[1007] Re-Biopsies Are Not Necessary for Isolated High-Grade PIN

M Varma, ProtecT Histopathology Group. University Hospital of Wales, Cardiff, United Kingdom

Background: The reported high frequency of prostate cancer on re-biopsy for isolated high-grade PIN (HGPIN) may be at least partly due to case selection, as in most studies only a relatively small proportion of these patients (presumably many with other risk factors) underwent re-biopsy. Non-targeted systematic prostate biopsy detects only a proportion of cancers in the prostate so even routine re-biopsy of patients with elevated PSA and negative first biopsy would be positive in a small but significant proportion of cases.
Design: We report our experience in a PSA screening multi-centre study in which at least 10 cores were obtained from each patient (initial biopsy and re-biopsy) and all patients with HGPIN detected on initial biopsy were recommended re-biopsy. The frequency of cancer found on re-biopsy for HGPIN (<18mths from first biopsy) was compared with the estimated “background re-biopsy cancer rate” (predicted cancer rate on re-biopsy of all patients with negative first biopsy) calculated using the formula: Background re-biopsy cancer rate = a*(1-b)/(1-a) where (a) is the observed first biopsy cancer rate in the population expressed as a fraction; and (b) is the putative cancer detection fraction (ie. fraction of cancers in the prostate detected by the biopsy procedure).
Results: Of 5305 patients from 6 centres who underwent prostate biopsy, cancer was found in 1806 (34%) and isolated HGPIN in 493 (9.3%) of first biopsies. 392 (79.5%) cases of isolated HGPIN underwent re-biopsy. The outcome of re-biopsy (Table 1) was compared with the estimated background re-biopsy cancer rate at various putative cancer detection fractions (Table 2).

Table 1

	No. of cases	Cancer on re-biopsy
Focal HGPIN (<4 cores)	351 (89.5%)	39 (11.1%)
Widespread HGPIN (>3 cores)	41 (10.5%)	6 (14.6%)
TOTAL	392 (100%)	45 (11.5%)

Table 2

Putative cancer fraction	0.7	0.75	0.8	0.85	0.9
Estimated Background Re-biopsy Cancer Rate (%)	15.5	12.9	10.3	7.7	5.2

Even at an improbably high cancer pick-up fraction of 0.9 (ie. 90% of cancers present are detected by biopsy) the rate of cancer following re-biopsy for focal (<4 cores) HGPIN was only 5.9% above the background cancer rate. The number of cases of widespread (>3 cores) HGPIN were too few for proper analysis but the cancer rate on re-biopsy was only 14.6%.
Conclusions: Re-biopsy is not necessary for isolated HGPIN in the absence of other risk factors.
Category: Genitourinary (including renal tumors)

Monday, March 22, 2010 8:45 AM

Platform Session: Section A, Monday Morning