e15102 Background: TAS-102 is effective in refractory mCRC and significantly improved survival versus placebo. Currently no predictive biomarkers are established and used in clinical practice. Methods: We analyzed data of 160 patients treated with TAS-102 in real clinical practice in Czech Republic. Different factors associated with progression-free survival (PFS) and overall survival (OS) were evaluated. Results: Baseline patients’ characteristics: median age 66 years (range 28-83), 106 patients were male (66.3 %), ECOG PS 0 had 38.1 %, RAS wt 45 %. Anti-VEGF treatment had 83.1 %, anti-EGFR 43.8 %. Median number of TAS-102 treatment line was 3 (range, 2 – 8), median TAS-102 cycles 3 (range 1 – 27). At the time of analysis 15 % continued in treatment, 73.7 % discontinued due to progression, 6.9 % due to toxicity, 3.8 % decided to discontinue in treatment. Median PFS was 3.3 months (95% CI, 3.0 – 3.5), and median OS 10.2 months (95% CI, 8.9 – 11.8). Factors significantly associated with PFS and/or OS were: PS, time from diagnosis of mCRC, initiation of TAS-102 treatment > 3 months from last fluoropyrimidine, baseline CRP, WBC, neutrophils count, monocytes count, NLR, neutropenia ≥ G2, diarrhea ≥ G1, thrombocytopenia ≥ G2, required TAS-102 dose reduction and cycle delay. We developed a scoring system TAScore from factors at the beginning of treatment (PS 0, initiation of TAS-102 > 3 months from fluoropyrimidine, time from diagnosis of mCRC, baseline CRP, WBC, monocytes count < 0.5 × 109/L). For each factor patient received 1 point, the overall score was the sum of these points and patients were divided into 3 groups: high risk group with 0 to 1 point, intermediate with 2 to 3, favorable with 4 or more points. OS according to risk group was: 5.7 months for high risk (11 patients), 8.7 for intermediate (63), 12.8 for favorable (59) (P < 0.0001). TAScore was also associated with PFS: 2.4 months for high risk, 2.9 intermediate and 3.9 for favorable risk group (P < 0.0001). Conclusions: TAS-102 is effective in patients with refractory mCRC. We propose simple scoring system TAScore to help with precise patient selection at the beginning of TAS-102 treatment.