S68 Abstracts Poster Session, Saturday 28 January 2017 Table (abstract 481): 5-year OS estimates, with adjuvant chemotherapy when indicated (FOLFOX) Patient ONCOPRE Adjuvant! Mayo ACCENT Historical data Clinical trials 60 year-old male, stage 2 colon cancer Stage 2a: 87% Stage 2b: 83% Stage 2c: 57% Currently not available Stage 2 not supported Stage 2a: 85% Stage 2b: 72% Stage 2c: 37% 91% (all stage 2, with FOLFOX) and 3 75 year-old female, stage 3 colon cancer Stage 3a: 79% Stage 3b: 73% Stage 3c: 59% Currently not available Stage 3a: 88.8% Stage 3b: 67.0% Stage 3c: 63.3% Stage 3a b : 83% Stage 3b b : 64% Stage 3c b : 44% 80% (all stage 3, with FOLFOX, mean age 60) 40 year-old male, stage 2 colon cancer, MSI +ve Stage 2a a : 93% Stage 2b a : 78% Stage 2c: 57% a Currently not available Stage 2 not supported Not available for MSI +ve 88% (includes stage 2 and 3, without adjuvant chemotherapy) a Without adjuvant chemotherapy. b Mean age 60 years. It provides unique predictions dependent on the selected disease stage and adjuvant treatment regimen. Results demonstrate that our outcome estimates compare favorably with survival findings from landmark clinical trials and those from population-based settings. Further, our estimates are more optimistic and precise when compared to historical data and estimates generated by existing calculators (see table). Conclusions: ONCOPRE (www.oncopre.com/beta/) represents a new decision support tool that can assist in adjuvant therapy decision-making in colon cancer. Calculators must consider biomarkers as they improve capacity for prediction. Our platform serves as a potential model on which to develop prediction tools for other cancers. No conflict of interest. 482 POSTER Simultaneous, but not consecutive combination with folinate salts potentiates 5-fluorouracil antitumor activity in vitro A. Di Paolo 1 , P. Orlandi 1 , T. Di Desidero 1 , R. Danesi 1 , G. Bocci 1 . 1 Division of Pharmacology, Dept. Clinical and Experimental Medicine, Pisa, Italy Background: The combination of 5-fluorouracil (5-FU) and folinate salts has shown better clinical responses if compared to the fluoropyrimidine alone. However, the simultaneous 5-FU and calcium levofolinate (CaLV) mix and infusion is impossible due to drug precipitation. Therefore, a sequential administration of CaLV followed by 5-FU was adopted in the clinical routine. At the beginning of the 2000s, disodium levofolinate (NaLV) was available which can be easily administered simultaneously with 5-FU instead. The aim of this study was to investigate if there were pharmacological differences between the sequential administration of folinate salts (1 h before) followed by 5-FU and the simultaneous administration of both drugs in in vitro settings. Materials and Methods: Proliferation and apoptotic assays were performed on human colon cancer (HT-29, Caco-2) cell lines exposed to 5-FU, CaLV or NaLV, or their simultaneous and sequential combination for 24 and 72h, respectively. The synergistic, additive or antagonistic effects of the combinations were evaluated by the methods of Chou based on the combination index. Apoptosis was analyzed using the Cell Death Detection ELISA Plus Kit. Thymidylate synthase (TYMS) and reduced folate carrier (SLC19A1) gene expression was performed with real-time polymerase chain reaction and the quantification was obtained using the DDCt calculation. Results: As expected, the simultaneous combination of folinate salts and 5-FU was synergistic or additive in a 24 h treatment in both cell lines. In contrast, the sequential combination of both folinate salts (1 h before) and then 5-FU was surprisingly antagonistic in a 24 h treatment. Simultaneous NaLV+5-FU maintained its advantage, differently from CaLV+5-FU, even after 72h of treatment. The sequential combination of NaLV or CaLV followed by 5-FU confirmed to be antagonistic also at 72 h. Moreover, the simultaneous combination (but not the sequential one) of 5-FU and NaLV or CaLV significantly increased the percentages of apoptotic cells and the inhibition of TYMS gene expression after 24 h exposure. On the other side, the sequential combination (but not the simultaneous one) of 5-FU and CaLV or NaLV significantly inhibited the SLC19A1 gene expression after 24 h treatment. Conclusions: The simultaneous in vitro 24 h-treatment of 5-FU and both folinate