MP35-06 ESTABLISHMENT OF A FISH BASED ANALYSIS FOR INDIVIDUAL RISK ASSESSMENT OF CCRCC PATIENTS ON TISSUE MICRO ARRAYS

Abstract

INTRODUCTION AND OBJECTIVES: ArrayCGH and FISH analysis revealed a significant correlation between aberrations in critical chromosomal regions, metastatic risk and cancer specific survival. Based on these copy number variations (CNVs) a total number of specific aberrations score system (TNSA score) was established that appears to be promising as prognostic test for individual risk assessment of ccRCC patients who underwent partial or radical nephrectomy. The aim of this ongoing study was to verify the prognostic value of the 4 most promising aberrations in an independent cohort and to establish the technique on formalin fixed paraffin embedded tissue for tissue micro array (TMA) processing in order to develop a prognostic FISH assay in the future. Furthermore the expression of tumor associated genes located in the examined regions is to be performed to offer valuable clues to further the understanding of the metastatic process. METHODS: FISH experiments were performed on isolated cell nuclei from 31 ccRCCs (18metastasized/13 non-metastasized) and 48 FFPE sections on TMAs of a different cohort (9 metastasized/39 nonmetastasized). For each critical chromosomal region (1q21.3, 7q36.3, 9p21.3p24.1 und 20q11.21q13.32) commercially available FISH probes were used and the best cut-off values for prediction of metastatic risk were determined by ROC-curve analysis. The total number of specific aberrations (TNSA) was calculated for each tumor based on the dichotomized specific genomic alterations. RESULTS: Loss of 9p21.3p24.1, TNSA, gain of 7q36.3 and Tcategory were significantly associated with metastasis in the Homburg cohort. Of the examined chromosomal regions loss of 9p21.3p24.1 was the best predictor of metastasis (AUC1⁄40.795, p-value1⁄40,002) followed by TNSA (AUC1⁄40.795, p-value1⁄40,027) compared to aberrations of the other loci (AUC: 0.607-0.701). FISH analysis on FFPE samples of TMAs of an independent cohort showed similar results for 9p21.3p24.1 (AUC1⁄40.739, p-value1⁄40.003) for the prediction of metastatic risk. In this cohort loss of 9p21.3p24.1 was the only statistically relevant predictor of metastasis compared to common prognostic factors such as T-stage, grade and tumor-size. CONCLUSIONS: We could validate TNSA as well as loss of 9p21.3p24.1 as prognostic factors for metastatic risk. Interphase FISH proves to be a dependable method for prognostic evaluation in primary tumor tissue on isolated cell nuclei as well as on FFPE sections. As this is an ongoing study the reliability of the score has to be verified for the whole cohort.