Notable Response of SMARCA4-Deficient Undifferentiated Uterine Sarcoma to Palliative Radiation Therapy

Abstract Background : SMARCA4-inactivation induces several malignant tumor types, including the undifferentiated uterine sarcoma, which has recently attracted considerable attention in cancer research. Because this entity is novel, its clinical course and appropriate treatment strategy have not been clarified. Case : A 51-year-old female patient presented with massive bleeding from a uterine tumor. Advanced uterine sarcoma was preoperatively diagnosed based on tumor biopsy findings, and a total hysterectomy and lymph node dissection were performed. The definitive pathological diagnosis of the resected tumor was SMARCA4-deficient undifferentiated sarcoma, which showed monotonous rhabdoid tumor cell proliferation with loss of SMARCA4 expression. The tumor had diffusely invaded the uterine cervix, where the surgical margin was positive. Six courses of doxorubicin and ifosfamide were administrated as adjuvant chemotherapy. The tumor relapsed at the postoperative vaginal stump and right obturator lymph node six months after surgery. Despite several courses of systemic treatment, the locally recurrent lesion and metastasis to the iliac lymph nodes progressed, causing bilateral hydronephrosis and renal dysfunction. Also, the patient experienced abdominal distention and liver enzyme elevation due to multiple liver metastases. Palliative radiotherapy at 8 Gy in a single fraction was administered to each site of recurrence. Radiologically, minor and major tumor shrinkage was observed at the site of local recurrence and liver metastases, respectively. The abdominal symptoms remitted, and the blood test findings, including aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase improved from 57 to 21 U/L, 29 to 17 U/L, and 836 to 407 U/L, respectively. The patient received palliative care and died of the disease 12 months after surgery. Conclusion : The present case is the first to illustrate the response to radiotherapy in SMARCA4-deficient undifferentiated uterine sarcoma. The response to low-dose radiotherapy observed in the present case suggests that radiotherapy may have a place in treatment strategies for this aggressive sarcoma