565PA BAR CODE OF SELECTED GENE COPY NUMBER ALTERATIONS IS ASSOCIATED WITH DISEASE-FREE SURVIVAL IN STAGE II-III MICROSATELLITE STABLE (MSS) COLON CANCER

ABSTRACT Aim: Genomic quantitative alteration is a backbone event during the carcinogenesis process in microsatellite stable colon cancer. However, the prognostic value of loss or gain of the main genomic regions is still controversial. We conducted a prospective study to assess the prognostic impact of the main genomic quantitative alterations in stage II-III MSS colon cancer (NCT02110329). Methods: Patients treated for stage II-III colon cancer from 01/2002 to 01/2009 with available frozen tissue were included. The Quantitative Multiplex PCR of Short Fluorescent Fragments (QMPSF) method was used for molecular screening (1). The QMPSF was based on the simultaneous amplification, from normal and tumoral tissues, of 8 selected target genomic sequences according to literature data: DCC (18q21); EGFR (7p12); TP53 (17p13.1); BLK (8p23-p22); MYC (8q24.12); APC (5q22.2); ERBB2 (17q12); STK6 (20q13.31); and two control: PCBD2 (5q31.1); HMBS (11q23.3). The primary end-point was to determine the association between molecular alterations and disease-free survival (DSF). Combinations of alterations were defined according to univariate results (p Results: A total of 401 patients were included with a median follow-up of 48 months. There were 236 stage II and 165 stage III and the recurrence rate was 30.2%. Loss of DCC/18q, TP53/17p, BLK/8p, and APC/5q were detected in respectively 33.2%, 26.7%, 22.7%, 9.7% and gain of EGFR/7p, MYC/8q, ERBB2/17q and STK6/20q were observed in 31.7%, 35.7%, 18.7% and 48.9% of cases, respectively. There was no significant interaction between alterations and disease stage. DFS was significantly associated with loss of DCC/18q (57.5 vs 70.6%, p = 0.02) with a trend for BLK/8p loss (59.8 vs 68.6%, p = 0.08) and ERBB2/17q gain (59.2 vs 68.5%, p = 0.14). In multivariate analysis, the combination of loss DCC/18q and/or loss BLK/8p and/or gain ERBB2/17q was significantly associated with DFS. The DFS significantly decreased from 74.2% to 61.7% (HR = 1.78, 95CI: 1.14-2.77) and to 57.2% (HR =2.06, 95CI: 1.26-3.37) in patients with respectively none, 1 and at least 2 of these 3 alterations. Conclusions: Combination of DCC/18q, BLK/8p and ERBB2/17q gene copy number alterations is associated with disease-free survival in stage II-III colon cancer. Disclosure: All authors have declared no conflicts of interest.