MP51-04: P-score in preoperative biopsies accurately predicts P-score in final pathology at radical prostatectomy

Pontus Röbeck*, Uppsala, Sweden, Li-Di Xu, Dilruba Ahmed, Stockholm, Sweden, Anca Dragomir, Pär Dahlman, Sam Ladjevardi, Michael Häggman, Uppsala, Sweden

Introduction: Prostatype RT-qPCR kit analyses the expression of 3 genes (IGFBP3, F3, and VGLL3) in formalin-fixed paraffin-embedded prostate cancer (PCa) tissues. The gene parameter is combined with patient-specific clinical parameters in a pre-defined algorithm to calculate the P-score, which has previously been shown to improve prediction performance of PCa-specific death as compared to clinical parameters only. 

To establish the prognostic accuracy of P-score in MRI/TRUS fusion-guided diagnostic biopsies as compared to P-score in the paired radical prostatectomy specimens and to elucidate the concordance of P-score in the paired index- and concomitant non-index tumour foci.

Methods: 98 men with localized PCa, all diagnosed by MRI/TRUS fusion-guided biopsies, underwent robot-assisted radical prostatectomy. All prostatectomies were whole-mounted and tumour maps were drawn. From all biopsies and from index and non-index tumour foci of the corresponding prostatectomies, gene expression was assessed with Prostatype and P-score was computed. This P-score was calculated in a range of 0-15 with one as the smallest unit and categorised into three risk groups by using previously defined cut-offs.

Results: Preoperative biopsies yielded sufficient and technically analysable materials for comparison with the prostatectomy in 71 men. Biopsy P-score significantly correlated with P-score in corresponding prostatectomy with a Pearson correlation of 0.84 (95% CI: 0.75-0.89, p<0.0001). P-score in paired biopsy and prostatectomy were also in substantial agreement (weighted kappa score 0.68). P-score in index tumour significantly correlated with P-score in the paired concomitant foci (Pearson correlation: 0.83, 95% CI: 0.74-0.90, p<0.0001). P-score in the paired index tumour and the concomitant foci were also in agreement (weighted kappa score: 0.68).

Conclusions: P-score in preoperative fusion-guided biopsies accurately predicts the P-score in the prostatectomy. P-score in index tumour and concomitant foci also show substantial concordance. Thus, biopsy P-score is adequate for assisting with predicting prostate cancer progression.

Source of Funding: Uppsala University Hospital