Background: Thymomas can benefit of cytoreductive surgery even if a complete resection is not feasible. The pleural cavity is the most common site of progression and the resection of pleural metastases can be performed in selected patients. We evaluated the results of stereotactic body radiation therapy for the treatment of pleural metastases in patients not eligible for surgery. Methods: We retrospectively selected 22 patients treated with stereotactic body radiation therapy for pleural metastases between 2013 and 2019. According to RECIST criteria 1.1 modified for thymic epithelial tumors, time to local failure and progression free survival were calculated using Kaplan-Meier method. Results: The median age was 40 years (range, 29-73 years). There were 1 A, 3 AB, 3 B1, 3 B2, 3 B2/B3 and 9 B3 thymomas. Pleural metastases and primary tumor were synchronous in 8 patients. Five patients had a single pleural metastatic site and 17 presented multiple localizations. Sixteen patients received stereotactic body radiation therapy on multiple sites of pleural metastases. The median dose of radiation was 30 Gy (range, 24-40 Gy). With a median follow-up of 33.2 months (95% CI: 13.1-53.3 months), ten patients experienced disease progression with a median progression free survival was 20.4 months (95% CI: 10.7-30.0 months). The disease control rate was 79% and 41% after 1 and 2 years, respectively. Local disease control rate was 92% and 78% after 1 and 2 years, respectively. There were not significant differences in progression free survival between patients diagnosed with synchronous and metachronous metastases (P=0.477), across those treated or not with chemotherapy (P=0.189) and between those who received or not a previous surgical resection of the pleural metastases (P=0.871). There were not grade 3-4 toxicities related to the treatment. Conclusions: Stereotactic body radiation therapy of pleural metastases is feasible and offers a promising local control of diseases. The impact of this treatment on patients' survival is hardly predictable because of the heterogeneous clinical behavior of thymomas.

Pembrolizumab has been approved as first-line treatment for advanced Non-small cell lung cancer (NSCLC) patients with tumors expressing PD-L1 and in the absence of other targetable alterations. However, not all patients that meet these criteria have a durable benefit. In this monocentric study, we aimed at refining the selection of patients based on the expression of immune genes. Forty-six consecutive advanced NSCLC patients treated with pembrolizumab in first-line setting were enrolled. The expression levels of 770 genes involved in the regulation of the immune system was analysed by the nanoString system. PD-L1 expression was evaluated by immunohistochemistry. Patients with durable clinical benefit had a greater infiltration of cytotoxic cells, exhausted CD8, B-cells, CD45, T-cells, CD8 T-cells and NK cells. Immune cell scores such as CD8 T-cell and NK cell were good predictors of durable response with an AUC of 0.82. Among the immune cell markers, XCL1/2 showed the better performance in predicting durable benefit to pembrolizumab, with an AUC of 0.85. Additionally, CD8A, CD8B and EOMES showed a high specificity (>0.86) in identifying patients with a good response to treatment. In the same series, PD-L1 expression levels had an AUC of 0.61. The characterization of tumor microenvironment, even with the use of single markers, can improve patients’ selection for pembrolizumab treatment.

BACKGROUND:HER2 overexpression has been investigated as a potential biomarker and therapeutic target in biliary tract cancer (BTC), but a prognostic role of such alteration has not been demonstrated yet.MATERIALS AND METHODS:We retrospectively evaluated HER2 protein expression by immunohistochemistry (IHC) in 100 patients with radically resected BTC. HER2 gene amplification was assessed by fluorescence in situ hybridization (FISH) in 2+ and 3+ cases at IHC. High HER2 protein expression was defined as either IHC 3+ or 2+ associated with FISH positivity. The primary objective of the study was to evaluate the prognostic role of HER2 overexpression in terms of disease-free survival (DFS) and overall survival (OS). Secondary endpoints were the prevalence of HER2 overexpression and the possible correlation with other clinicopathological features.RESULTS:HER2 overexpression was identified in 11 patients and was not related to other clinicopathological factors. DFS was significantly shorter in HER2-positive compared with HER2-negative patients (10.6 vs. 20.9 months, log-rank p = .017). HER2 confirmed its prognostic value for DFS at multivariate analysis (hazard ratio 2.512; 95% confidence interval, 1.232-5.125; p = .011) together with nodal stage (p < .001), resection margin (p = .027), and tumor site (p = .030). There was no difference in OS between HER2-positive and -negative patients (p = .068).CONCLUSION:HER2 overexpression represents an independent prognostic factor for disease recurrence in patients with BTC treated with potentially curative surgery.IMPLICATIONS FOR PRACTICE:HER2 overexpression may play an independent role in promoting an aggressive behavior in resectable biliary tract cancer. This evidence could be helpful in improving prognostic stratification after resection and, primarily, should endorse the rationale to investigate HER2 as a therapeutic target in biliary tract cancer.

