Neoadjuvant chemoradiotherapy (CRT) followed by total mesorectal excision has emerged as the standard treatment for locally advanced rectal cancer (LARC) patients. However, many cases do not respond to neoadjuvant CRT, suffering unnecessary toxicities and surgery delays. Thus, identification of predictive biomarkers for neoadjuvant CRT is a current clinical need. In the present study, microRNA-31 expression was measured in formalin-fixed paraffin-embedded (FFPE) biopsies from 78 patients diagnosed with LARC who were treated with neoadjuvant CRT. Then, the obtained results were correlated with clinical and pathological characteristics and outcome. High microRNA-31 (miR-31) levels were found overexpressed in 34.2% of cases. Its overexpression significantly predicted poor pathological response (p = 0.018) and worse overall survival (OS) (p = 0.008). The odds ratio for no pathological response among patients with miR-31 overexpression was 0.18 (Confidence Interval = 0.06 to 0.57; p = 0.003). Multivariate analysis corroborated the clinical impact of miR-31 in determining pathological response to neoadjuvant CRT as well as OS. Altogether, miR-31 quantification emerges as a novel valuable clinical tool to predict both pathological response and outcome in LARC patients.

SET nuclear proto-oncogene (SET) deregulation is a novel molecular target in metastatic colorectal cancer (CRC). However, its role in CRC progression and its potential clinical impact in early-stage CRC patients remain unknown. Here, we studied the biological effects of SET on migration using wound-healing and transwell assays, and anchorage-independent cell growth using soft agar colony formation assays after ectopic SET modulation. SET was analyzed by immuno-staining in 231 early-stage CRC patients, and miR-199b expression was quantified by real-time PCR in a set of CRC patients. Interestingly, SET enhances cell migration, markedly affects the colony-forming ability, promotes epithelial to mesenchymal transition, and induces the expression of the MYC proto-oncogene (c-MYC) in CRC cells. SET overexpression was detected in 15.4% of cases and was associated with worse Eastern Cooperative Oncology Group (ECOG) status (p = 0.021) and relapse in stage-II CRC patients (p = 0.008). Moreover, SET overexpression predicted shorter overall survival (p < 0.001) and time to metastasis (p < 0.001), and its prognostic value was particularly evident in elderly patients. MiR-199b downregulation was identified as a molecular mechanism to deregulate SET in patients with localized disease. In conclusion, SET overexpression is a common alteration in early-stage CRC, playing an oncogenic role associated with progression and aggressiveness, and portends a poor outcome. Thus, SET emerges as a novel potential molecular target with clinical impact in early-stage in CRC.

Peritoneal metastases from gastric cancer play a key role in the fatal prognosis of the disease. The lack of efficacy of actual therapeutic approaches together with the outcomes achieved with checkpoint inhibitors in gastric cancer compel us to address the current state-of-the-art immunotherapy treatment of peritoneal dissemination. The immunogenicity of the peritoneum has been described to be particularly active at omentum and peritoneal lymph nodes. Also, both innate and acquired immunity seems to be involved at different molecular levels. Recent works show PDL1 expression being less present at the peritoneal level; however, some clinical trials have begun to yield results. For example, the ATTRACTION-2 trial has demonstrated the activity of Nivolumab in heavily pretreated patients even though peritoneal metastases were diagnosed in a 30% of them. Despite positive results in the metastatic setting, peritoneal responses to systemic checkpoint inhibitors remains unclear, therefore, new strategies for intraperitoneal immunotherapy are being proposed for different ongoing clinical trials.

