The ratio of prostate chips with cancer: a new measure of tumor extent and its relationship to grade and prognosis.

The ratio of chips with cancer to the total number of chips was studied in 118 patients with prostate cancer who underwent transurethral prostatectomy. We found that this ratio is a prognosticator closely associated to the stage of tumor (local or extensive) and to the chance of death from prostate cancer. Stage, the ratio of positive chips and the Gleason histologic score are all closely tied one to another, and it is unclear from this initial study whether these variables provide independent or additive prognostic information. Nevertheless, the ratio of positive chips shows far better interobserver agreement than does the Gleason score, and in patients with the most common predominant score of three, it can separate most of those with localized disease from most of those with extensive disease. Thus the ratio shows promise as a reliable predictor of stage of disease and of long-term failure, and hence it may help in the choice of patients for curative surgery.