Introduction Immune checkpoint inhibitors have provided substantial benefit in non-small cell lung cancer (NSCLC) with unprecedented results in terms of survival. However, the identification of reliable predictive biomarkers to these agents is lacking and multiple clinicopathological factors have been evaluated. The aim of this study was to analyze the potential role of neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and lactate dehydrogenase (LDH) levels in patients with pretreated NSCLC receiving nivolumab. Methods This was a retrospective multicenter study involving 14 Italian centers, evaluating the role of some laboratory results in patients with NSCLC treated with nivolumab in the second or later lines of therapy for at least four doses and with a disease re-staging. Results A total of 187 patients with available pretreatment laboratory results were included. NLR levels below 5 were associated with an improvement in terms of both progression-free survival (PFS) ( p = 0.028) and overall survival (OS) ( p = 0.001), but not in terms of overall response rate (ORR) or disease control rate (DCR). Moreover, PLR levels below 200 were associated with longer PFS ( p = 0.0267) and OS ( p = 0.05), as well as higher ORR ( p = 0.04) and DCR ( p = 0.001). In contrast, LDH levels above the upper normal limit (UNL) were not associated with significant impact on patient outcomes. Conclusions Patients with pretreated NSCLC and high pretreatment levels of NLR and PLR may experience inferior outcomes with nivolumab. Therefore, in this subgroup of patients with poor prognosis the use of alternative therapeutic strategies may be a valuable option, especially in programmed cell death ligand 1 (PD-L1)-negative patients and/or in the presence of other additional poor prognostic factors.

It is still unclear how to combine biomarkers to identify patients who will truly benefit from anti-PD-1 agents in NSCLC. This study investigates exosomal mRNA expression of PD-L1 and IFN-γ, PD-L1 polymorphisms, tumor mutational load (TML) in circulating cell-free DNA (cfDNA) and radiomic features as possible predictive markers of response to nivolumab and pembrolizumab in metastatic NSCLC patients. Patients were enrolled and blood (12 ml) was collected at baseline before receiving anti-PD-1 therapy. Exosome-derived mRNA and cfDNA were extracted to analyse PD-L1 and IFN-γ expression and tumor mutational load (TML) by digital droplet PCR (ddPCR) and next-generation sequencing (NGS), respectively. The PD-L1 single nucleotide polymorphisms (SNPs) c.-14-368 T > C and c.*395G > C, were analysed on genomic DNA by Real-Time PCR. A radiomic analysis was performed on the QUIBIM Precision® V3.0 platform. Thirty-eight patients were enrolled. High baseline IFN-γ was independently associated with shorter median PFS (5.6 months vs. not reached p = 0.0057), and levels of PD-L1 showed an increase at 3 months vs. baseline in patients who progressed (p = 0.01). PD-L1 baseline levels showed significant direct and inverse relationships with radiomic features. Radiomic features also inversely correlated with PD-L1 expression in tumor tissue. In subjects receiving nivolumab, median PFS was shorter in carriers of c.*395GG vs. c.*395GC/CC genotype (2.3 months vs. not reached, p = 0.041). Lastly, responders had higher non-synonymous mutations and more links between co-occurring genetic somatic mutations and ARID1A alterations as well. A combined multiparametric approach may provide a better understanding of the molecular determinants of response to immunotherapy.

Background: Immune-checkpoint inhibitors have radically changed the treatment landscape of Non-Small-Cell Lung Cancer (NSCLC). It is still unclear whether specific clinical characteristics might identify those patients benefiting from immunotherapy more than others. The aim of this study was to identify clinical characteristics associated with disease-specific survival (DSS), time-to-treatment failure (TTF), objective responses (OR) and progressive disease (PD) in NSCLC patients treated with Nivolumab.Methods: This was a multicenter retrospective study conducted on 294 patients treated with Nivolumab for advanced NSCLC.Results: Of the more than 50 variables analyzed, five showed a significant correlation with DSS: ECOG PS, size of the biggest brain metastasis, number of metastatic sites, toxicity, and malignant pleural effusion. Three variables significantly correlated with TTF: malignant pleural effusion, number of metastatic sites, number of liver metastases. Malignant pleural effusion was the only variable showing a significant correlation with OR, as well as the only one correlating with all the endpoints of the study.Conclusions: This study identified clinical characteristics associated with survival and response during treatment with Nivolumab in NSCLC patients. The unfavorable association between malignant pleural effusion and objective response is a novel finding with important translational implications.

