Abstract 89P
Background
EWSR1::PATZ1 is a rare fusion partnership in sarcoma (sarc). It has been reported in a wide variety of glioneuronal tumors as well as extracranial sarc. Due to the rarity, there are no recommended systemic treatments (tx) to EWSR1::PATZ1 sarc to our knowledge.
Methods
Two patients (pt) harboring EWSR1::PATZ1 are enrolled. Data including pt characteristics, images, histopathological features, molecular testing results, and tx courses were collected.
Results
Case 1: A 51-year-old (yo) woman received curative resection (op) of left frontal tumor, which revealed an IDH wild type glioblastoma/ gliosarcoma (GS) with majority of the tumor cells positive for GFAP, while some high grade areas showing loss of GFAP, ki-67 up to 70%, and increased reticulin stain. She completed radiotherapy with concurrent and adjuvant temozolomide (TMZ) per Stupp protocol. 21-months (mos) after initial diagnosis, she presented with dyspnea for one week. CT scan revealed lung, pleura, bone, and peri-renal cortical tumors as well as mediastinal nodes. Brain MRI showed scalp nodules without intracranial recurrence. Lung tumor biopsy favored metastatic GS, with EWSR1::PATZ1 (Table). She failed bevacizumab (bev) alone or in combination with TMZ. Therefore, BEEP (Bev 15mg/kg D0, etoposide 70/m2 D1-D3, cisplatin 70/m2 D1, Q21D) was given for salvage. CT at 8-weeks showed partial response of lung and pleural tumors. The pt is still alive with ongoing BEEP tx for more than 4 mos. Case 2: A 73 yo woman presented with a right upper back tumor for 1 year. MRI revealed a 6.5cm tumor in the right posterior paraspinal region of T2-5 level. Curative op was done and reported a round cell sarc with EWSR1::PATZ1 (Table). Without any adjuvant tx, she remained disease-free for more than 8 mos till now. Table: 89P
Histopathological and molecular features of the two patients
| Case 1 | Case 2 | |
| Tissue origin | Lung tumor biopsy | Soft tissue tumor op |
| Histology | Small blue round cells with high mitotic activity and tumor necrosis | Epithelioid, round to focally spindle cells, with rare mitosis and no necrosis |
| Immunohistochemical stains | Synaptophysin+ (focal), S100-, GFAP-, desmin-, CK-, TTF-1- | Synaptophysin+ (weak), S100+, GFAP+ (rare), desmin+, MyoD1+ |
| Molecular findings | FoundationOne Heme:EWSR1::PATZ1CDKN2A/B lossPALB2::CLEC16ATumor mutational burden: 7 Muts/ MbMicrosatellite status stable | FISH: EWSR1, FUS, FOXO1, NCOA2 no rearrangement RT-PCR: no EWSR1::PATZ1 Nested RT-PCR: EWSR1::PATZ1 |
Conclusions
EWSR1::PATZ1 sarc can behave very differently. For aggressive ones, BEEP has shown some clinical activity. Conventional FISH or RT-PCR may not be sensitive enough to detect EWSR1::PATZ1. Nested RT-PCR or NGS are better options.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.