Epithelioid Sarcoma—From Genetics to Clinical Practice

Epithelioid sarcoma is a mesenchymal soft tissue sarcoma often arising in the extremities, usually in young adults with a pick of incidence at 35 years of age. Epithelioid sarcoma (ES) is characterized by the loss of SMARCB1/INI1 (integrase interactor 1) or other proteins of the SWI/SNF complex. Two distinct types, proximal and distal, with varying biology and treatment outcomes, are distinguished. ES is known for aggressive behavior, including a high recurrence rate and regional lymph node metastases. An optimal long-term management strategy is still to be defined. The best treatment of localized ES is wide surgical resection. Neo-adjuvant or adjuvant radiotherapy may be recommended, as it reduces the local recurrence rate. Sentinel lymph node biopsy should be considered in ES patients. Patients with metastatic ES have a poor prognosis with an expected median overall survival of about a year. Doxorubicin-based regimens are recommended for advanced ES. Tazemetostat, an EZH2 methyltransferase, has shown promising results in ES patients. Novel therapies, including immunotherapy, are still needed.

Phase I study of tazemetostat, an enhancer of zeste homolog-2 inhibitor, in pediatric pts with relapsed/refractory integrase interactor 1-negative tumors.

10525 Background: Absence of integrase interactor 1 (INI1) expression is a defining molecular feature of rhabdoid tumors (RT), epithelioid sarcoma (ES), and chordomas, inducing dependence on enhancer of zeste homolog-2 (EZH2). Tazemetostat (TAZ) is a selective EZH2 inhibitor approved by the FDA for treatment of patients (pts) ≥16 yrs with metastatic or locally advanced ES ineligible for complete resection. Data from a Phase 1 (Ph1) pediatric dose-escalation study (Ph1a) of TAZ were previously reported; herein we report interim efficacy and safety from the Ph1 pediatric dose-expansion study (Ph1b). Methods: NCT02601937 is a Ph1, multicenter study in pts 6 months – 18 yrs evaluating TAZ administered BID at 1200 mg/m2 in Ph1b, per Ph1a recommendation. Ph1b cohorts enrolled pts based on tumor type: Atypical teratoid RT (ATRT), RT, and other INI1-negative tumors (including ES and chordoma). The Ph1b primary endpoint was overall response rate (ORR). Secondary endpoints included safety/tolerability, duration of response (DOR), and survival. Results: Ph1b has enrolled 47 pts who received TAZ oral suspension. Across all tumor types, ORR was 17% (Table). Responses were observed in ATRT (4/21), chordoma (2/4), and ES (2/7); 1 pt dosed at 520mg/m2 and 7pts at 1200mg/m2. In the ATRT cohort, 19% of pts responded to TAZ with a median DOR of 6.5 months. The median DOR has not yet been reached in the other cohorts, with ongoing responses in 3 pts. TAZ was generally well tolerated with no drug-related deaths. Most common adverse events (AE) include vomiting, nausea, and cough. During Ph1b enrollment, 1 pt with chordoma (dosed at TAZ 900 mg/m2 for 15 months in Ph1a) developed a secondary malignancy (T-cell lymphoblastic lymphoma). In response, the pediatric recommended Ph2 dose was revised to limit exposure in pts without CNS involvement to 520 mg/m2 TAZ (maximum dosing of 1 yr after response, pts to go off-treatment until disease progression). Conclusions: Interim results indicate TAZ is generally well tolerated in children with an AE profile similar to adults. Pt enrollment in the non-ATRT, INI1-negative cohorts is ongoing. TAZ shows promising anti-tumor activity in a subset of pediatric tumors, including ATRT, chordoma, and ES. Clinical trial information: NCT02601937. [Table: see text]

Loss of Integrase Interactor 1 (INI1) Expression in a Subset of Differentiated Thyroid Cancer

Alterations in the switching defective/sucrose non-fermenting (SWI/SNF) chromatin-remodeling complex are enriched in advanced thyroid cancer. Integrase interactor 1 (INI1), encoded by the SMARCB1 gene on the long arm of chromosome 22, is one of the core subunits of the SWI/SNF complex. INI1 immunohistochemistry is frequently used for the diagnosis of malignant rhabdoid neoplasms. In the present study, we found normal and benign thyroid tissues generally had diffusely intense nuclear immunostaining. Loss of INI1 immunohistochemical expression was observed in 8% of papillary thyroid cancer and 30% of follicular thyroid cancer. Furthermore, loss of INI1 expression was associated with extrathyroidal extension (p < 0.001) and lymph node metastasis (p = 0.038). Analysis of The Cancer Genome Atlas database revealed that SMARCB1 underexpression was associated with the follicular variant subtype and aneuploidy in papillary thyroid cancer. We speculate that SMARCB1 is an important effector in addition to NF2 and CHEK2 inactivation among thyroid cancers with chromosome 22q loss.

Atypical teratoid/rhabdoid tumor presenting with subarachnoid and intraventricular hemorrhage

Background: Sellar masses comprise 14–18% of all intracranial tumors. Pituitary adenomas account for 85% of these lesions, while 15% of sellar masses stem from other etiologies. Intratumoral hemorrhage (apoplexy), while not exceptionally common, can be discovered at presentation. While the hemorrhage pattern is typically contained within the tumor, an extension of bleeding beyond the sella has been reported. Case Description: A 55-year-old female presented with an anterior interhemispheric subarachnoid hemorrhage and extensive intraventricular hemorrhage (IVH). Initially, the IVH was thought to be due to a ruptured aneurysm. After further workup, a hemorrhagic sellar mass was diagnosed. The patient underwent transsphenoidal resection of a pituitary adenoma. The patient returned to the emergency department6 weeks later with an atypical rapidly expanding sellar mass. After tumor debulking, the pathology revealed an atypical teratoid/rhabdoid tumor (ATRT). Here, we reviewed this and other such cases of sellar ATRT. Conclusion: The early diagnosis of sellar ATRT with lack of integrase interactor 1 expression and elevated Ki67 proliferation indices can prompt more aggressive attempted gross total resection, chemotherapy, and radiation treatments.