In mesothelioma, chemotherapy with pemetrexed is effective but after progression the options of treatment have limited efficacy. Tumor associated macrophages are necessary for the growth of mesothelial tumors. Trabectedin is a tetrahydroisoquinoline alkaloid used for the treatment of sarcomas and ovarian cancer. Trabectedin interacts with the DNA double helix and interfere with the binding of transcription factors and polymerases, reprogramming gene expression in cancer and microenvironment cells. Therefore, we evaluated the effect of trabectedin in patients with mesothelioma after progression to standard treatments. We retrospectively identified 9 patients treated with trabectedin between 2017 and 2019. A continuous infusion of 1.5 mg/m2 of trabectedin was administrated in 24h every 21 days. According to RECIST criteria, overall survival (OS) and progression free survival (PFS) were calculated using Kaplan-Meier estimation. Seven of the 9 patients were male. The median age was 64 years (range 44-77). There were 6 epithelioid, 1 sarcomatoid and 2 biphasic mesotheliomas. The stage at diagnosis was III in 3 patients and IVB in 6 patients. Pleurectomy/decortication was performed in 5 patients, 4 patients received biopsy. The number of previous lines of chemotherapy was 1 in 4 patients, 2 in 2 subjects and 3 in 3 remaining. The median number of cycles was 3 (range 1-6). A grade 2 increase of transaminase was observed in 1 patient and a patient developed an atrial flutter with a heartrate of 180 during treatment. Two patients experienced G3 fatigue and fever. There were not G3-4 hematological toxicities but a G3 increase of creatine kinase was observed in 1 patient. Seven patients experienced a disease progression with a median PFS of 1.8 months (95%CI 1.55-2.05). The median OS was 5 months (95%CI 2.42-7.57). There were not significant differences in PFS and OS in relation to age, histology, sex, performance status, across patients treated with one or more lines of chemotherapy and between those who received pleurectomy Trabectedin in pre-treated mesothelioma patients is feasible with a moderate toxicity but there is no meaningful clinical activity for this agent according to the previous report of ATREUS trial.

Early tumor shrinkage (ETS) and depth of response (DoR) predict favorable outcomes in metastatic colorectal cancer. We aim to evaluate their prognostic role in metastatic pancreatic cancer (PC) patients treated with first-line modified-FOLFIRINOX (FOLFOXIRI) or Gemcitabine + Nab-paclitaxel (GemNab). Hence, 138 patients were tested for ETS, defined as a ≥20% reduction in the sum of target lesions' longest diameters (SLD) after 6-8 weeks from baseline, and DoR, i.e., the maximum percentage shrinkage in the SLD from baseline. Association of ETS and DoR with progression-free survival (PFS) and overall survival (OS) was assessed. ETS was reached in 49 patients (39.5% in the FOLFOXIRI, 29.8% in the GemNab group; p = 0.280). In the overall population, ETS was significantly associated with better PFS (8.0 vs. 4.8 months, p < 0.001) and OS (13.2 vs. 9.7 months, p = 0.001). Median DoR was -27.5% (-29.4% with FOLFOXIRI and -21.4% with GemNab, p = 0.016): DoR was significantly associated with better PFS (9.0 vs. 6.7 months, p < 0.001) and OS (14.3 vs. 11.1 months, p = 0.031). Multivariate analysis confirmed both ETS and DoR are independently associated with PFS and OS. In conclusion, our study added evidence on the role of ETS and DoR in the prediction of outcome of PC patients treated with first-line combination chemotherapy.

Pembrolizumab is the first-line standard of care for advanced Non-Small Cell Lung Cancer (NSCLC) that have a PD-L1 expression level greater than 50%. In this prospective monocentric study, we evaluated how the expression levels of PD-L1 above 50% impact on the objective response rate. Thirty-four advanced NSCLC patients with a PD-L1 expression level greater than 50% treated with Pembrolizumab in first-line setting between 2017 and 2019 were enrolled in this study. Patient and tumor characteristics were correlated with treatment outcomes. Patients clinical evaluation has been performed every 3 months from the beginning of treatment. Responses were defined according to the Response Evaluation Criteria in the Solid Tumors guidelines, version 1.1. Tumor assessments were performed locally. The mutational status of KRAS, BRAF, NRAS, PIK3CA, ALK, ERBB2, DDR2, MAP2K1, EGFR and RET was determined using a Mass Spectrometry assay. PD-L1 expression levels among the objective response groups were compared by Kruskal-Wallis test. A logistic regression model was used to evaluate the impact of PD-L1 expression levels above 50% on the objective response using mutational status, age, smoking habits, presence of toxicities, performance score and histology as confounders. Thirteen patients had partial response (PR), 12 stable disease (SD) and nine progression disease (PD). Nine out of 34 tumours harboured KRAS mutations; no alterations were found in the other tested genes. PD-L1 expression levels were different among the objective response groups (P=0.01) with the PR and PD groups having the highest (median 80%, IQ range 80-90%) and the lowest (median 60%, IQ range 60-70%) expression respectively (Figure 1). In the multivariate analysis, PD-L1 level was the only significant predictor of objective response (P=0.03) with an odds ratio of 0.91 (95%CI 0.81-0.98). In our series, PD-L1 expression above 50% confirmed to be an imperfect biomarker; however, the higher is the expression level the better is the objective response. For this reason, it could be relevant to provide clinicians with the exact PD-L1 percentage. Further investigations are warranted to define the best cut-off to select patients for monotherapy or combination with chemotherapy.

