[827] Atypical Small Acinar Proliferation, When Combined with Prostatic Intraepithelial Neoplasia on Biopsy, Has a Higher Rate of Cancer Detection on Subsequent Biopsies Than When Diagnosed Alone

JL Merrimen, G Jones, CS Leung, LR Kapusta, JR Srigley. McMaster University, Hamilton, Canada; Mount Sinai Hospital, Toronto, Canada; University of Toronto, Toronto, Canada

Background: Atypical small acinar proliferation (ASAP) can occur in three different situations in the prostatic needle biopsy (PNB): ASAP alone, or associated with high grade prostatic intraepithelial neoplasia (HPIN); either discontinuous (ASAP+PIN) or contiguous (PIN-ASAP). Using a large data set, we assess whether these different subgroups of ASAP denote a differing risk for detection of subsequent PCa.
Design: We reviewed the pathologic findings from 12304 men who underwent initial PNB during an 8 year period (May 1999- June 2007). PNBs were obtained from 28 community-based urologists in a setting without population based screening, typically for abnormalities in serum PSA or digital rectal examination. The PNBs were read by 3 urologic pathologists. Patients were included in the study if their initial diagnosis was ASAP, either alone or combined with HPIN, or a benign (BN) diagnosis and if at least one follow-up PNB was performed.
Results: Of the 12304 patients, 4938 (40.1%) and 329 (2.7%) had BN and ASAP diagnoses on initial biopsy. 1033 patients (845 BN; 189 ASG) were included in the study. The average number of PNBs was 2.3 and 2.4, the mean follow-up time was 2.4 and 1.2yr, and the time to second PNB was 2.1 and 0.7yr in the BN and ASAP groups, respectively. 187 (22%) and 91 (49%) developed PCa in the BN and ASAP groups, respectively (p<0.0005). These groups differed by age (61 vs 64yr, p<0.00005) but not by PSA, or extent of sampling (at first PNB). Only initial PSA predicted subsequent PCa detection (p=0.03, stratified by group). Within the ASAP group, Kaplan-Meier plots and Cox regression analyses reveal differing patterns in PCa detection. In all subgroups, there is a high rate of PCa detection within 0.7 yr, however, after this point the ASAP+PIN and PIN-ASAP subgroups separate from the ASAP alone subgroup and show a higher rate of PCa detection. This separation reaches statistical significance (p=0.05) at 3yr after initial PNB, at which point 45% of the ASAP alone patients are PCa free and only 29% of ASAP with HPIN patients are PCa free.
Conclusions: ASAP on initial PNB carries a high risk for subsequent detection of PCa compared to patients with a BN diagnosis. The presence of ASAP combined with HPIN, in any pattern, is associated with a greater risk of PCa detection in the long term (>3 yrs).
Category: Genitourinary (including renal tumors)

Tuesday, March 10, 2009 11:15 AM

Platform Session: Section A, Tuesday Morning