(P 132) PATIENT CHARACTERISTICS, TREATMENT PATTERNS AND DISEASE BURDEN OF DEDIFFERENTIATED LIPOSARCOMA IN CHINA: A REAL-WORLD STUDY BASED ON NATIONAL CANCER REGISTRY

Objective: Currently, there is very limited evidence regarding the natural history, patient journey, and treatments of Chinese patients with dedifferentiated liposarcoma (DDLPS). Thus, this study was conducted to describe the characteristics, treatment patterns and disease burden of Chinese DDLPS patients in real-world settings.

Methods: Study design and data source
This was a retrospective, observational study using longitudinal electronic medical records from the National Anti-Tumor Drug Surveillance System (NATDSS), the largest cancer registry in China. Eligible DDLPS patients were identified from January 1, 2013 to December 31, 2021 and were followed from index date until death, end of study period, or loss to follow-up (Figure 1).

Inclusion criteria
•Patient has two or more documented clinical visits in the NATDSS network on or after January 1, 2013.
•Historically confirmed diagnosis of DDLPS.
•At least 18 years old at the date of initial diagnosis.
No exclusion criteria were applied.
The study population was divided into two cohorts based on whether they received systemic therapy or not: Cohort 1 included patients with at least one line of systemic treatment, Cohort 2 included patients without any line of treatment.

Outcomes
•Overall survival (OS) defined as time from start of each systemic treatment line until the earliest record of death or last visit for Cohort 1.
•Survival after initial DDLPS diagnosis for both cohorts.
•Treatment patterns defined as treatment regimens received in each line for Cohort 1.
•Healthcare resource utilization (HCRU) and direct medical cost categorized as inpatient admission and outpatient visit since DDLPS diagnosis for both cohorts.

Results: Study population
This study included 1390 patients (Table 1):
•Cohort 1 included 275 patients: 20 (7.3%) initiated first line (1L) after an unresectable advanced diagnosis, while 255 (92.7%) initiated 1L after a metastatic diagnosis or recurrence. On average, they underwent 1.3 (0-8) surgeries before 1L.
Cohort 2 included 1115 patients without any line of treatment, 615 (55.2%) were metastatic/recurrent patients. On average, they underwent 1.5 (0-9) surgeries after DDLPS diagnosis.

Systemic treatment patterns
In Cohort 1, patients received an average of 1.8 lines of treatment. Among them, 52.4% received only one line, 29.1% received two lines, and 18.6% received three lines or more. The predominant regimen in 1L was anthracycline-based (43.4%), followed by anlotinib-based (30.9%). Similarly, in 2L and 3L the most common regimen was anlotinib-based, with anthracycline-based as the second choice (Table 2). Notably, over 80% of patients initiated their 1L since 2019 when anlotinib was included in national medical insurance catalog, which largely explains its significant adoption across different lines.

Survival from each line and from initial diagnosis
In cohort 1, the median OS was 13.4 (95%CI, 12.4-16.5) months from the start of 1L, 10.8 (95%CI, 9.1-18.1) months from 2L and 7.89 (95%CI, 3.9-NE) months from 3L, respectively (Figure 2).
The median survival from initial DDLPS diagnosis was 35.6 (95%CI, 30.3-41.6) months and 43.9 (95%CI, 41.0-55.1) months for Cohort 1 and 2, respectively.

Healthcare resource utilization (HCRU) and direct medical cost
The median of inpatient admissions in Cohort 1 was 4 (interquartile range (IQR), 2-8), with an average of 9.2 days for each admission. The Cohort 2 patients have a median inpatient admission of 2 (IQR, 1-4), with an average of 16 days for each admission. The median of outpatient visits in Cohort 1 and 2 was 10 (IQR, 4-21) and 6 (IQR, 3-12), respectively.
The total direct medical cost of inpatient admission per patient exceeded 130 thousand Yuan for both cohorts. The cost from outpatient visits in Cohort 1 amounted to 33 thousand Yuan per patient, which is double the cost in Cohort 2.

Conclusion: This study represents the largest cohort of Chinese patients with DDLPS to date, providing comprehensive insights into the current standard of care in real-world settings. The findings highlight the substantial economic and healthcare burden associated with this rare tumor and emphasize the urgent need for targeted therapies for advanced DDLPS.

In Cohort 2, over half of the metastatic/recurrent patients did not receive systemic treatment, which can be attributed to various reasons. Firstly, the inadequate identification of high-risk patients and a lack of understanding of systemic therapy and its benefits contribute to this issue, which need to be addressed and strengthened in clinical practice. Secondly, despite undergoing multiple surgeries, patients have very limited options for systemic treatment. As observed in Cohort 1, the late start of systematic treatment and the notable increase in the use of anlotinib following its approval further underscore the necessity to expand the available means of systematic treatment.