e14054 Background: Immunotherapy has revolutionized the treatment of NSCLC. However, response rate is variable, with a substantial failure rate. Thus, the identification of predictive biomarkers of response to immunotherapy is an area of great interest. Methods: Patients with locally advanced or metastatic NSCLC treated with nivolumab or pembrolizumab were enrolled. Disease response was defined following RECIST criteria (v. 1.1). Four ml of plasma were collected for the analysis of exosomal mRNA levels of PD-L1 (e-PD-L1) and IFN-γ (e-IFN-γ) at baseline and at the time of first radiological assessment. Exosome isolation and mRNA extraction was obtained by the exoRNeasy kit (Qiagen, Valencia, CA). e-PD-L1 and e-IFN-γ were evaluated by the QX100 ddPCR (Bio-Rad, Hercules, CA) and expressed as allele frequency (%). Chest computed tomography (CT) scan at baseline was used for the radiomic analysis. Tumor segmentation was performed on DICOM-formed images taken from the picture archiving, and the regions of interest were delineated manually and analyzed using the QUIBIM SL software. Survival was calculated stratifying patients based on e-PD-L1 and e-IFN-γ median values. Results: Nivolumab was given to 17 patients as 2nd line and to 8 subjects as further line of treatment, while 13 patients received 1st line pembrolizumab. Median PFS was 11 vs 16.2 months (mos) in patients with baseline e-PD-L1 of < 0.3% vs ≥0.3%, respectively (p = 0.16). e-PD-L1 significantly increased in disease progression (PD) vs partial response (PR) and disease stabilization (SD) (p = 0.01) after 2 mos of treatment. In patients with e-IFN-γ ≥4.1% vs < 4.1% at baseline, median PFS was 5.6 mos vs not reached, respectively (p = 0.003). The multiparametric radiomic analysis identified the Cluster Prominence Value (CPV, p = 0.012) and the Cluster Shade Value (CSV, p = 0.034) as significantly correlated with treatment outcome. Moreover, the D2d parameter and e-IFN-γ were inversely correlated (p < 0,0001). CPV and D2d reflect the intra-tumor architecture, including necrosis, cell proliferation, and angiogenesis. Conclusions: Liquid biopsy data correlate with radiomic parameters and predict response to immunotherapy.

8565 Background: Thymomas but not thymic carcinomas can benefit of cytoreductive surgery even if a complete resection is not achievable. Surgical resection of pleural metastases, the most common site of progression, can be performed in selected patients. We evaluated the outcome of stereotactic body radiation therapy (SBRT) for treatment of pleural metastases in patients’ not eligible for surgery. Methods: We retrospectively identified 22 patients treated with SBRT for pleural metastases between 2004 and 2019. According to RECIST criteria, time to local failure and progression free survival (PFS) were calculated using Kaplan-Meier estimation. Results: Twelve of the 22 patients were male. The median age was 40 years (range 29-73). There were 1 A, 3 AB, 3 B1, 3 B2, 3 B2/B3 and 9 B3 thymomas. The Masaoka stage at diagnosis was IIA in 2, IIB in 7, III in 5, IVA in 7 and IVB in 1 patient. Pleural metastases and primary tumor were synchronous in 8 patients. Thymectomy was performed in 21 patients. Seven patients received pre-operative chemotherapy and 12 post-operative radiotherapy. One patient received chemotherapy and radiotherapy after a macroscopically incomplete thymectomy. Five patients had a single pleural metastatic site and 17 presented multiple localizations. Sixteen patients received SBRT on multiple sites of pleural metastases. At the time of the analysis a patient received SBRT exclusively on one of 3 pleural metastases. The median dose of radiation was 30Gy (range 25-40) given in 3 fractions. Ten patients experienced a progression of treated lesions with a median time to local failure of 25.5 months (95%CI 20.9-30.1). The median PFS was 20.4 months (95%CI 10.7-30). There were not significant differences in PFS between patients diagnosed with synchronous and metachronous metastases (p=0.477), across those treated with chemotherapy or naive (p=0.189) and between those who received or not a previous surgical resection of the pleural metastases (p=0.871). Conclusions: SBRT of pleural metastases is feasible and offer an interesting local control of diseases. The impact of this treatment on patients’ survival is hardly predictable because of the heterogenous clinical behavior of thymomas.

