ObjectivesTo describe our experience with non‐invasive prenatal testing (NIPT) in twin pregnancy.MethodsTwo sets of maternal blood samples from twin pregnancies were analyzed at our laboratory using NIPT: 115 stored samples from pregnancies with known outcome (Clinical Study A) and 487 prospectively collected samples for which outcomes were requested from providers (Clinical Study B). NIPT was used to screen for the presence of fetal aneuploidy on chromosomes 13, 18, 21, X and Y in all cases, and results were compared with outcomes when known.ResultsIn Clinical Study A, all 115 samples were classified correctly by NIPT: three cases of trisomy 21 (one fetus affected), one of monochorionic trisomy 18 (both fetuses affected) and 111 euploid. In Clinical Study B, a NIPT result was reported for 479 (98.4%) of the 487 samples. Aneuploidy was detected or suspected in nine (1.9%) cases: seven cases of trisomy 21 detected, one case of trisomy 21 suspected and one case with trisomy 21 detected and trisomy 18 suspected. Information on aneuploidy outcome was available for 171 (35.7%) cases in Clinical Study B. Of the nine cases with aneuploidy detected or suspected, six were confirmed to be a true positive in at least one twin based on karyotype or birth outcome and two were suspected to be concordant based on ultrasound findings; the one known discordant result was for the aneuploidy suspected case. No false negatives were reported.Conclusion NIPT performed well in the detection of trisomy 21 in twin pregnancy, with a combined false‐positive frequency for trisomies 13, 18 and 21 of 0% for Clinical Study A and 0.2% for Clinical Study B. © 2016 Illumina. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

9510 Background: Sym015, a mixture of 2 humanized antibodies, triggers MET degradation by a unique mechanism with superior specificity compared to tyrosine kinase inhibitors (TKIs). The Sym015-01 phase (P)1a trial met, the primary objective of identifying the recommended P2 dose (RP2D) as 18 mg/kg on cycle 1 day 1 followed by 12 mg/kg Q2W. The P2a was expanded to enroll METAmp/Ex14∆ NSCLC patients (pts) based on preliminary efficacy findings. Here we present interim safety (n = 45) and efficacy (NSCLC cohort, n = 20) results from P2a. Methods: The expansion NSCLC Cohort enrolled pts with METEx14Δ (n = 12) or METAmp (n = 8 defined as > 5 MET copies by NGS or MET/CEP7 ratio > 2.2 updated to ≥3.0 by in situ hybridization; including 1 with METAmp+Ex14Δ). Tumor MET status was confirmed centrally and longitudinal ctDNA was analyzed by Guardant360. Results: By January 2020, 45 pts (median age 61.7 years) have been treated in P2a. Median duration of exposure (DoE) was 3.8 months (m) (n = 45; range 0.4+ to 22 m). Treatment emergent adverse events occurred in 93%, treatment related AEs (TRAE) in 42.2% and TRAE ≥G3 in 13.3% pts. No pts discontinued or died due to TRAE. The most common TRAE in ≥10% pts were fatigue (13.3%) and peripheral edema (11.1%). Of 20 NSCLC pts, 5 had confirmed PR (ORR 25%; 2/8 METAmp and 3/12 METEx14Δ); 11 had SD (DCR 80%; 6/8 METAmp and 5/12 METEx14Δ); 2 had PD (2/12 METEx14Δ); and 2 were not evaluable. 10 NSCLC pts were MET TKI naive (7 METAmp and 3 METEx14Δ) and had 50% ORR and 100% DCR (5 PR and 5 SD; DoR range 1 to 18.3 m; DoE 1.5 to 22 m); 10 NSCLC pts were prior MET TKI treated (9 METEx14Δ and 1 METAmp+Ex14Δ) with DCR 60%, (6 SD; DoE 0.4-9.6 m). Median PFS was 5.5 m overall (95% CI 3.5-9.7 m). Median PFS for MET TKI naive and MET TKI pre-treated NSCLC pts was 6.5 m (95% CI 3.4-21.9 m) and 5.4 m (95% CI 1.2-9.7 m) respectively. Median OS was not reached for overall or for prior MET TKI subgroups. 89% METEx14∆ tumor tissue to blood concordance (8/9 NSCLC pts) was observed. Conclusions: Sym015 was well-tolerated at the RP2D with a response rate similar to MET TKI in MET-treatment naïve METAmp/Ex14Δ NSCLC and seems to delay disease progression in MET TKI pretreated NSCLC pts. Combination with MET TKI to delay or prevent resistance should be further explored. Clinical trial information: NCT02648724 .

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Electronic poster abstracts than 95th percentile (OR 13.593, p = 0.001) are independently correlated with miscarriage. Conclusions: This study has newly presented that a small 3D GS volume for gestational age is a significant ultrasonographic predictor for subsequent miscarriage as well as fetal bradycardia, a small GS diameter, and a small YS diameter. P01.16Non-invasive prenatal testing experience in a clinical laboratory: rate of aneuploidy in fetuses with an increased nuchal translucency of ≥3.5mm L. Fosler, A. SwansonIllumina, Inc., Redwaood City, CA, USA Objectives: The association between increased fetal nuchal translucency (NT) thickness and fetal aneuploidy is well known. Noninvasive prenatal testing (NIPT) by maternal blood DNA sequencing is highly sensitive and specific for detecting Trisomies 21, 18, 13 and monosomy X (MX). While it has been suggested by Bianchi et al. 2013 that NIPT provides an accurate way of detecting common aneuploidies associated with cystic hygroma (CH), results from a clinical laboratory setting for indications of increased NT or CH have not been reported. Methods: A query of our clinical laboratory database was performed to identify samples with an indication of increased NT (≥3.5mm) or CH. Results were reviewed and aneuploidy rates were compared to those determined by Kagan et al. 2006, who also assessed aneuploidy incidence in fetuses with increased NT, regardless of CH status. Results: During the study period, 99 samples had an indication of increased NT (n=45) or CH (n=54). Aneuploidy was detected or suspected in 38 cases (38.3%) (table 1). Of note, 9 of 10 samples with MX detected were documented as having CH, and one sample with MX also had aneuploidy suspected for Trisomy 13. The aneuploidy rate in the CH cohort alone was 51.9%. Conclusions: Clinical laboratory experience with NIPT for fetuses with increased NT or CH shows aneuploidy rates consistent with published findings from invasive testing. The observed rate of aneuploidy detection in the CH cohort is higher than that in increased NT alone and comparable to our previously published data. These observations support the conclusion that results from clinical laboratory NIPT are within expectations for an indication of increased NT. P01 P01.17Role of laboratory markers and ultrasound parameters in prediction of preterm delivery Department of Obstetrics and Gynecology, Clinical Centre of Vojvodina, Novi Sad, SerbiaObjectives: Aim of study: was to determine if values of laboratory markers of chromosomal abnormalities as well as ultrasound parameters in early pregnancy can be helpful in detection of pregnant women at risk of preterm delivery. Methods:The study included the total of 229 pregnant women divided in two groups; the study group (n = 73) and the control group (n = 156). The study group consisted of pregnant women who delivered before week of gestation (WG) 37, (36 + 6WG), while the control group consisted of pregnant women who delivered after GW37. (37 + 1WG). All pregnant women were monitored from the fir...