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Purpose Preoperative chemotherapy for colorectal liver metastases (CLM) can produce histologic changes in the nontumor-bearing liver (NTBL) that may impact on surgical outcomes. Patients and Methods From a cohort of 303 patients treated for CLM with liver resection, 92 patients (75 received preoperative chemotherapy: group C+; and 17 were chemotherapy naïve: group C−) were randomly selected for detailed pathologic analysis. Preoperative chemotherapy consisted of fluorouracil (FU)/leucovorin alone (23 patients, the majority chronomodulated) or in combination with oxaliplatin (52 patients, all chronomodulated). To determine associations between study factors, clinical and operative variables were compared with pathology data and surgical outcomes. Results Although clinical and operative factors were similarly distributed, C+ patients, compared with C− patients, were more likely to receive intraoperative RBC transfusions (mean units: 1.9 v 0.5, respectively; P = .03) and to have vascular abnormalities in the NTBL (52% v 18%, respectively; P = .01). Presence of the most severe forms of vascular alterations was closely associated with RBC transfusion requirements (P = .04). In contrast, moderate to severe steatosis was similarly distributed (C− group, 12%; C+ group, 13%). Although perioperative mortality and morbidity rates were similar in all groups, more than 12 courses of chemotherapy, compared with ≤ 12 courses, predisposed patients to reoperation (11% v 0%, respectively; P = .04) and to longer hospitalization (15 v 11 days, respectively; P = .02). Conclusion The main hepatic lesion induced by preoperative FU/oxaliplatin chemotherapy in patients with CLM is vascular and not steatosis. Detailed pathologic analysis determined that the most severe vascular lesions are associated with increased intraoperative transfusions. The risk for other postoperative complications is related to the duration of preoperative chemotherapy administration.

4079 Background: Microvascular invasion (MVI) is the strongest prognostic factor following surgery of hepatocellular carcinoma (HCC). However, it is usually not available on the preoperative setting. A predictive model of MVI in patients scheduled for hepatic resection (HR) or liver transplantation (LT) would thus help guiding treatment strategy. The aim of this study was to develop a predictive model for MVI of HCC before either HR or LT. Methods: HCC patients who consecutively performed HR or LT from January 1994 to June 2016 at a single institution were subdivided into a training and validation cohort. Risk factors for MVI in the training cohort were used to develop a predictive model for MVI, to be validated in the validation cohort. The outcomes of the HR and LT patients with high or low MVI probability based on the model, were compared using propensity score matching (PSM). Cut-off values for continuous factors were determined based on ROC curve analysis. Results: A total of 910 patients (425 HR, 485 LT) were included in the training (n = 637) and validation (n = 273) cohorts. In the training cohort, multivariate analysis demonstrated that alpha-fetoprotein ≥100ng/ml ( p < 0.0001), largest tumor size ≥40mm ( p = 0.0002), non-boundary HCC type on contrast-enhanced CT ( p = 0.001), neutrophils-to-lymphocytes ratio ≥3.2 ( p = 0.002), aspartate aminotransferase ≥62U/l ( p = 0.02) were independently associated with MVI. Combinations of these 5 factors varied the MVI probability from 15.5% to 91.1%. This predictive model achieved a good c-index of 0.76 in the validation cohort. In PSM (109 HR, 109 LT), there was no difference in survival between HR and LT patients among the high MVI probability (≥50%) patients, (5y-OS; 46.3% vs 42.2%, p = 0.77, 5y-RFS; 54.0% vs 28.8%, p = 0.21). Among the low probability ( < 50%), survival was significantly decreased following HR compared with LT (5y-OS; 54.1% vs 78.8%, p = 0.007, 5y-RFS; 17.3% vs 86.1%, p< 0.0001). Conclusions: This model developed from preoperative data allows reliable prediction of MVI, and may thus help with preoperative decisions about the suitability of HR or LT in patients with HCC.

3579 Background: Increasingly efficient chemotherapy regimens have improved the outcomes after R1 resection (tumor-free margin < 1 mm) for colorectal liver metastases (CLM). However the long-term s...

3529 Background: Preoperative chemotherapy for CRLM can produce histologic changes in non tumoral liver. Methods: A retrospective analysis was performed in data from 92 patients (pts) who had liver...