Epidemiology and survival analysis of non-GIST GI sarcomas: A two-decade analysis of SEER database.

Abstract

812 Background: Primary adult non-GIST (gastrointestinal stromal tumors) gastrointestinal sarcomas are rare, accounting for 1-2% of all GI malignancies. Given the paucity of literature, we aimed to study the epidemiology and clinical outcomes of these sarcomas. Methods: National SEER-18 registry database was analyzed from 2001 to 2019 to identify non-GIST-GI sarcomas among adults aged 20 years and older. Demographics and clinical factors, including age at diagnosis, gender, race, primary cancer site, histology group, tumor grade and treatment, were examined in descriptive analysis. Log-rank tests, KM plots and Cox regression were utilized for observed survival analysis. P-value of <0.01 was considered statistically significant. Retroperitoneal sarcomas were excluded. Results: A total of 1277 non-GIST-GI sarcomas were identified, 53.6% were male. Common primary sites include small intestine (32.4%), stomach (27.0%), colon (23.0%), esophagus (8.4%), rectum (8.3%) and anus (0.9%). Most common histological subtype was leiomyosarcoma (52.8%) followed by sarcomatoid carcinoma (10.6%), spindle cell sarcoma (6.2%), carcinosarcoma (5.9%), liposarcoma (5.2%) and angiosarcoma (4.7%). Surgery only was the most common treatment received (61.4%). Stratified by primary tumor site, five-year survival rate was highest for colon (46%; 95% CI 40-52) followed by anus (HR 44%; 95% CI 15-70), stomach (HR 42%; 95% CI 36-47), rectum (HR 36%; 95% CI 27-46), small intestine (HR 36%; 95% CI 31-41) and esophagus (HR 30%; 95% CI 21-38).Similarly, for common histological subtypes 5-year survival was highest for liposarcoma (HR 56%; 95% CI 43-68) followed by leiomyosarcoma (HR 46%; 95% CI 42-50) and spindle cell sarcoma (HR 36%; 95% CI 25-47) and lowest for carcinosarcoma (HR 15%; 95% CI 8-25) followed by sarcomatoid carcinoma (HR 17%; 95% CI 11-24), and angiosarcoma (HR 17%; 95% CI 9-28).On multivariate cox regression analysis, factors associated with unfavorable prognosis were male gender (HR 1.21; 95% CI 1.06-1.39), small intestine (HR 1.38; 95% CI 1.15-1.65) sarcomatoid sarcoma (HR 1.42; 95% CI 1.06-1.92), poorly differentiated tumors(HR 2.90; 95% CI 1.99-2.43). Esophageal primary (HR 0.66; 95% CI 0.49-0.87) and leiomyosarcoma (HR 0.81; 95% CI 0.70-0.94) had a favorable prognosis. Conclusions: Non-GIST-GI sarcomas are very rare with slight male predominance and more than three quarters of cases diagnosed among 55 years and older. Leiomyosarcoma was the most common subtype and small intestine was most common primary site. Overall liposarcoma had the highest five year survival rate and carcinosarcoma had the lowest.On multivariate analysis male gender, small intestinal primary, sarcomatoid carcinoma had unfavorable prognosis.