Introduction: Biliary tract cancer (BTC) represents a rare and heterogenic tumour with aggressive behaviour. Mismatch repair deficiency (dMMR) seems to be associated with favourable prognostic characteristics in different gastrointestinal cancer types but its prevalence and correlation with clinical and pathological features in biliary tract cancer remain unclear. The aim of this study is to determine the incidence and characteristics of dMMR in a large multicentric cohort of cholangiocarcinoma and to explore its putative prognostic role both in resectable and in advanced settings. Methods: We retrospectively evaluated mismatch repair (MMR) status in a cohort of 149 patients with BTC including intrahepatic (iCCA), perihilar (pCCA), distal (dCCA) cholangiocarcinoma and gallbladder cancer (GBC). Tumour sections were assessed by immunohistochemistry (IHC) for MLH1, PMS2, MSH2, and MSH6. A dMMR tumour was defined by the loss of expression of any of the four MMR proteins. The primary objective of the study was to evaluate the incidence of dMMR. Correlation between the presence of dMMR and different clinicopathological characteristics was evaluated by the Mann-Whitney test and Chi-square test. Association with chemotherapy activity in advanced disease setting was assessed by Chi-square test whereas log-rank test was used for correlation between MMR status and disease-free survival (DFS), progression free survival (PFS) and overall survival (OS). Results: Out of 149 enrolled patients, 67 had iCCA, 36 dCCA, 20 pCCA and 26 GBC; stage was 1 in 32, 2 in 40, 3 in 23 and 4 in 53 patients. At diagnosis 110 patients had resectable disease and were submitted to surgery (R0 90%, R1 8%, R2 2%). Among the patients with initially metastatic or recurrent disease, 60% received gemcitabine + platinum. Nine patients (7 diagnosed with resectable and 2 with metastatic disease) presented dMMR tumour (1 with loss of MLH1, 5 with loss of MLH-1 and PMS-2, 2 with loss of MSH-6 and 1 with loss of MLH-1, PMS-2 and MSH-6). Among the investigated characteristics, dMMR status was significantly correlated with tumour site (iCCA 11% vs others 2.4 %, p = 0.041) and mucinous histology (yes 50% vs no 4%, p0.005). Conclusion: A not negligible percentage of patients with BTC shows dMMR status. This seems to be more prevalent among patients with iCCA and tumours with mucinous histology. Putative poor prognostic role after potentially curative resection needs to be confirmed at longer follow up and in independent larger cohorts.

FOLFIRINOX (leucovorin, 5-fluorouracil, irinotecan, and oxaliplatin) is an accepted standard in metastatic and locally advanced pancreatic cancer (PC), but long-term prognosis is still poor. Indeed, no criteria reliably identify patients with limited, if any, chances of long-term benefit. We therefore developed and externally validated a prognostic nomogram predicting the risk of early death in PC patients treated with first-line triplet chemotherapy. Background: FOLFIRINOX (leucovorin, 5-fluorouracil, irinotecan, and oxaliplatin) is an option for fit patients with metastatic (MPC) and locally advanced unresectable (LAPC) pancreatic cancer. However, no criteria reliably identify patients with better outcomes. Patients and Methods: We investigated putative prognostic factors among 137 MPC/ LAPC patients treated with triplet chemotherapy. Association with 6-month survival status (primary endpoint) was assessed by multivariate logistic regression models. A nomogram predicting the risk of death at 6 months was built by assigning a numeric score to each identified variable, weighted on its level of association with survival. External validation was performed in an independent data set of 206 patients. The study was registered at ClinicalTrials.gov (NCT03590275). Results: Four variables (performance status, liver metastases, baseline carbohydrate antigen 19-9 level, and neutrophil-to-lymphocyte ratio) were found to be associated with 6-month survival by multivariate analysis or had sufficient clinical plausibility to be included in the nomogram. Accuracy was confirmed in the validation cohort C index = 0.762; 95% confidence interval, 0.713-0.825). After grouping all cases, 4 subsets with different outcomes were identified by 0, 1, 2, or > 2 poor prognostic features (P <.0001). Conclusion: The nomogram we constructed accurately predicts the risk of death in the first 6 months after initiation of FOLFIRINOX in MPC/LAPC patients. This tool could be useful to guide communication about prognosis, and to inform the design and interpretation of clinical trials. (C) 2019 Elsevier Inc. All rights reserved.