E12007 Background: Breast cancer prognosis is influenced by several factors including Ki67 expression which may have a predictive role in luminal breast cancer patients. The aim of this study was to assess the value of Ki67 in breast cancers with positive hormonal receptors and HER2 overexpressed and to evaluate its impact on survival. Methods: Seventy eight consecutive patients diagnosed with locally advanced HER2 positive breast cancer who were treated with adjuvant therapy based on HER2 treatment were selected for this study (2004-2014). The adjuvant chemotherapy schemes were 44% TCH, 16% FEC, 11% AC/T and 29% other therapies. The median of followup was 68 months. Tumor proliferation was assessed immunohistochemically by Ki67 expression and calculated as percentage of stained tumor cells from this cohort previous to adjuvant chemotherapy administration and the results obtained were correlated with disease status and outcome. Results: High proliferation defined as a percentage > 15 of tumor cells was observed in 69% of the breast cancer patients cases. High proliferation significantly predicted longer overall survival (OS) (Log rank 0,012). At 10 years of follow-up, 93% of the patients with KI67 high expression were alive versus 43% of patients without overexpression. Multivariate analysis confirmed the clinical significance of Ki67 predicting OS for luminal HER2 breast cancer patients (p 0,04 y HR 9,6). Conclusions: High proliferation identifies a setting of luminal-B HER2+ subtype breast cancer patients with a significantly longer overall survival.

E12118 Background: The prognostic value of Ki67 in triple negative breast cancer (TNBC) is yet unclear because the cut-off points employed differ widely and its predictive effect may vary according to age. The purpose of this study was to analyze the role of Ki-67 among patients with TNBC, and determined the optimal Ki-67 cut-off point to demonstrate its prognostic relevance associated with patient age and treatment strategy. Methods: 201 patients treated for primary TNBC from 1999 to 2014 were identified from the breast surgery database. Clinicopathologic characteristics and outcomes were compared between patients treated with neoadjuvant or adjuvant chemotherapy. We used time-dependent receiver operating characteristic (ROC) curve and time-dependent area under the ROC curve (AUC) to evaluate the discriminative ability of Ki-67 at 3 and 5 years of follow up. A Ki-67 cut-off point was set up to maximize sensitivity and specificity. Interaction effect between age and Ki-67 on disease-free survival (DFS) and overall survival (OS) was evaluated by stratified analysis. Results: There was a non-significant Ki-67 cut off value to predict OS and DFS at 3 and 5 years neither in the whole serie (201) nor in the adjuvant group (125), and only a slightly better threshold for DFS in the neoadjuvant one (N = 46) at 5 years (AUC = 0.697). According to the coordinates of the ROC curves, the best cut-off point for Ki-67 was 60%. In the multivariate analysis (COX proportional hazards regression), high Ki-67 ( > 60%), was a poor prognostic factor for DFS in patients > 40 yo. Among the patients < 40 yo, high Ki-67 was a better prognosis factor. Conclusions: Our data suggest that a threshold of Ki-67 of 60% could provide a usefull tool to define patients with significantly different outcome in TNBC.

E15556 Background: It has been recently reported that miR-148a promotes hepatocytic differentiation and its expression levels correlates with hepatocytic markers such as the hepatocyte-specific miR-122. Moreover, miR-148a is downregulated in hepatocarcinoma cells and its restoration impaires tumor growth, reduces liver fibrosis and induces an increased hepatic differentiated phenotype in vivo. The liver represents the most common metastatic niche in colorectal (CRC) and based on these novel findings we hypothesized that miR-148a could be playing a relevant role in the establishment of liver metastasis. Although little is known about the significance of miR-148a in CRC, some data in the literature would suggest its tumor suppressor role. Methods: We analyzed miR-148a in an initial set of 17 CRC patients with paired primary and metastatic tissues. To measure miR expression levels in tumor samples we performed real‐time RT‐PCR on formalin‐fixed paraffin‐embedded (FFPE). To further investigate our hypothesis we also analyzed in our patient cohort the expression of the hepatocyte-specific miR-122. Results: We found no changes in miR-148a expression between primary and metastatic samples from 5 CRC patients with lung metastasis (p = 0.225). However, we observed that miR-148a was overexpressed in the metastatic tissues of those 12 CRC cases with liver metastasis (p = 0.019). Finally, MiR-122 was found markedly overexpressed in CRC liver metastases compared to the paired primary tumors (p < 0.001). Conclusions: Our results would suggest that restoration of miR-148a levels is a relevant molecular event that contributes to the establishment of the metastatic CRC cell in the liver. The short number of patients included is a limitation of this study. Thus, the potential role of miR-148a in CRC liver metastasis has to be further confirmed in forthcoming studies.