Absence of TMPRSS2:ERG fusions and PTEN losses in prostate cancer is associated with a favorable outcome

TMPRSS2:ERG gene fusions and PTEN deletions are the most common genomic aberrations in prostate cancer. Recent work has suggested that the TMPRSS2: ERG fusion is associated with a more aggressive phenotype. Similarly, PTEN deletion has been associated with biochemical recurrence and lymph node metastasis. To date, there has been no systematic analysis of the combined influence of genomic PTEN deletion with TMPRSS2: ERG gene fusions on clinical parameters of prostate cancer progression. We carried out a retrospective analysis of 125 prostate cancers with known clinical outcome using interphase fluorescence in situ hybridization to detect the relative prevalence of TMPRSS2: ERG rearrangements and/or PTEN genomic deletions. TMPRSS2: ERG rearrangement was found in 60 of 125 (48%) prostate cancers. Duplication of TMPRSS2: ERG fusion was observed in seven (6%) tumors. Gleason grade (P = 0.0002)/score (P = 0.001), median tumor volume (P = 0.0024), preoperative PSA (P = 0.001) and perineural invasion (P = 0.0304) were significantly associated with biochemical recurrence by univariate analysis with TMPRSS2: ERG approaching significance (P = 0.0523). By multivariate analysis, relevant factors associated with recurrence were Gleason scores 7 (P = 0.001) and 8-10 (P = 0.015), PTEN homozygous deletion (P = 0.013) and concurrent TMPRSS2: ERG fusion and PTEN deletion (P = 0.036). Kaplan-Meier analysis indicated that the presence of TMPRSS2: ERG fusion was marginally less favorable in comparison to no fusion. Duplication of fusion gene showed worse prognosis. It was possible to determine the relative frequencies of PTEN deletion and/or TMPRSS2: ERG fusions in 82 of 125 prostate cancers. With biochemical recurrence as an endpoint, the genomic biomarkers identified three patient groups: (1) 'poor genomic grade' characterized by both PTEN deletion and TMPRSS2: ERG fusions (23/82, 28%); (2) 'intermediate genomic grade' with either PTEN deletion or TMPRSS2: ERG fusion (35/82, 43%) and (3) 'favorable genomic grade' in which neither rearrangement was present (24/82, 29%). Kaplan-Meier and multivariate analysis indicate that TMPRSS2: ERG fusion and PTEN loss together are a predictor of earlier biochemical recurrence of disease.