Introduction: The impact of sarcopenia as a predictor of poor prognosis and its association with chemotherapy toxicity have been explored in different cancer types but remain controversial in mGC. Our aim was to explore the correlation between sarcopenia, evaluated at baseline CT scan, and toxicity and efficacy of first-line therapy. Methods: We retrospectively analyzed pre-treatment CT scans from 78 mGC patients treated with first-line doublet chemotherapy comprising oxaliplatin and 5-fluorouracil/leucovorin or capecitabine (trastuzumab was administered in case of HER2-positive disease). Sarcopenia was defined according to previously published criteria (Martin L et al. J Clin Oncol 2013) by the use of the skeletal muscle index (SMI) and body mass index (BMI), according to gender-specific cut-off values. SMI was calculated as follows: cross-sectional skeletal muscle area (SMA) measured at the level of the third lumbar vertebra / (height)2 (m2). Toxicities were graded according to NCI CTCAE v.4.0. Association between the presence of sarcopenia and different adverse events was evaluated by Chi-square test. Correlation with response rate (RR, evaluated according to RECIST criteria 1.1), progression-free survival (PFS) and overall survival (OS) was assessed by the use of the log-rank test. Results: Sarcopenia was evident in 34 (44%) patients. We observed a significant association between the presence of sarcopenia at baseline assessment and a higher risk of severe (i.e. grade 3-4) neutropenia (38% versus 18%; p = 0.048) and a higher risk of any grade mucosal toxicities (56% versus 34%; p = 0.045). None of the other investigated clinical factors (comprising age, gender, performance status, sites of metastases and previous surgery on primary tumor) was associated with the risk of toxicity. Neither sarcopenia nor the other evaluated clinical parameters were associated with outcome as measured by RR, PFS, and OS: the only exception was performance status, which was confirmed a major prognostic determinant in terms of PFS and OS. Conclusion: Our experience identified sarcopenia as a potential determinant of the risk of hematologic and mucosal toxicities from first-line platinum plus fluoropyrimidine chemotherapy in mGC patients. Sarcopenia was apparently not associated with benefit from treatment and survival, but larger studies are needed to address this issue. Strategies aiming at improving the nutritional status of mGC patients are warranted to optimize the risk-to-benefit ratio of available treatments.

Introduction: The combination of paclitaxel and ramucirumab represents the standard second-line treatment for advanced gastroesophageal cancer. To date, no prognostic or predictive biomarkers have been identified in this setting. The aim of this study was to explore the association of the baseline levels of circulating angiogenesis-related factors and their modifications during treatment with the benefit of second-line paclitaxel plus ramucirumab. Methods: Patients with advanced gastric or gastro-esophageal junction carcinoma undergoing second-line treatment with paclitaxel and ramucirumab at our centre were prospectively enrolled. Four ml of plasma were obtained at day 1 and 15 of the first 3 cycles (before treatment administration), at the time of best radiologic response (according to RECIST 1.1 criteria) and at disease progression. Evaluation of vascular endothelial growth factor (VEGF) -A (VEGF-A) and -D (VEGF-D) and soluble vascular endothelial growth factor receptor-2 (sVEGFR2) was performed using ELISA kits. Correlation of biologic data and additional clinical or pathologic features with response rate (RR), progression-free survival (PFS) and overall survival (OS) was explored by the use of chi-square test and log-rank test, as appropriate. Results: A total of 41 patients were enrolled in the study. At a median follow up of 16.1 months, median PFS and OS were 5.6 and 15.1 months, respectively. RR was 26.8% and DCR was 63.4%. Levels of VEGF-A and VEGF-D significantly increased during treatment compared to baseline (p < 0.001), while sVEGFR-2 values did not significantly change at any time point. A positive correlation between VEGF-A and sVEGFR2 at day 1 of cycle 2 was found (Pearson's r = 0.3465, p = 0.045). At univariate analysis, none of the collected clinicopathologic features was associated with outcome. Among the investigated circulating biomarkers, higher baseline levels of VEGF-A (≥ the median value of 26.90 pg/ml) were associated with worse OS (median: 6 versus 19.5 months, p = 0.015). Moreover, the increase of sVEGFR2 from baseline to cycle 2-day 1 was associated with longer PFS (median: 6.6 versus 3.6 months, p = 0.049) and OS (median: 18.6 versus 5.2 months, p = 0.008). No significant correlations were found for VEFG-D. The significant impact of sVEGFR2 increase on OS was retained at multivariate analysis comprising also baseline VEGF-A levels (p = 0.032; HR = 0.32, 95%CI 0.11-0.91). Conclusion: In metastatic gastroesophageal cancer patients receiving second-line paclitaxel plus ramucirumab, baseline VEGF-A level was confirmed as a poor prognostic marker. Notably, sVEGFR2 dynamics after 1 cycle could represent a potential predictive factor for the identification of patients with higher chances of benefit from treatment: further validation in a larger cohort is needed.

210 Background: The anti-PD-1 monoclonal antibodies (moAb) nivolumab and pembrolizumab have improved the survival of melanoma and non-small cell lung cancer (NSCLC) patients. However, treatment selection is based on tumor PD-L1 expression by immuno-histochemistry and no specific approaches are available to monitor treatment response. The aim of this study was to investigate the association between PD-L1 mRNA levels in plasma-derived exosomes and response to nivolumab and pembrolizumab in patients affected by melanoma (n = 18) and NSCLC (n = 8). Methods: Blood (6 ml) was obtained at 1) baseline (before initiation of anti-PD1 moAb or at the time of last available radiological evaluation of disease response) and 2) after two months of treatment (at the time of first response evaluation or disease re-assessment). Exosomes were extracted from plasma and PD-L1 mRNA expression was measured by digital PCR and expressed as copies/ml. Results: Overall, the number of copies of mRNA PD-L1/ml plasma varied according to tumor response; in particular, an increase was found in patients with PD and a decrease was observed in patients who achieved a CR/PR. The mean±SEM values of PD-L1 in patients responding to treatment (CR+PR) were 830.4±231.3 and 242.5±82.5 copies/ml (baseline vs. 2 months, p = 0.016), respectively. In patients with stable disease the mean±SEM values were as expected 298.8±97.2 vs. 247.5±29.8 copies/ml (p = 0.586), while in progressive disease PD-L1 expression levels were 204.0±68.8 vs. 416.0±87.8 copies/ml (p = 0.001), respectively. Conclusions: In the present study, we demonstrate for the first time that changes in exosomal PD-L1 expression occur in melanoma and NSCLC patients treated with nivolumab or pembrolizumab and may correlate with the radiological tumor response. This proof-of-concept study demonstrates the feasibility of detecting PD-L1 in plasma and its relationship with response to treatment.

