ECP 2023 Abstracts

S49 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 surgery, chemotherapy, radiotherapy & palliative care. This study aims to review the clinicopathologic features & outcomes in a resource- constrained setting of LMICs. Methods: Hospital-based retrospective analysis of all cases of primary renal Ewing sarcoma/PNET registered between 2014 & 2022. Results: A total of eight patients were identified, of which 4 [50%] were males & 4 females, and the median age: 19.5 years [Range, 12-59 years]. The most common presenting complaint: Haematuria [87.5%], flank pain [62.5%], abdominal mass [25%]. The median tumour size: 9.65 cm [Range, 4.7-31 cm] with RV involvement identified in 3 [37.5%] & IVC in a single case. 75% were non-metastatic at presenta- tion. Upfront nephrectomy: 5 [62.5%] cases. Tumour cells were immu- nopositive for NKX2.2, CD99, FLI1 & synaptophysin. Cytogenetic analysis for EWSR1 translocation: 4 cases. The chemotherapy used a combination of 3-weekly ifosfamide, and etoposide, alternating with vincristine, doxorubicin/dactinomycin, cyclophosphamide. All patients received neoadjuvant/adjuvant chemotherapy & local site radiotherapy in one case. On the last follow up 3 patients [37.5%] were alive with progressive disease, 3 succumbed to metastatic disease, one alive with stable disease, one lost to follow-up. Conclusion: Primary renal Ewing sarcoma carries a guarded prognosis and warrants an aggressive multimodal approach. The diagnosis & management needs to be tailored & modified for every individual and resource-constrained setting. OFP-13 | Joint Oral Free Paper Session Molecular Pathology / Haematopathology OFP-13-001 Comprehensive genomic profiling for precision oncology: the Bel- gian Approach for Local Laboratory Extensive Tumour Testing study (BALLETT) B. Maes*, F. Dedeurwaerdere, I. Vanden Bempt, J. Van Huysse, S. Rottey, J. Vermeij, S. Lambin, J. Van der Meulen, F. Vaeyens, G. Beniuga, K. Punie, C. Van Marcke, D. Schröder, G. Froyen, P. Aftimos *Jessa Hospital Hasselt, Belgium Background & objectives: Comprehensive Genomic Profiling (CGP) in cancer diagnostics is gaining interest but broad access is still limited. The nationwide BALLETT study aims to have a fully standardized CGP analysis available, potentially increasing access to innovative drugs for Belgian cancer patients. Methods: BALLETT is recruiting about 900 patients with a metastatic solid tumour in 12 Belgian hospitals. CGP is weekly performed on pooled samples using the TSO500® kit (Illumina) by one of the 9 hospital labs collaborating in the BALLETT lab consortium. Results are discussed weekly in a virtual, national Molecular Tumour Board (nMTB) resulting in CGP-based treatment recommendations. Results: Since June 2021, tumour samples of 630 patients with 32 differ- ent tumour types have been successfully tested by CGP, with a final test success rate of 94 %. Median turnaround time from informed consent to nMTB discussion was 25 days. For the 30 tumour types with more than 1 case, actionable genomic alterations were recorded in 55 % to 100 % of cases. The nMTB discussions resulted in a CGP-guided treatment recommendation in 441 patients (70 %): reimbursed treatments (n=46), participation to a clinical trial (n=355) or a medical need program (n=8) or off-label drug use (n=32). Follow-up on potential hereditary cancer predisposition was recommended for 74 patients (11,7 %). Conclusion: BALLETT has resulted in a broad access to CGP for patients with metastatic cancer in Belgium. Clinically relevant bio- markers were identified, and CGP-based treatment recommendations were made for the large majority of patients. The uptake of these treatment recommendations and the outcome of the patients will be followed up within the project. Furthermore, the BALLETT labora- tory consortium combined with the nMTB is a valuable platform for reducing turnaround time, exchanging expertise and standardization of CGP methodology and treatment recommendation. ClinicalTrials. gov:NCT05058937 Funding: European Union (CAN.HEAL grant) Belgian Society of Medical Oncologists OFP-13-002 Molecular profiling of advanced urothelial carcinoma in Ireland through next generation sequencing J. Maguire*, S. McCarron, A. Dunne, R. McDermott, C. O’Brien, S. Finn *Histopathology Department, St James’s Hospital, Dublin, Ireland Background & objectives: Mutational burden of urothelial carcinoma (UC) is variable and complex, with therapeutic targets for certain molec- ular alterations (eg. FGFR3). Our aim was to describe the molecular pro- file of UC in our centre with a focus on the occurrence of co-mutations. Methods: All cases of UC that were referred for Next Generation Sequencing (NGS) analysis since its commencement in our centre (December 2021–March 2023) were drawn from the Cancer Molecular Diagnostics Laboratory database (n=77), and the molecular profile of each tumour was analysed using the OncomineTM Focus targeted NGS panel, comprising common driver mutations and oncogenic fusions. Results: As expected, FGFR3 mutations (all variants of strong clinical significance) and fusions (FGFR3::TACC3) were most commonly identi- fied (15% of cases). No FGFR1/2 mutations were identified. All remaining mutations were of potential/unknown clinical significance. PIK3CAmuta- tions were identified in 13% of cases, ERBB2 in 8%, KRAS 6%, CTNNB1 3%, KIT 3% and EGFR in 1%. 4 cases had more than one gene implicated in mutational pathways; MAP2K1/HRAS (both potentially clinically sig- nificant), FGFR3 with a potentially clinically significant PIK3CAmutation, KRAS/KIT mutation of unknown clinical significance and finally one case with 3 mutations PIK3CA, ERBB2 and KIT. 7% of cases were insufficient for analysis, 56% had no mutation identified by this panel. Conclusion: While the identification of 11 cases of UC with FGFR3 alterations is in keeping with published research and of potential thera- peutic benefit, this study also supports the evidence of a spectrum of other genetic mutations of potential clinical significance, includ- ing co-mutations, most notably PIK3CA and ERBB2. The location of the mutations identified in our study is in keeping with The Cancer Genome Atlas (TCGA) findings and suggestive of APOBEC mutagenic activity, potentially predictive of prognosis and therapeutic response. OFP-13-003 Predicting survival from whole-slide images in lung cancer patients treated with immune checkpoint inhibitors M. Ilié*, P. Tourniaire, J. Mazières, A. Vigier, F. Ghiringhelli, N. Piton, J. Sabourin, F. Bibeau, N. Ayache, P. Hofman, H. Delingette *CHU Nice LPCE, Pavillon J, France Background & objectives: PD-L1 expression is currently the only approved biomarker for the selection of NSCLC patients for treatment with immune checkpoint inhibitors (ICIs). However, it lacks both effi- ciency and robustness. We aimed to construct a new solely based on whole-slide image analysis. Methods: First, we used a clustering method based on a deep learning model to cluster patches within the images. After the clustering step, for each slide, we measured the interactions between clusters by count- ing the occurrence of neighbouring patches. Finally, these interaction measures were used to train a Cox Proportional Hazard (PH) model to predict patient overall survival. Results: 149 NSCLC patients from five centres were included in the study. A 5-fold cross-validation of the Cox PH model using PD-L1 expression alone yielded a mean c-index of 0.617 (0.558, 0.676). No statistically sig- nificant difference between low- and high-risk groups was found (HR=1.46,