Clinical significance of alterations of chromosome 8 detected by fluorescence in situ hybridization analysis in pathologic organ‐confined prostate cancer

Abstract

Loss of 8p22 and gain of 8q24 are known to be common chromosomal alterations in prostate cancer. We have previously demonstrated that concurrent 8q24 overrepresentation and 8p22 loss were associated with a poor prognosis in patients with high-grade, locally advanced prostate cancer. We evaluated the alteration of 8p22 and 8q24 in a large cohort of pathologic organ-confined prostate cancer using fluorescence in situ hybridization (FISH) analysis. All 195 patients with Gleason scores > 5, pathologic stage T₂N₀M₀ (pT₂N₀M₀) prostate cancer, who underwent a radical prostatectomy at the Mayo Clinic between 1987 and 1991, and for whom blocks were available, were selected for this study. The median follow-up period was 9.5 years, and endpoints of this study were biochemical and clinical disease progression. The latter includes local as well as systemic disease progression. FISH analysis using paraffin-embedded tissues was performed for 8p22 (LPL), centromere 8 (8cen), and 8q24 (MYC) and was successful for 156 tumors (80.0%). Of these tumors, 104 (66.6%) had one or more numeric alterations of the 3 loci evaluated. An increased copy number of 8q24 was observed in 66 (42.3%) tumors, of which 20 (12.8%) had an additional increase (AI) of 8q24, and 46 (29.5%) had a gain of 8q24 with an equivalent gain of 8cen. Losses and gains of 8p22 were detected in 81 (51.9%) and 20 (12.8%) tumors, respectively. An AI of 8q24 was significantly associated with the tumor Gleason score (P = 0.042). Univariate analysis indicated that loss of 8p22 was a significant predictor of biochemical and clinical disease progression (P = 0.025 and P = 0.011, respectively). Furthermore, the group with loss of 8p22 concurrent with an AI of 8q24 (Loss 8p22-any 8cen-AI 8q24) had an increased rate of biochemical disease progression (P = 0.052). Multivariate analysis demonstrated that neither individual nor the Loss-any-AI combination of alterations was a significant independent predictor of disease progression when adjusting for Gleason score, preoperative PSA levels, and DNA ploidy. These data suggest that loss of 8p22 is associated with a poor prognosis, specifically when it is accompanied by AI of 8q24 in pT₂N₀M₀ prostate cancer.