(P 419) AGE ADJUSTED TRENDS IN PATIENTS WITH SYNOVIAL SARCOMA

Objective: Synovial sarcoma is an uncommon malignant tumor that predominantly affects muscles and ligaments. We have a very limited data regarding the trends and incidence rates of this rare type of sarcoma due to its scarcity which lead to controversy in regards of its screening and treatment guidelines. So, this study aims to add more evidence and data about this rare type.

Methods: Data of 2,872 patients was extracted from the Surveillance, Epidemiological, and End Results (SEER) database diagnosed from 2000-2019. The histopathological classification was according to the WHO ICD 0-3. We analyzed Age-Adjusted Trends and Age-adjusted incidence rates. Rates are per 100,000 and age-adjusted to the 2000 US Std Population (19 age groups - Census P25-1130) standard; Confidence intervals are 95% for rates (Tiwari mod) and trends. Percent changes were calculated using 1 year for each end point; APCs were calculated using weighted least squares method. All data are from cases diagnosed between 2000-2019.

Results: The overall incidence rate was 0.17. The age-adjusted trend analysis showed that annual percentage change (APC) was 0.1 (95%CI -0.5 to 0.7) from the year 2000 to 2019 and the percent change (PC) was 5.1. This increase occurred across all ages, races, sexes and subtypes. With stratification by histopathology, NOS, spindle cell, biphasic cell and epithelioid cell synovial sarcoma PCs were -11.5, 108.4, -23.6, and -78.4, respectively and the APCs were 0.1 (95%CI -0.9 to 1.1), 1.0 (95%CI-0.6 to 2.5), -1.6 (95%CI -3.0 to -0.1) and it was missing for epithelioid cell. Males showed higher PC of 11,7 (APC: -0.2 95%CI -1.1 to 0.7) compared to females; -2.0 (APC: 0.4 95%CI -0.5 to 1.3). With stratification by age groups, age groups 0-14, 15-29, 30-44, 45-59 and 60+ showed PCs of -5.9, -18.3, -8.6, 47.5 and 50.6 respectively and APCs of -0.6 (95%CI -3.6 to 2.5), -1.1 (95%CI -2.0 to -0.1), 0.4 (95%CI -0.8 to 1.6), 0.7 (95%CI -0.8 to 2.3) and 0.9 (95%CI -0.9 to 2.6) respectively.

Conclusion: Synovial sarcoma showed an increase in its overall incidence rate. However, with subtyping of Synovial sarcoma, spindle cell subtype showed the main increase while NOS, epithelioid cell and biphasic cell subtypes showed a decline in their incidence rates. Synovial sarcoma showed rising incidence rates in Males while for Females, it was declining. Only age groups over 45 showed an increase in their incidence rates. This increase in the incidence rates of synovial sarcoma warrants the need of the development of screening guidelines. Also, we recommend focusing on males and patients above 45 as they have showed the most rise in their incidence rates.