(P 222) EXPLORING THE IMPACT OF NGS ON DIAGNOSTICS AND TREATMENT OF SARCOMA: INSIGHTS FROM REAL-WORLD DATA ACROSS MULTIPLE INSTITUTIONS IN EUROPE

Objective: The role of next-generation sequencing (NGS) is still a matter of debate in patients with sarcoma, given the biological peculiarities such as the low mutational burden and the lack of clonal, recurrent, and/or targetable alterations in most of the sarcoma entities. This retrospective, international, and multicenter study aimed to evaluate the clinical importance of NGS for diagnosis and therapeutics of sarcomas in a real-world European scenario.
The primary focus of this investigation was on the application of NGS technologies in the context of subtypes of sarcoma, with specific attention given to their diagnostic utility. Subsequently, the impact of NGS on diagnostic assessment was thoroughly examined. Secondly, this study was also designed to elucidate the usefulness of NGS for identifying actionable mutations in patients with sarcoma, thus improving the prospects of targeted therapeutic interventions in the field of sarcoma therapeutics, which remains controversial. The main objectives of the current study are to determine/quantify the percentage of patients who share specific mutations, the exact subtypes of sarcomas in which targetable mutations are detected and the clinical benefit of those who received targeted therapy.

Methods: Five sarcoma expert institutions from Greece (n=2), Poland (n=1), and Spain (n = 2) participated in this study to reflect the inherent variability between countries and between institutions. DNA and RNA for NGS from bone and soft tissue sarcomas were isolated from formalin-fixed paraffin-embedded tumor tissues. The NGS test was selected at the discretion of the referring physicians in each center. Several diagnostic and/or therapeutic NGS panels were used in all centers participating in this study, including FoundationOneCDx, FusionPlex Sarcoma and Sarcoma v2 panels, and FusionPlex Comprehensive Thyroid and Lung Kit. The relevant patients' demographic and clinical data were recovered from the medical records for descriptive purposes and for correlation with the NGS results. All statistical analyses were performed using R version 4.2.3.

Results: We analyzed a total of 696 patients. The cohort's median age was 47 years (0-89). 379 (54.4%) of the cases were male, and 308 (44.2%) were female. NGS was performed predominantly at the localized stage of the disease (n=406, 58.3%) rather than in metastatic cases (n=267, 38.4%) (Table 1). The most common subtypes that underwent NGS were leiomyosarcomas (n=62), Ewing sarcomas (n=53), and undifferentiated pleomorphic sarcomas (n=51 cases) (Table 2).
Genetic aberrations were found in nearly half of the cohort (n=333, 47.8%). In total, 521 genetic alterations of any type were found in these 333 patients: 274 (52.6%) were mutations, 175 (33.6%) were fusions and 72 (13.8%) gene amplifications. The most frequent findings were as follows: mutations affecting TP53 (n=40), RB1(n = 13) and PIK3CA (n=11); fusions involved EWSR1-FLI1 (n=20), NAB2-STAT6 (n=15), and CIC-DUX4 (n=12); and amplifications of MDM2 (n=9) and CDK4 (n=8).
For the 510 cases in which NGS was performed for diagnostic purposes, 63 (9.1%) resulted in a change from the original diagnosis based on the genetic testing results. CIC-rearranged sarcomas (n=7) and solitary fibrous tumor (n=5) were the most common new diagnoses, followed by PEComas (n=4), Ewing sarcomas (n=4),NTRK-rearranged sarcomas (n=3), and clear cell sarcomas(n = 3).(Table 3).
Ofthe 333 patients with at least one genetic alteration found in the NGS analyses, 136 cases (41% and 19.5% of the entire cohort) had potentially actionable mutations. However, therapies could be administered only in 17 patients, representing 13% of these patients and 2.4% of the entire cohort (Table 4).
Targetable mutations with relevant therapies were detected in 136 cases (19.5%), with only 17 patients (2.4%) receiving targeted therapy.

Conclusion: Various NGS technologies and platforms are increasingly used in oncology centers, primarily for therapeutic indications. Unlike most cancer types, the indication of NGS to provide some aid in diagnosis is paradigmatic in the case of sarcomas, given the pleiad and complexity of the histotypes of sarcomas. On the other hand, the therapeutic options for patients with sarcoma are limited, and NGS testing offers the promise of finding targetable alterations. However, this has been explored mostly in comprehensive cancer centers in the United States, and a clear picture of the more complex reality in Europe is lacking.
Our retrospective study shows that molecular NGS testing can help diagnose sarcomas only in a small proportion of cases (9%). Most of the changed diagnoses could only be made with molecular techniques, as they involved gene rearrangements. Therefore, the prior review of the cases by sarcoma-expert pathologists was key to the need for NGS in this setting.
Our series agrees with previous work that showed a low number of genetic alterations found with NGS, with only half of the patients here harboring at least one. Furthermore, the current study reveals interesting data on the therapeutic impact of NGS in sarcomas. Targetable mutations were detected in 19.5% (136) of patients. However, only 2.4% (17) received appropriate targeted therapy. Thus, the difficulty in obtaining off-label use of alternative drugs significantly limits the potential impact of NGS on the therapeutics and outcomes of sarcomas. Due to the heterogeneity of the population included, it is difficult to conclude the relevance of specific targetable mutations in specific subtypes of sarcomas.
Our results encourage the future generation of an international database collecting actionable NGS mutations detected in sarcoma patients to understand their role in specific subtypes better.