Key result
Ultra-rare sarcomas were associated with worse overall survival compared to non-ultra-rare sarcomas (HR 1.86; 95% CI 1.77-1.96), with age emerging as a major determinant of prognosis.
Why the study?
Ultra-rare sarcomas have an extremely low incidence, resulting in limited clinical understanding.
What are the clinical characteristics, overall survival outcomes, and prognostic factors of ultra-rare sarcomas compared to non-ultra-rare sarcomas?
Cohort (n=1,578,049)
Yes
What are the clinical characteristics, overall survival outcomes, and prognostic factors of ultra-rare sarcomas compared to non-ultra-rare sarcomas?
Effect estimate: HR 1.86 (95% CI 1.77-1.96)
Ultra-rare sarcomas have a rising incidence and worse overall survival compared to non-ultra-rare sarcomas, with age being a major determinant of prognosis.
BACKGROUND: Ultra-rare sarcomas (URSs) are subtypes of sarcomas with an extremely low incidence (≤1 per 1,000,000), resulting in limited clinical understanding. This study aimed to investigate the clinical characteristics, overall survival (OS) outcomes, and prognostic factors of URS by using a national cancer registry database. METHODS: Patients in the Taiwan Cancer Registry, diagnosed between January 2002 and December 2019, were included. Based on ICD-O-3 histologic codes and their incidence, patients were categorized into URS, non-ultra-rare sarcoma (NURS), or non-sarcoma solid tumors (NSST). Annual percentage change (APC) and factors associated with OS were analyzed. RESULTS: Among 1,578,049 patients, 0.23% (n = 3,690) were URS, 1.93% (n = 30,503) NURS, and 97.83% (n = 1,543,856) NSST. The most common URS histologies were conventional chordoma and extraskeletal Ewing sarcoma. The incidence of URS demonstrated an increase from 2002 to 2019 (APC = 2.0), without an improvement in OS (2011-2019 vs 2002-2009 URS: HR, 1.12, 95% CI, 1.02-1.20). After multivariable adjustment, OS remained worse in URS compared with NURS (HR: 1.86, 95% CI: 1.77-1.96). Across all age groups except 0-18 years, URS patients had inferior OS to those with NURS. Notably, within individual URS histologies, age was independently associated with OS. CONCLUSIONS: Despite a rising incidence, outcomes for URSs remain poor. Age emerges as a major determinant of heterogeneity and prognosis, underscoring the need for age-stratified approaches in future research and clinical management. IMPACT: Our findings underscore the urgent need for increased awareness of URS and characterize the impact of age on these patients.
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Lee et al. (2026) conducted a cohort in Ultra-rare sarcomas (n=1,578,049). Ultra-rare sarcoma (URS) vs. Non-ultra-rare sarcoma (NURS) was evaluated on Overall survival (HR 1.86, 95% CI 1.77-1.96). Ultra-rare sarcomas were associated with worse overall survival compared to non-ultra-rare sarcomas (HR 1.86; 95% CI 1.77-1.96), with age emerging as a major determinant of prognosis.
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