BackgroundProgrammed death-ligand 1 (PD-L1) monoclonal antibody therapy has recently gained approval for treating metastatic triple-negative breast cancer (TNBC) -, in particular in the PD-L1+ patient subgroup of the recent IMpassion130 trial. The SP142 PD-L1 antibody clone was used as a predictive assay in this trial, but this clone was found to be an outlier in previous harmonisation studies in lung cancer.AimsTo address the comparability of PD-L1 clones in TNBC, we evaluated the concordance between conventional immunohistochemistry (IHC) and multiplex immunohistochemistry/immunofluorescence (mIHC/IF) that allowed simultaneous quantification of three different PD-L1 antibodies (22C3, SP142 and SP263).MethodsOur cohort comprised 25 TNBC cases, 12 non-small-cell lung carcinomas and 8 other cancers. EpCAM labelling was used to distinguish tumour cells from immune cells.ResultsModerate-to-strong correlations in PD-L1 positivity were found between results obtained through mIHC/IF and IHC. Individual concordance rates in the study ranged from 67% to 100%, with Spearman’s rank correlation coefficient values up to 0.88.ConclusionsmIHC/IF represents a promising tool in the era of cancer immunotherapy, as it can simultaneously detect and quantify PD-L1 labelling with multiple antibody clones, and allow accurate evaluation of tumour and immune cells. Clinicians and pathologists require this information to predict patient response to anti-PD-1/PD-L1 therapy. The adoption of this assay may represent a significant advance in the management of therapeutically challenging cancers. Further analysis and assay harmonisation are essential for translation to a routine diagnostic setting.

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730 Background: Tumoral KRAS mutations (KRAS mt) are detected in ~80% of APC and associated with a negative prognosis. Digital droplet PCR (ddPCR) has high sensitivity for circulating KRASmtbut narrower gene coverage. NGS using hybrid-capture methods has reported ctDNA KRASmtin ~30% of patients (pt). We previously presented clinical results of the Phase I trial of OXIRI (GI ASCO 18 #411). We now present the first prospective evaluation of ctDNA in APC by an amplicon-based NGS approach in this Phase I trial. Methods: Paired ctDNA and CA19-9 samples were taken at baseline, C2D1, C3D1 and end of trial. A targeted panel with error-correction (Lucence Diagnostics) was used to detect for mtin KRAS, TP53, SMAD4, CDKN2A, CTNNB1, GNAS, APC and MYC. CT scans were performed every 2 cycles. Survival curves by Kaplan Meier were compared by mutational status, ctDNA and CA19-9 response using the log-rank test. Spearman correlation of ctDNA and CA19-9 changes was performed. Results: ctDNA mtwas detected at baseline in 19/23 (83%) samples, comprising KRAS 17/23 (73%), TP53 (61%), SMAD4 (48%) and CDKN2A (30%). KRAS mtand SMAD4 mt conferred a negative prognosis for overall survival with a hazard ratio of 4.2 (CI: 1.6-10.4; p = 0.01) and 2.8 (CI: 0.9-8.65; p = 0.01) respectively. Drop in ctDNA and CA19-9 was associated with a trend for longer progression free survival at C2D1 (both) and C3D1 (ctDNA only). Radiological partial response (PR) was associated with lower ctDNA in 5/5 pt and CA 19-9 in 4/5 pt. Decrease in ctDNA and CA19-9 was associated with disease control (PR/SD) at C2D1 in 11/14 pt and 10/10 pt; at C3D1 in 11/12 pt and 6/7 respectively. No significant correlation between the amplitude of CA19-9 and ctDNA changes was found. Conclusions: ctDNA could be detected in 83% of pts of whom KRAS mtrates were similar to reports using tissue NGS. Determination of RAS mtand SMAD4 mtin ctDNA may aid in the prognostication of pts and decrease in ctDNA levels may predict for treatment benefit, similar in extent to CA 19-9. This may be particularly useful in non-CA19-9 secreting APC as an adjunct to imaging. Clinical trial information: NCT02368860.

PURPOSE Precision oncology has transformed the management of advanced cancers through implementation of advanced molecular profiling technologies to identify increasingly defined subsets of patients and match them to appropriate therapy. We report outcomes of a prospective molecular profiling study in a high-volume Asian tertiary cancer center. PATIENTS AND METHODS Patients with advanced cancer were enrolled onto a prospective protocol for genomic profiling, the Individualized Molecular Profiling for Allocation to Clinical Trials Singapore study, at the National Cancer Center Singapore. Primary objective was to identify molecular biomarkers in patient's tumors for allocation to clinical trials. The study commenced in February 2012 and is ongoing, with the results of all patients who underwent multiplex next-generation sequencing (NGS) testing until December 2018 presented here. The results were discussed at a molecular tumor board where recommendations for allocation to biomarker-directed trials or targeted therapies were made. RESULTS One thousand fifteen patients were enrolled with a median age of 58 years (range 20-83 years). Most common tumor types were lung adenocarcinoma (26%), colorectal cancer (15%), and breast cancer (12%). A total of 1,064 NGS assays were performed, on fresh tumor tissue for 369 (35%) and archival tumor tissue for 687 (65%) assays. TP53 (39%) alterations were most common, followed by EGFR (21%), KRAS (14%), and PIK3CA (10%). Of 405 NGS assays with potentially actionable alterations, 111 (27%) were allocated to a clinical trial after molecular tumor board and 20 (4.9%) were enrolled on a molecularly matched clinical trial. Gene fusions were detected in 23 of 311 (7%) patients tested, including rare fusions in new tumor types and known fusions in rare tumors. CONCLUSION Individualized Molecular Profiling for Allocation to Clinical Trials Singapore demonstrates the feasibility of a prospective broad molecular profiling program in an Asian tertiary cancer center, with the ability to develop and adapt to a dynamic landscape of precision oncology.