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e21144 Background: Immune-checkpoint inhibitors (ICIs) have revolutionized the therapeutic landscape of lung cancer patients. However, its low treatment efficacy is still an issue and the current standard of care tissue PD-L1 presents high variability. Liquid biopsy is a promising tool in the discovery of biomarkers in body fluids. In particular, extracellular vesicles (EVs) can present PD-L1 in their membranes, playing a role in the inhibition of the anti-tumor immune response. Likewise, TGF-β is crucial in the immune response found in the circulation and into EVs. On the other hand, radiomics analysis of conventional imaging provides information about tumor heterogeneity and immune response. Hence, we aimed to evaluate the predictive role of circulating biomarkers in lung cancer patients undergoing ICIs and the additional value of radiomics data. Methods: This is a retrospective analysis of 30 advanced/metastatic non-small lung cancer patients treated with ICIs. Plasma samples were collected at baseline and at 8 weeks during treatment, matching the first response evaluation. Patients with complete, partial response, or stable disease were classified as responders and those with progressive disease as non-responders following RECIST v1.1. EVs were isolated from plasma by ultracentrifugation and PD-L1 expression was revealed by immunoblot. Circulating and EV levels of TGF-β were analyzed by ELISA. Additionally, 400 radiomics features from target and non-target lesions were analyzed to evaluate response in 24 patients according to RECIST v1.1 and irRECIST. Robustness of predictive models was validated by ridge penalty and leave-one-out cross-validation. Results: The analysis of the dynamics of EV PD-L1 during treatment identified increased levels in non-responders in comparison to responders ( p= 0.012), while tissue PD-L1 levels were not associated to the response ( p= 0.585). The predictive model for EV PD-L1 reported a high accuracy with an area under the curve (AUC) = 77%, 91.7% sensitivity, and 61.1% specificity. The combination with radiomics, improved the accuracy and reported an AUC = 83%, 82% sensitivity, and 77% specificity. Additionally, the analysis of the association of the circulating biomarkers with the outcome revealed that increasing dynamics of EV PD-L1 and high baseline EV TGF-β were associated with shorter progression-free survival and overall survival, outperforming the circulating levels of TGF-β. Conclusions: This pilot study demonstrated that EV PD-L1 could serve as better predictive factor than tissue PD-L1 for the stratification of lung cancer patients undergoing ICIs and that it could be complemented with radiomics. Moreover, EV levels of PD-L1 and TGF-β have potential for the stratification and prognosis of patients treated with ICIs and their novel combinations with TGF-β blockade.

PURPOSE To determine whether bone scan, magnetic resonance imaging (MRI), or somatostatin receptor scintigraphy (SRS) is best for identifying bone metastases in patients with gastrinomas, as well as their frequency and location, whether their detection affects management, and what patient subgroups should be examined. MATERIALS AND METHODS One hundred fifteen patients with gastrinoma were prospectively studied. Patients were examined yearly and those with liver metastases were reexamined every 3 months. Based on clinical history, histology, growth pattern, and development of new bone lesions, possible bone metastases were classified as to whether they were or were not bone metastases. Imaging results were correlated at different times in the disease course and with disease extent. RESULTS Bone scan was positive in 52 patients, MRI in seven, and SRS in six. Eight patients (7%) were determined to have bone metastases and MRI was correctly positive in seven, SRS in six, and bone scan in five. SRS or MRI was positive in all patients with bone metastases. Bone scan had significantly lower specificity and sensitivity, and a higher rate (P < .02) of false-negative results than MRI or SRS. Bone metastases occurred in 31% of patients with liver metastases and 0% with only lymph node metastases. The initial bone metastases were in the spine or sacrum (75%) followed in descending order by the pelvis or sacroiliac joints (38%), scapula or shoulder, and ribs. In all cases, detection of bone metastases changed the management. CONCLUSION SRS and MRI, because of high sensitivity and specificity, are recommended over bone scanning to screen for bone metastases in patients with gastrinomas. However, because bone metastases can occur initially outside the axial skeleton, SRS is the recommended initial localization method of choice. Bone metastases occur in 7% of all patients and 31% of patients with liver metastases, only occur in patients with liver metastases, are usually in the axial skeleton initially, and their detection changes management in all cases. Patients with pancreatic endocrine tumors with liver metastases should undergo SRS every 6 months to 1 year to detect bone metastases.

