Uterine carcinosarcoma: Contemporary clinical summary, molecular updates, and future research opportunity

Uterine carcinosarcoma (UCS) is a biphasic aggressive high-grade endometrial cancer in which the sarcoma element has de-differentiated from the carcinoma element. UCS is considered a rare tumor, but its incidence has gradually increased in recent years (annual percent change from 2000 to 2016 1.7%, 95% confidence interval 1.2-2.2) as has the proportion of UCS among endometrial cancer, exceeding 5% in recent years. UCS typically affects the elderly, but in recent decades patients became younger. Notably, a stage-shift has occurred in recent years with increasing nodal metastasis and decreasing distant metastasis. The concept of sarcoma dominance may be new in UCS, and a sarcomatous element >50% of the uterine tumor is associated with decreased survival. Multimodal treatment is the mainstay of UCS. Lymphadenectomy, chemotherapy, and brachytherapy have increased in the past few decades, but survival outcomes remain dismal: the median survival is less than two years, and the 5-year overall survival rate has not changed in decades (31.9% in 1975 to 33.8% in 2012). Carboplatin/paclitaxel adjuvant chemotherapy improves progression-free survival compared with ifosfamide/paclitaxel, particularly in stages III-IV disease (GOG-261 trial). Twenty-six clinical trials previously examined therapeutic effectiveness in recurrent/metastatic UCS. The median response rate and progression-free survival were 37.5% and 5.9 months, respectively, after first-line therapy, but after later therapies, the outcomes were far worse (5.5% and 1.8 months, respectively). One significant discovery was that epithelial-mesenchymal transition (EMT) plays a pivotal role in the pathogenesis of sarcomatous dedifferentiation in UCS and that heterologous sarcoma is associated with a higher EMT signature compared with homologous sarcoma. Furthermore, next-generation sequencing has revealed that UCS tumors are serous-like and that common somatic mutations include those in TP53, PIK3CA, FBXW7, PTEN, and ARID1A. This contemporary review highlights recent clinical and molecular updates in UCS. A possible therapeutic target of EMT in UCS is also discussed.