Prognostic and predictive factors for the outcomes of clear cell sarcoma (CCS) multidisciplinary treatment: The role of lymph node involvement.

Abstract

e23554 Background: CCS is a rare aggressive sarcoma with melanocytic differentiation and specific genetic background of EWSR1/ATF1 or EWSR1/CREB1 translocations. It typically localizes in the tendons, fascia, and aponeuroses. The role of lymph node dissection (LND) remains to be elucidated in this sarcoma, although it was indicated to have a high rate of clinically occult regional lymph node (LN) metastases. Methods: 23 consecutive patients (pts) (15 women and 8 men) were referred, diagnosed and underwent multidisciplinary treatment in our Institute between 07/2000 and 12/2019. Kaplan-Meier estimator was used in survival analysis and univariate Cox proportional hazard model was used to investigate prognostic and predictive factors. Cases for whom local relapsed were not noted or those not known to be dead were censored at last visit. OS was compared for nodal involvement, including both: clinically detected and treated with therapeutic LND and microscopic metastases evaluated in sentinel LN biopsy (SLNB). Local relapse and radiotherapy were analyzed. Results: The median age at diagnosis was 32y (range:20-72). The median tumor size was 3.5cm (2-15cm). 15 pts underwent surgery of the primary tumor and 8 - resection of local relapse after non-complete resection outside the reference center. In 11 cases SNLB was performed, while in 7 – therapeutic LND. SLNB was positive in 2 (18%) cases and was followed by completion LND. For pts treated due to primary tumor, R0 resection was achieved in 12 cases and R1 in 3. After median follow-up of 65.6 months (m) (95% confidence interval, CI 55.3–NR) 11 (48%) pts are alive. Median OS was 59m (95%CI: 39-NR). Clinically detectable LN were correlated with shorter DFS (HR: 6.6, 95%CI: 1.5-28.8, p = 0.01). The number of involved LN also correlated with DFS (HR 1.7 per 1 LN; 95%CI:1.1-2.6, p = 0.009). No such correlations were found for OS. 5-year LRFS rate was 72.5% (95%CI: 53.8-97.7). 15 pts underwent neoadjuvant radiotherapy and for these pts 5-year LRFS rate was 75.0% (95%CI: 50.3-100). There was no statistical difference for LRFS if radiation therapy was not applied, which may be due to the number of pts. Conclusions: CCS is a highly aggressive sarcoma with poor prognosis. High quality surgery remains the gold standard for these pts, with the increasing role of SLNB and LND. Multimodal treatment should be considered in all cases. There is unmet need for new therapies for advanced CCS pts.