Background: In lung adenocarcinoma, activating mutation of EGFR (aEGFR) and EGFR-T790M can coexist. T790M confers resistance to 1st and 2nd generation TKIs, the standard 1st line treatment. T790M may also be observed at diagnosis (preT790M+) in 0,5-3% cases using standard techniques and up to 30% with highly sensitive ones. FDA and EMA approved osimertinib, a 3rd generation TKI overcoming T790M resistance, for 2nd-line in patients T790M+. Recently FDA approved it for 1st-line of aEGFR+ metastatic disease. Current guidelines make no distinction in aEGFR patients with or without preT790M+. In the osimertinib era it becomes important to detect properly T790M at diagnosis and to define the best strategy for preT790M+. The aim of this study was to find differences in terms of survival and response rate between preT790M+ and wild-type for T790M (WT), detecting T790M with a highly sensitive technique. Methods: We selected aEGFR+ lung adenocarcinoma who received 1st or 2nd generation TKI in 1st line treatment in our Institution. We reanalyzed the tumor samples of the diagnosis with RainDrop Digital PCR. For statistical analysis we used Kaplan-Meyer method and log-rank test. Results: We analyzed tumor samples of 28 subjects. At diagnosis, all were wild-type for T790M with standard techniques. With RainDrop Digital PCR, preT790M+ were 28,6% (n = 8). In ≥ 2nd lines 50% of preT790M+ and 30% of WT received osimertinib, according to T790M detection after progression. 1-yr and 2-yr survival were, respectively, 100% and 89% for preT790M+; 68% and 60% for WT. Median OS (mOS) of preT790M+ was not reached at the end of followup and 32.7 months for WT (p = 0.098). There were no differences in mOS stratifying by osimertinib use the study population (p = 0.792) and preT790M+ subgroup (p = 1.000). RR was 87,5% for preT790M+, 60% for WT (p = 0.241). Median PFS was 10,4 months for preT790M+, 13.3 months for WT (p = 0.721). Conclusions: Our data, with the limits of the small sample size, show that the coexistence at diagnosis of aEGFR and T790M is not negligible. PreT790M+ tumors could represent a more indolent disease. Further studies are needed to define the optimal timing for osimertinib in these patients. Legal entity responsible for the study: University of Pisa, Italy. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.

Introduction: HER2 currently represents the only available predictive biomarker in advanced esophagogastric cancer. Trastuzumab plus chemotherapy is the standard of care in tumors carrying HER2 protein overexpression by immunohistochemistry (IHC) or gene amplification by in situ hybridization (ISH). However, heterogeneity in protein expression, lack of adequate tumor samples for analyses and the need for rapid target assessment for patient management underline the need for a pre-test screening tool in order to anticipate the probability of carrying a HER2-positive disease. Methods: The clinical and pathological data from 695 consecutive esophagogastric carcinomas analyzed at three different Institutions were collected. HER2 positivity was defined as IHC score of 3+ or 2+ with a positive ISH. 411 cases from one Institution were used to build a multivariate logistic regression model able to predict HER2 positivity. Both backwards and forward method were used to build multiple models. Collinearity was evaluated with Fisher’s test, t-test and ANOVA, depending on the nature of the covariates, and Variance Inflation Factor (VIF). Final model was selected considering statistical significance of the covariates, clinical plausibility and global fit and it was used to develop a nomogram. Validation and calibration were performed on an external series of 284 patients treated at other two Institutions. C-index, visual inspection of the calibration plot, Brier score and Spiegelhalter z-test were used to assess the performance of the nomogram. 95% confidence intervals (CIs) of C-index were calculated with bootstrap method. Results: 119 cases (17%) showed HER2 positivity in the development cohort. After univariate analyses and adjustment of collinearity, four variables were introduced in the final model: tumor grading (G1 vs. G2 vs. G3) (p = 0.0018), Lauren’s histotype (intestinal vs. diffuse) (p = 0.044), type and adequacy of pathological material (surgical specimen vs. ≥5 biopsy samples vs. <5 biopsy samples) (p = 0.19) and site of sampling (primary cancer vs. metastasis) (p = 0.034). Tumor grading was associated to the greatest number of points, followed by site of sampling, Lauren's histotype and type of pathologic material. Visual inspection of the calibration plot revealed a very good overlap between predicted and observed probabilities, with a Brier score of 0.048 and a statistically significant Spiegelhalter z-test (p < 0.0001). C-index resulted in 0.84 (95%CI 0.75-0.93). Conclusion: We developed a simple nomogram based on four immediately and always available pathological characteristics able to accurately predict the probability of HER2 positivity in esophagogastric cancer. This could be useful to minimize HER2 test heterogeneity and prompts re-biopsy in those cases of inadequate material but an anticipated high probability of HER2 positive status. A visual format of the nomogram will be presented.

