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).
|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%)|
|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|