Chromosomal instability and chromothripsis as a prognostic factor for metastatic colorectal cancer Elina Skuja, Dagnija Kalniete, Miki Nakazawa-Miklasevica, Zanda Daneberga, Arnis Abolins, Gunta Purkalne, Edvins Miklasevics Pauls Stradins Clinical University Hospital, Riga, Latvia Riga Stradins University, Riga, Latvia Pauls Stradins Clinical University Hospital Background Materials and Methods In 10 tumor samples (52.6%) we found multiple chromosomal fragmentations (>100 breakpoints detected at one chromosome) – chromothripsis. The most affected chromosomes were chromosome 1, chromosome 2 and chromosome 6 (52.6% of patient). The maximal count of chromosomes affected with chromothripsis in one tumor sample was 20; this was seen in one patient. Survival data. Progression free survival (PFS) and overall survival were measured for all patients in study. The patient had 3 to 48 months of follow up. We observe: slight correlation between high BPI and longer PFS. mPFS for BPI ≥1400 was 14 months, mPFS for <1400 was 8 months (95%CI 1.07-10.99, p=0.03). Chromothripsis was associated with better survival. mPFS in patient with chromothripsis was 14 months, but in patient without detectable chromothripsis – 8 months ( HR 3.92, 95%CI 1.23-12.53, p=0.02). We didn't observe statistically significant impact of any clinical or biological factor on overall survival in our study, which could be explained with small patient number and different second and third line chemotherapy and selvage treatment strategies. Impacts of chromosomal rearrangements, mutations on pathogenesis, prognosis and treatment resistance, are widely described in metastatic colorectal cancer. Chromothripsis is massive chromosome fragmentation occurred in one catastrophic cell crisis observed in 2-3% cancer samples (1). Such genomic rearrangements can drive the development of cancer through several mechanisms including deletion of tumor suppressor genes and increased copy number of oncogenes. Chromothripsis has been associated with poor patient survival in several cancers (2,3), indicating it’s potential relevance as a prognostic marker, and suggesting chromothripsis as a feature of some particularly aggressive forms of cancer. Chromothripsis incidence and impact on survival in colorectal cancer is unclear, but this could be prevalent genomic rearrangement (4). DNA was extracted from the formalin-fixed paraffin-embedded (FFPE) samples with QIAamp DNA Mini Kit (Qiagen) according to the instruction of the manufacturer. DNA quality was evaluated with Illumina FFPE QC Kit (Illumina) using RT-PCR. DNA was restored using Illumina DNA restoration Kit (Illumina). Microarray analysis was performed using Infinium HumanOmniExpress-12 v1.0 FFPE BeadChip Kit. BeadChip was imagen on HiScan (Illumina). Data was visualized and analyzed by GenomeStudio (Illumina) software.  Analyses were performed using R version 3.1.2. Copy number variation and break points on the chromosomes were analyzed by using "DNAcopy" package. Overall survival and progression free survival rates were estimated using the Kaplan-Meier method. The log-rank test was used to calculate any significant difference between the subgroups by univariate analysis. Significance levels were set at p< 0.05. All statistical analyses were performed by using MedCalc. Results The highest number of breakpoint was seen in chromosome 1 (27-365 breakpoints), followed by chromosome 2 (25-315), suggesting importance of these chromosomes in colorectal cancer genesis. The lowest density of breaks occurred at chromosome 21 (7-99breakpoints). Total number of breakpoints per genome in cancer sample – breakpoint instability index (BPI) – was 368-4009. Conclusion In our study, we found a correlation between DNA massive fragmentation – chromothripsis and PFS in metastatic colorectal cancer. As opposed recent studies suggested chromothripsis associated with worse prognosis, we find chromothripsis as positive predictive factor to chemotherapy. Chromothripsis and breakpoint instability index per se did not show better OS in all cases, we suggest it is one of multiple factors predicting treatment response and prognosis. Age 63.15 (38-78) Gender: Male Female   11 (57.89%) 8 (42.11%) Tumor localization: Left part – sigmoid colon cancer, rectal cancer Right part - Colon cancer Grade: Unknown G2 G3 1 (5.26%) 13 (68.42%) 5 (26.32%) Metastases: Synchronous Metachronous Median time to metastases 12.25 moths (9-18) Stage II – 3 patients Stage III – 1 patient 15 (78.95%) 4 (21.05%) Liver only other 10(52.63%) 9(47.37%) KRAS status in primary tumor: Wild type Mutation in 12 codon Mutation in 13 codon Not known 10 (52.64%) 7 (36.84%) Serum CEA before chemotherapy: CEA ≤5.5 ng/ml CEA >5.5 ng/ml Level of CEA, ng/ml 12 (63.16%) 232.1 (7.1 – 959.8) Median follow up (months) 25.5 (3 – 48) mPFS 1year PFS 2 year PFS 8 months 33.3% 5.6% mOS 1 year OS 2 year OS 3 yearOS 21months 78.9% 42.1% 21.1% Materials and methods 19 metastatic colorectal cancer patients who received FOLFOX type first line chemotherapy in Clinic of Oncology of Pauls Stradins Clinical University Hospital in Latvia in 2011 – 2012 where selected for this study. The study was performed with approval from the ethics committee of Riga Stradin’s University Written informed consent was taken from each patient who underwent study. Tissue samples were previously acquired as part of series of routine diagnostic and pathological analyses in our hospital. Acknowledgements References: Stephens PJ, Greenman CD, Fu B, et al. Massive Genomic Rearrangement Acquired in a Single Catastrophic Event during Cancer Development. Cell. 2011;144(1):27-40. Magrangeas F, Avet-Loiseau H, Munshi NC, Minvielle S. Chromothripsis identifies a rare and aggressive entity among newly diagnosed multiple myeloma patients. Blood. 2011;118(3):675-678. Rausch T, Jones DTW, Zapatka M, et al. Genome Sequencing of Pediatric Medulloblastoma Links Catastrophic DNA Rearrangements with TP53Mutations. Cell. 2012;148(1-2):59-71. Kloosterman WP, Hoogstraat M, Paling O, et al. Chromothripsis is a common mechanism driving genomic rearrangements in primary and metastatic colorectal cancer. Genome Biology. 2011;12(10):R103. . Your text would go here. Your text would go here.