High-grade surface osteosarcoma: A National Cancer Database study of demographic characteristics.

e23508 Background: High-grade surface osteosarcoma (HGSO) is an extremely rare malignant subtype of osteosarcoma. HGSO often affects long bones, particularly the femur, and is the rarest subtype of surface osteosarcomas. Though data is limited, current information suggests this cancer presents with a poor prognosis, generally affecting adults aged 20 to 40. Current treatment standards involve wide resection and chemotherapy. The National Cancer Database (NCDB) was examined to establish the demographic factors among HGSO patients and identify diagnostic and treatment trends. Methods: A retrospective cohort study from 2005-2020 was conducted using the NCDB. A total of 99 patients were found with a histologically confirmed diagnosis of high-grade surface osteosarcoma (ICD-9194-3). Factors such as gender, age, race, insurance status, rural/urban residence, treatments, mortality rates, and Charles/Deyo scores were analyzed using descriptive statistics, and trends in incidence were interpreted via regression analysis. Results: Yearly HGSO incidence rates increased from 2005 to 2020 (R2 = 0.19). The average age of diagnosis was 41 years (SD = 24.9, range = 10-90) with men diagnosed (54%) slightly more than women. The majority of patients were non-Hispanic white (73%), had private insurance (55%), and lived in a metropolitan area with over 250,000 in population (89%). The average patient was diagnosed at a hospital 40.4 miles away from their home (SD = 84.9, range 0.4-648.4 miles). Most patients (55%) were in stage II at diagnosis, and 86% of patients had a Charlson-Deyo comorbidity score of 0. The most common primary site of this malignancy was the long bones of the lower limb and associated joints (67%), while the upper extremities (8%) and pelvic bone (8%) served as less common primary sites. Surgery was the most common primary treatment (62%). Data from 69 patients revealed the 90-day mortality post-surgery was 3%. The mean survival rate was 70% at two years and 52% at five years. Conclusions: To the best of our knowledge, this study represents the first NCDB analysis of HGSO. Our analysis demonstrated that HGSO occurs most often, but not exclusively, within the lower extremity long bones, which may be an important diagnostic distinction. It was previously indicated that the average age at HGSO diagnosis is 20-40 years, but our analysis suggested it is closer to 40. Our analysis revealed a five-year survival rate of 52% which is worse than prior studies have indicated. Demographic data has revealed the majority of patients were non-Hispanic white, privately insured, and living within a metropolitan area. This trend may suggest access to healthcare resources is influencing this cancer’s diagnosis and treatment. Further research is warranted to explore whether the demographic patterns seen in HGSO are indicative of biological causes or socioeconomic factors that are significantly influencing diagnosis.