Definition of Insignificant Tumor Volume of Gleason Score 3+3=6 (Grade Group 1) Prostate Cancer at Radical Prostatectomy - Is it Time to Increase the Threshold?

To investigate tumor volume (TV) of insignificant Gleason score 3+3=6 (Grade Group 1) prostate cancer with contemporary grading.

We studied 439 consecutive radical prostatectomies with Gleason score 3+3=6 (Grade Group 1) cancer entirely submitted for histologic examination.

Four-hundred-and-seven (92.7%) cases were organ-confined (pT2), 17 (3.9%) had positive margin at apex (pT2+), and 15 (3.4%) had extraprostatic extension (EPE)(pT3a), 10 focal and 5 non-focal. pT2 and pT3 cases did not differ by age or gland weight. When total TV was <0.5 cm(3), there were 6/311 (1.9%) tumors with EPE and 6/311 (1.9%) with tumor at the margin at the apex for a total of 12/311 (3.8%) significant cancers. TVs between 0.5-1.0 cm(3) and 1.0-2.0 cm(3) had similar incidences of significant cancers. With TV between 0.5-2.0 cm(3), there were 5/108 (4.6%) cases with EPE and 7/108 (6.5%) with pT2+ at the apex for a total of 12/108 (11.1%) significant cancers. The incidence of significant cancer increased further with TV >2.0 cm(3).

Only 3.8% of <0.5 cm(3) Gleason score 3+3=6 (Grade Group 1) cancers had EPE or extended apically where surgical removal was not possible. In contrast, 11.1% of cancers 0.5-2.0 cm(3) had these adverse features and would not have been tumors amenable for active surveillance. Our data indicate that increasing threshold above 0.5 cm(3) is associated with a significantly increased likelihood of EPE and positive surgical margin. This should be considered in the future studies dealing with prognostic value of TV and in studies assessing active surveillance criteria.

The Journal of urology. 2016 Jun 09 [Epub ahead of print]

Oleksandr N Kryvenko, Jonathan I Epstein

Department of Pathology and Laboratory Medicine, Department of Urology, and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL. Electronic address: ., Departments of Pathology, Urology, and Oncology, The Johns Hopkins Medical Institutions, Baltimore, MD.

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