(P 334) CHARACTERISTICS AND OUTCOMES FOR PATIENTS IN THE UNITED STATES WITH DEDIFFERENTIATED LIPOSARCOMA FROM A REAL-WORLD DATA SET

Objective: Few epidemiological studies describing patients with dedifferentiated liposarcoma (DDLPS) exist, and real-world outcomes data are limited. This study aimed to characterize patients with metastatic DDLPS and assess effectiveness outcomes among those receiving systemic therapy and next-generation sequencing (NGS) in the United States.

Methods: This observational cohort study used the US-based deidentified Flatiron Health-Foundation Medicine (FH-FMI) Pan-Tumor Clinico-Genomic database, which is linked to approximately 280 cancer centers (~800 sites of care). Key inclusion criteria included adults (aged ≥18 years) diagnosed with chart-confirmed metastatic DDLPS from January 1, 2011, to December 31, 2020, who received NGS testing by FMI and received treatment within 14 days before or at any time after the date of metastatic diagnosis. The study period was January 1, 2011 through December 31, 2021. Patients were followed until death, end of study period, or loss to follow-up, whichever occurred first. The index date was the date of initiation of first-line (1L) treatment. Median overall survival (OS) was the time from the index date to the earliest record of death. Real-world progression-free survival (rwPFS) was the time from the index date to the earliest record of disease progression or death based on each patient’s chart. Patients without records of death or progression were censored at the last activity date before the end of the study period.

Results: Of 52 selected patients with DDLPS, 43 were diagnosed in 2016 or later. The mean (standard deviation [SD]) age at initiation of 1L treatment for patients with DDLPS was 63.3 (12.8) years. Patients were more likely to be male (63.5%), White (73.1%), and have an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 or 1 (61.5%; ECOG PS missing/unknown in 30.8% of patients). Initial stage at diagnosis was missing in 55% of patients. MDM2 amplification (amp), defined as >8 copies, was seen in 76.9% of patients; 13.5% had a TP53 mutation. Mean time between metastasis diagnosis and start of treatment was 4.2 (9.5) months (mo) and 6.5 (4.5) mo for patients receiving 1L and second-line (2L) treatment, respectively. Median number of treatments received was 2 (IQR, 1-3). Treatments are listed in Table 1. The most common 1L treatment was doxorubicin (doxo) with olaratumab (23.5%), followed by gemcitabine and cisplatin (15.7%). Doxo in combination with other therapies was seen in 15 patients. In 2L, eribulin was the most common (21.9%), followed by gemcitabine (15.6%). OS and rwPFS were 12.6 mo (95% CI, 8.3-19.8 mo) and 2.5 mo (95% CI, 2.3-4.1 mo), respectively, for all patients (n=49). In patients with MDM2 amp and wild-type TP53 (n=37), they were 12.6 mo (95% CI, 6.8-38.0 mo) and 2.5 mo (95% CI, 2.2-5.2 mo), respectively. In patients with a TP53 mutation and no MDM2 amp (n=5), they were 31.5 mo (13.8 mo-not available [NA]) and 4.4 mo (95% CI, 4.1 mo-NA), respectively. In 15 patients (any MDM2 status) who received 1L doxo monotherapy or in combination, OS was 16.6 mo (95% CI, 12.6-NA) and rwPFS was 3.6 mo (95% CI, 2.2-13.2 mo).

Conclusion: Patient demographics are consistent with a 2012 report on 208 patients from 11 institutions (10 European members of the Connective Tissue Cancers Network of Excellence and Memorial Sloan Kettering Cancer Center [New York, NY]); however, median OS observed is lower than the reported 15.2 months. For those receiving 1L doxo monotherapy or in combination, rwPFS was comparable to this report and to a 2017 report on 51 patients at MD Anderson Cancer Center (Houston, TX). These results may highlight an awareness gap between academic centers and community practices for treating DDLPS. Potential limitations include that the data may have a selection bias from the limited number of centers during the study period, and data are derived largely from community practices in the United States and only include patients who also received NGS.