Comparison of contemporary methods for estimating prostate tumour volume in pathological specimens

To evaluate the accuracy of various prostate tumour volume (TV) estimation methods. To determine the most appropriate estimation method for current clinical practice.

Radical prostatectomy (RP) specimens from multiple institutions were analysed by a single uro-pathologist between September 2009 and May 2011. Tumour properties including thickness, width and length were collected and TV was established using computer-assisted image analysis (CAIA). TV estimation methods including; square, cuboidal and ellipsoidal estimations were calculated using previously reported formulae. The estimation methods were compared against the 'gold-standard' and the accuracy of identifying clinically significant tumours of TV ≥0.5 cc was determined.

In all, 299 consecutive specimens were analysed by a single uropathologist. The median index TV on CAIA was 1.42 cc. Of the four estimation methods, the ellipsoid methods produced the closest correlation with the gold-standard (r(2) 0.91, P = 0.71). This correlation lost accuracy when larger tumours (TV >4 cc) were excluded from the analysis (r(2) = 0.73, P = 0.003). Sensitivity and specificity for identifying clinically significant tumours was 94% and 92% respectively, when using the ellipsoid estimation.

In current uro-pathology, the ellipsoidal estimation method appears to be the most suitable for estimating TV in prostate cancers. This method is cheap, reproducible and sensitive and can be safely used as a surrogate for CAIA volumes when such technology is not available.