectively. Men with volume reclassification were more likely to experience later grade reclassification than those without at 33.3% vs 9.3%, respectively (p <0.0001).

CONCLUSIONS

While Gleason 6 prostate cancer has a favorable natural history, it appears that patients on active surveillance who experience volume reclassification are at substantially higher risk for grade reclassification. Thus, urologists should pay close attention to tumor core involvement, and monitoring should be adjusted accordingly for early volume reclassification in younger men and those in good health.