salts formulations potentiated the antiproliferative effects of the drugs. This synergism was completely lost in the sequential combination at 24 h and 72 h of treatment. These preliminary in vitro findings seem to suggest that folinate salts are better given simultaneously in a single i.v. infusion line (i.e. NaLV) or with the aid of two separate ones (i.e. CaLV), rather than to anticipate their administration of 1 or 2 h for practical reasons. Conflict of interest: Corporate-sponsored Research: Unconditioned grant from Medac Pharma Italia to G.B. 483 POSTER CXCR4 promotes adhesion capacity and activates the AKT signalling pathway in colorectal cancer cells F. Zheng 1 , V. Flamini 2 , R. Bradbury 2 , Z. Zhang 1 , W.G. Jiang 2 , Y. Cui 2 . 1 Department of General Surgery- Beijing Key Laboratory of Cancer Invasion and Metastasis Research & National Clinical Research Centre for Digestive Diseases- Beijing Friendship Hospital, Capital Medical University, Beijing, China; 2 Cardiff University School of Medicine, CCMRC, Cardiff, United Kingdom Background: Colorectal cancer (CRC) is one of the most common cancers over the world. The major cause of CRC death is tumour metastasis to the liver and other organs. CXCR4 expression is positively associated with recurrence and poor survival of CRC patients. The axis of CXCR4/SDF-1 has been reported to show an important role in some cancer metastasis. The aim of study was to explore the role of CXCR4 in the adhesive capacity of CRC cells, which is essential for CRC metastasis. Materials and Methods: The technique of CRISPR/Cas9 genomic editing was used to knockdown CXCR4 on Colorectal cancer cell lines. Following electroporation of the sequence-verified CRISPR plasmids, the knockdown of CXCR4 was validated using T7EN1, FACS and Western Blotting, respectively. Cell proliferation was analysed using Alamar Blue assay following treatment. CRC cell adhesion to HUVEC cells was accessed by using DiO cell-labelling solution. CRC cell adhesion to Matrigel was determined using the Crystal violet assay. Cell migration and invasion were evaluated using transwell insert assays with or without Matrigel coating. The Electric Cell-Substrate Impedance Sensing (ECIS) system was also used to monitor cell behaviours. Results: Knockdown CXCR4 slightly increased proliferation of HT115 CRC cells with time dependence until cells reached confluency. This knockdown however decreased the adhesion of cancer cells to HUVEC endothelial cells and Matrigel, respectively. The decrease of adhesion capacity was also confirmed by using the ECIS (Electric Cell-Substrate Impedance Sensing) system. The CRISPR-mediated CXCR4 knockdown reduced the level of total and phosphorylated AKT (ser473) proteins. The upregulation of ERK, MEK and IGF1R genes by CXCR4 knockdown was eliminated in the presence of stromal development factor 1 (SDF1), the CXCR4 ligand. Conclusions: CXCR4 plays a role in promoting adhesion capacity of CRC cells, probably via activation of the inaction of AKT signalling pathway. SDF-1 is able to eliminate the upregulation of ERK, MEK and IGF1R genes by CXCR4 knockdown, suggesting that the level of SDF-1 in tumour microenvironment is very crucial for the function of CXCR4. No conflict of interest. 484 POSTER DISCUSSION Evaluation of guideline adherence in colorectal cancer treatment in The Netherlands: a survey among medical oncologists by the Dutch Colorectal Cancer Group (DCCG) L. Keikes 1 , M. Van Oijen 1 , V. Lemmens 2 , M. Koopman 3 , C. Punt 1 . 1 Academic Medical Center, Medical oncology, Amsterdam, Netherlands; 2 Comprehensive Cancer Organisation IKNL, Research, Eindhoven, Netherlands; 3 University Medical Center Utrecht, Medical oncology, Utrecht, Netherlands Background: Clinical guidelines are generated to preserve high quality evidence-based care. In 2014, several adjustments for the systemic treatment in the adjuvant and metastatic setting were introduced in the Dutch colorectal cancer guidelines. Data on the implementation of guidelines into clinical practice are scarce, despite the fact that guideline adherence is known to prevent over- and undertreatment and is related to survival. Therefore, the aim of this survey is to investigate adherence to the Dutch guidelines for the systemic treatment in high risk stage II and stage III colon cancer and metastatic colorectal cancer.