(P 133) REAL-WORLD ANALYSIS OF DEDIFFERENTIATED LIPOSARCOMA (DDLPS) IN A US COMMUNITY ONCOLOGY SETTING

Objective: Dedifferentiated liposarcoma (DDLPS), an aggressive adipocytic tumor subtype, most often exhibits substantial mouse double minute 2 (MDM2) amplification. Its clinical care involves a multidisciplinary team of surgical, medical, and radiation oncologists, as well as pathologists, occurring in academic centers or community oncology practices. However, due to limited real-world evidence, it is crucial to examine DDLPS diagnosis and clinical care in community settings to understand opportunities for enhancing clinical outcomes. This study presents demographic and clinical characteristics of patients with DDLPS from a real-world US community oncology setting.

Methods: Patients age ≥18 years and diagnosed with DDLPS (any stage) between Jan 1, 2008, and Oct 31, 2023, within the US Oncology Network and non-Network practices (independent community-based oncology clinics in partnership with Ontada) were eligible for inclusion. Patients were followed through date of death or last available record on or before Oct 31, 2023 (whichever came first). Data from the iKnowMed electronic health record system were analyzed, with the first documented DDLPS diagnosis date as the index; for biomarker testing data, if patients had multiple records, the data closest to the index date were used (except for tests per patient rate). Descriptive statistical analyses were conducted.

Results: Key demographics and clinical characteristics for 123 patients with DDLPS at any time in the study period are in the Table. The mean (SD) age at index was 66.1 (11.5) years, and most patients were White/Caucasian (60.2%; n=74) and/or men (66.7%; n=82). The median (range) follow-up time was 16.7 (0.5-130.5) months. Initial sarcoma diagnosis based on patient disease histology was predominantly DDLPS (82.9%; n=102). Among 21 patients with initial sarcoma diagnosis, median (range) time to index DDLPS diagnosis was 1.6 (0.1-171.5) months. Almost half of patients had tumors located in the retroperitoneum (48.8%; n=60) followed by abdomen (18.7%; n=23). Fifteen (12.2%) patients had metastatic status (stage IV) at initial diagnosis. The lung was the most frequent distant metastatic site (18.7%; n=23). Overall, 118 biomarker tests with MDM2 were administered to 96 patients (78.0% testing rate), with a mean (SD) of 1.2 (0.5) tests per patient; positive/amplified results, as defined by the assay, were detected in 95 patients (negative result in 1 patient). Additionally, 13 biomarker tests with tumor protein P53 (TP53) were administered to 13 patients (10.6% testing rate; 11 were negative/no pathogenic mutation detected; 1 was positive/pathogenic mutation detected; 1 was indeterminate), and 52 biomarker tests with cyclin-dependent kinase 4 (CDK4) tests were administered to 47 patients (38.2% testing rate; 40 had amplified/positive results; 6 were not amplified; 1 was indeterminate).

Conclusion: Findings from this real-world analysis of patients with DDLPS from the US Oncology Network and non-Network highlights several key points. DDLPS presentation was heterogeneous. Most patients received an initial diagnosis of advanced localized DDLPS with a smaller proportion with metastatic disease. Both situations pose opportunities for improved systemic therapy as surgery often is not curative in locally advanced and metastatic presentations. Most patients in the present study received MDM2 testing, whereas fewer patients received TP53 or CDK4 testing; these observations highlight a broad need for improving biomarker testing (specifically for TP53 and CDK4). Together, these findings shed light on the patterns of diagnosis and molecular testing of patients with DDLPS at community oncology sites.