PURPOSE The growth pattern of untreated metastatic neuroendocrine tumors is unknown. This uncertainty contributes to the disagreement regarding timing and could effect evaluation of the efficacy of antitumor treatment. The purpose of this study was to determine the growth rate of untreated hepatic metastatic gastrinoma and to identify its predictors. PATIENTS AND METHODS Nineteen patients with histologically proven metastatic gastrinoma in the liver with Zollinger-Ellison syndrome were studied. Conventional imaging studies were performed initially and at 4- to 6-month intervals before any treatment. Metastases growth rates were calculated and correlated with laboratory and clinical parameters, as well as tumor extent on initial tumor assessment. RESULTS Twenty-six percent of patients (five of 19) demonstrated no growth over a mean follow-up time of 29 months, 32% (six of 19) had slow growth (1% to 50% increase in volume per month) over a 19-month period, and 42% (eight of 19) had rapid growth (> 50% volume increase per month) over an 11-month period. In patients with rapid growth, 62% died; 0% of the no-growth or slow-growth group died. No clinical or laboratory parameter correlated with growth rate, except the rate increase in fasting serum gastrin and the presence of bilobar liver or bone metastases. The growth rate was highly predictive of death from tumor. CONCLUSION The growth rate of metastatic gastrinoma varies markedly in different patients and 26% demonstrate no growth. The growth rate needs to considered in the determination of when and in whom antitumor therapy is initiated, as well as in the assessment of response to tumoricidal therapies.

e22025 Background: To develop clinical applications of Circulating Tumor Cells (CTC), their phenotypic and genetic characterization is required. Here, we present the first protocol to detect miRNAs...

e22026 Background: The Metastasis process is associated with the presence of Circulating Tumor cells (CTCs) in peripheral blood of colon cancer patients. However, biologic characteristics of CTC an...

10608 Background: Angiotensin type 1 receptor (AGTR1) is a membrane receptor implicated in the regulation of arterial pressure. It has also been related to carcinogenesis and tumor spread, and participates in neoangiogenesis. AGTR1 is expressed in a number of neoplasms as BC. In a previous neoadjuvant study, a significant relationship was observed between AGTR1 expression and CR to a regimen of chemo and bevacizumab (B). To study and confirm the relationship between tumor expression of AGTR1 and response to a regimen of chemo and B in pts with mBC. Methods: AGTR1 expression was subjected to immunofluorescence (monoclonal AGTR1 sc1173 antibody, Santa Cruz Biotechnology, CA, USA Dilution 1:50) in 50 samples of mBC pts from the AVALUZ study treated with first line bevacizumab 10 mg/kg, paclitaxel 150 mg/m2 and gemcitabine 2000 mg/m2 d 1 and 15 c/28 d until PD, unacceptable toxicity or medical decision. Immunoreactivity was reported as negative (0), low positive (1+) and high positive (2+). RNA was extracted from paraffin blocks, using the QIAamp DNA FFPE Tissue Kit and Deparaffinization Solution (QIAGEN) and expression of AGTR1 candidate gene was quantified using reverse transcription-PCR (RT-PCR). Results: 60% of the samples expressed AGTR1 (26% weak and 34% intense) – expression being more frequent in HR + tumors (65% vs 45%). Among the 50 samples analyzed, measurable disease was present in 39 pts. Treatment activity was significantly greater in the tumors AGTR1 expression 2+ (p=0.009) (Table). With a median follow-up of 19.30 months, the progression-free interval was longer in the tumors with intense AGTR1 expression (17.7 vs 10.8 months, p=0.132). More consolidated PFS and OS will be presented. Conclusions: AGTR1 expression may be useful as a predictor of response to chemo and bevacizumab. Prospective studies are needed to confirm these findings. [Table: see text]