Myxoid leiomyosarcoma: A population-based NCDB analysis.

Abstract

e17611 Background: Myxoid leiomyosarcoma is a rare malignant smooth muscle tumor characterized by abundant myxoid stroma and low cellularity. Despite its rarity, it carries a significant clinical burden, with frequent recurrence or metastasis following initial treatment, and may respond differently to chemotherapy and radiation compared to conventional leiomyosarcomas. However, existing evidence is largely derived from small case series and single-institution studies, as the rarity of this cancer has limited population-based analyses examining demographic, clinical, and socioeconomic factors, as well as long-term incidence trends. To address this gap, the National Cancer Database (NCDB) was utilized to examine population-level demographic and clinical characteristics of myxoid leiomyosarcoma. Methods: A retrospective review of cases from the NCDB, between 2004 and 2020, identified 621 individuals with histologically confirmed myxoid leiomyosarcoma (ICD-O-3: 8896). Demographic and socioeconomic characteristics, such as age, sex, race, insurance type, treatment facility, educational level, and Charlson–Deyo comorbidity status, were summarized using descriptive statistical methods. Incidence and survival patterns were evaluated using regression analysis and Kaplan-Meier estimates. Results: The average age at diagnosis was 55 ± 13.2 years. Most patients were female (95.5%), non-Hispanic (89.9%), and White (69.7%). Privately insured patients accounted for 58.8%, with most treated at academic/research institutions (43.6%), followed by comprehensive community (27.4%) and integrated network centers (24.1%). Additionally, 65.3% lived in large metropolitan areas, with a mean distance of 30.1 ± 100.6 miles from the reporting hospital. Primary tumors were most often uterine (C549/C559); 29.1% were stage I and 10.8% stage IV. Tumor sizes ranged 2–400 mm (mean 122.7 mm). Surgery was performed in 92.1% of patients, with 94.7% surviving 90 days; 63% had negative margin resections. Other treatments included radiation (16.3%), chemotherapy (33%), hormone therapy (2.3%), and immunotherapy (0.5%). Long-term survival had 2-, 5-, and 10-year survival rates of 73.4%, 58%, and 47.8%, respectively; overall mean survival was 9.7 ± 0.18 years. Conclusions: This study is the first to address a significant gap in knowledge about myxoid leiomyosarcoma by utilizing a retrospective NCDB analysis. Comparable to existing studies, myxoid leiomyosarcoma is predominant in non-Hispanic female populations. Socioeconomically, the majority of patients come from higher household income quartiles and reside in larger, metropolitan areas. This shows that our cohort aligns with NCDB baseline findings regarding patient demographics for this cancer. Future studies should focus on a better understanding of the impact of demographic and socioeconomic factors on diagnosis, treatment, and overall survival of those with myxoid leiomyosarcoma.