There were 16 responders and 23 non-responders. By multivariate logistic regression analysis, high OPRT/TS (>1.246 vs. ≤1.246, odds ratio (OR) 16.962, 95% CI 1.781–161.581, P = 0.014) and peritoneal metastasis (vs. liver metastasis, OR 25.604 (1.852–353.979), P = 0.016) were independently predictive of responding. OPRT/TS differed between responders and non-responders (median ± SD 1.442 ± 0.091 vs. 1.158 ± 0.133, P = 0.037) and response rates differed between patients with high OPRT/TS and low OPRT/TS (>1.246 vs. ≤1.246, 57.1 vs. 22.2%, P = 0.040). Figure 2a shows the ROC curve of OPRT/TS for predicting response.Fig. 2 a ROC curve of OPRT/TS for predicting response and b the ROC curve of OPRT/DPD for predicting grade 3–4 AEs. ROC receiver operating characteristic, OPRT orotate phosphoribosyltransferase, TS thymidylate synthase, DPD dihydropyrimidine dehydrogenase, AEs adverse events