PURPOSE: The evaluation of molecular targets in gastric cancer has demonstrated the predictive role of HER2 amplification for trastuzumab treatment in metastatic gastric cancer. Besides HER2, other molecular targets are under evaluation in metastatic gastric tumors. However, very little is known about their role in resected tumors. We evaluated the expression of HER2, EGFR, MET, AKT1 and phospho-mTOR in resected stage II-III adenocarcinomas. METHODS: Ninety-two patients with resected stomach (63%) or gastro-esophageal adenocarcinomas (27%) were evaluated. Antibodies anti-HER2, EGFR, MET, AKT1 and phospho-mTOR were used for immunostaining of formalin-fixed paraffin-embedded slides. Using FISH, HER2 amplification was evaluated in cases with an intermediate (+2) staining. RESULTS: EGFR overexpression (11%) was a poor prognostic factor for overall survival (3-year OS: 47% vs 77%; Log-Rank p = 0.033). MET overexpression (36%) was associated with a trend for a worse survival (3-year OS: 65% vs 77%; Log-Rank p = 0.084). HER2 amplification/overexpression and mTOR hyper-phosphorylation were observed in 13% and 48% of tumors, respectively. AKT1 overexpression (8%) was not a prognostic factor by itself (p = 0.234). AKT1 and EGFR overexpression was mutually exclusive and patients with EGFR or AKT1 overexpression experienced a poor prognosis (3-year OS: 52% vs. 79%, Log-Rank p = 0.005). CONCLUSIONS: EGFR is confirmed a poor prognostic factor in resected gastric cancers. We firstly describe a mutually exclusive overexpression of EGFR and AKT1 with potential prognostic implications, suggesting the relevance of this pathway for the growth of gastric cancers.

e24128 Background: Pancreatic ductal adenocarcinoma (PDAC) is considered a poorly immunogenic tumor and treatment with immune checkpoint inhibitors lacks efficacy in this disease. Recently, the use of immune checkpoint inhibitors with radiation therapy in PDAC has demonstrated synergistic activity (1). The aim of this study was to evaluate the effect of FOLFIRINOX and GEMnPAC on PD-L1 expression in plasma-derived exosomes of PDAC patients. Methods: Four ml of plasma were obtained at baseline (before initiation of chemotherapy) and at the time of first radiological evaluation (3 months) from patients undergoing first-line FOLFIRINOX or GEMnPAC chemotherapy. Exosomes and RNA extraction from plasma were performed using the exoRNeasy kit (Qiagen, Valencia, CA, USA); PD-L1 expression was evaluated by digital droplet PCR (Bio-Rad, Hercules, CA, USA). Results: A total of 22 pancreatic cancer patients were enrolled in this study; 15 (68.2%) were treated with GEMnPAC and 7 (31.9%) with FOLFIRINOX. In the GEMnPAC group one patient had a partial response (RP), 11 patients had stabilization of disease (SD) and 3 progressed (PD). In the FOLFIRINOX group there were 1 RP, 5 SD and 1 PD. Eleven patients treated with GEMnPAC had a significant increase of PD-L1 expression at 3 months vs. baseline. Indeed, the mean PD-L1 copies/ml was 90 at baseline and 170 at 3 months (p = 0.02). On the contrary, in the FOLFIRINOX group, PD-L1 levels were increased in 3 patients and remained stable/decreased in 4 subjects; the mean baseline copies/ml were 70 vs. 80 at 3 months (p = 0.4). The selective induction of PD-L1 expression was independent from tumor response. Conclusions: These pilot data suggest that, due to its ability to increase PD-L1 expression, GEMnPAC regimen may be used as induction-treatment for immunotherapy in pancreatic cancer, either sequentially or concomitantly. References 1. Azad A, Yin Lim S, D'Costa Z, Jones K, Diana A, Sansom OJ, Kruger P, Liu S, McKenna WG, Dushek O, Muschel RJ, Fokas E. PD-L1 blockade enhances response of pancreatic ductal adenocarcinoma to radiotherapy. EMBO Mol Med 2017;9(2):167-180