(P 150) CLINICAL CHARACTERISTICS OF PRIMARY CUTANEOUS AND SUBCUTANEOUS EWING SARCOMA FAMILY OF TUMORS

Objective: While skin and subcutaneous (cs) primary sites are rare compared to deep or bone primary Ewing sarcoma family tumors (ESFT), the clinical characteristics of these site primary sites remain poorly understood.

Methods: We reviewed clinical data of the ESFT patients treated at our hospital between 2005 and 2019. Our basic treatment strategy included intensive chemotherapy for localized disease (vincristine-doxorubicin-cyclophosphamide/ifosfamide-etoposide administered as a 2-week regimen in pediatric patients and a 3-week regimen in adolescents), followed by definitive surgery with/without radiotherapy. We compared the clinical outcomes of cs-ESFTs with those of ESFTs in other lesions.

Results: In this study, 154 ESFT patients were included, of which 23 patients were cs-ESFT. Among the measurable lesions, the median tumor length was 4.0cm (0.8-11.5cm, in 20 patients). The performance status was 0 in 19 and 1 in 2 patients. Three patients had distant visceral metastasis at the time of diagnosis; the ratio of metastatic ESFTs was significantly lower than ESFTs in other lesions (p< 0.001). Sixteen patients underwent prediagnostic resection with a R0, R1, R2, and an unknown margin status in 1, 10, 3, and 2 patients, respectively (Figure). Of these 16 patients, 3 patients underwent re-resection before induction chemotherapy with confirmation of residual tumor in 2 patients, 11 patients underwent re-resection during planned chemotherapy, and 2 patients with facial lesions underwent concomitant radiotherapy with planned chemotherapy. In the 20 patients with localized type, despite the unplanned procedure performed before diagnosis in many patients, local recurrence did not occurred; however, 3 patients developed distant metastasis. Overall survival was significantly higher in patients with cs-ESFTs than in those with ESFTs in other lesions of the body (hazard ratio [HR]=0.33 [0.13-0.82, 95% CI], p=0.013). Although not statistically significant, the event-free survival rate was superior to other lesions of ESFTs (HR=0.47 [0.14-1.57, 95% CI], p=0.199).

Conclusion: Patients with Cs-ESFTs may have a better prognosis than patients with ESFTs in other lesions. Owing to the rarity of cs-ESFTs, the patients often resected without appropriate procedures or diagnostic imaging. However, local control may be possible using a combination of re-resection or additional radiotherapy.

Ewing抄録図.pdf