Improved outcomes in patients with lymph node-only stage IV disease in clear cell sarcoma: Results from a large single-institution experience and SEER database analysis

Abstract

10571 Background: Clear cell sarcoma, or malignant melanoma of soft parts, is a rare soft tissue tumor unusual among mesenchymal malignancies for its propensity to metastasize to regional lymph node basins. Current AJCC staging for soft tissue sarcoma classifies nodal disease (N1) as stage IV disease. We sought to determine whether patients with lymph node-only disease (N1M0) had better outcomes than patients with distant metastases (M1) by looking at outcomes from both a single institution and population-based data. Methods: Clinical and pathologic factors were retrospectively examined utilizing a prospectively maintained database on patients treated at the University of Texas M.D. Anderson Cancer Center (MDACC) between 1980 and 2007. Histology on all patients was independently reviewed by a single MDACC pathologist with molecular confirmation of the characteristic EWSR1-ATF1 fusion transcript or EWSR1 rearrangement when possible. We also performed a SEER database analysis on patients diagnosed with clear cell sarcoma (1988–2007). Overall and stage-specific disease-specific survival (DSS) were estimated using the methods of Kaplan and Meier. Results: Fifty-three patients with clear cell sarcoma were identified from the MDACC database. Median age at diagnosis was 41 years and 60% were female. Our SEER analysis yielded 130 patients with a median age of diagnosis of 40 years and 54% female. Median follow-up for the MDACC cohort was 7.4 years and median follow-up for SEER was 6 years. MDACC 5-year DSS was 67.9% and, in the SEER analysis, 5-year DSS was 61.9%. The 5 year DSS of N1 patients from MDACC was 74%, while M1 was 14% (p=0.0142). The 5-year DSS of N1 patients from SEER was 52%, while M1 was 0% (p=0.0142). Conclusions: Overall DSS in both our single-institution cohort and in SEER is higher than in previously published series. There is a significant difference in DSS between N1M0 and M1 patients for both MDACC and SEER cohorts. These data underscore the importance of lymph node assessment in these patients and suggest that future staging of clear cell sarcoma should differentiate these groups. No significant financial relationships to disclose.