87P Characteristics and outcomes of 11 patients with myoepithelial tumors: The Gustave Roussy experience

Myoepithelial tumors (MT) constitute a group of ultra-rare soft tissue sarcomas (STS) with unique characteristics. Initial approach is based on optimal surgery but some may exhibit local or distant relapse. There is lack of recommendations regarding the therapeutic approach in this subset of pts. The paper aims to assess the clinical features and outcomes among pts diagnosed with MT. We have performed a retrospective analysis of all pts diagnosed with MT (myoepithelioma (ME) or myoepithelial carcinoma (MC)) at Gustave Roussy from January 2000 until December 2023. Clinical and survival data in addition to response to therapy were gathered from electronic records. 11 pts with MT (4 MC and 7 ME) were included. There were 6 men (54.5%) with a median age of 50.5 yrs (3-71). The most common site of disease were: the upper arm (45.4%) followed by the lower arm (36.4%). All pts had initial localized disease except one with synchronous metastatic MC. The initial approach included surgery in 9 pts followed by adjuvant RT in two pts. One underwent an isolated limb perfusion while no adjuvant chemotherapy were given. After a median DFS of 13.31 mo., 5 pts exhibited a local relapse of whom 3 had metastatic relapse (MR) while 2 pts had prolonged disease remission after local therapy. 3 pts had MR (2 MC and 1 ME), all presenting with lung mets, after almost 4 years of remission. Systemic therapy was administered to 4 pts but no tumor response were recorded across all lines. Pazopanib was most commonly used with 1 stable disease (SD) out of 3 (treated in 2nd or 3rd line). Chemotherapy also showed limited efficacy (1 SD with Paclitaxel and Cisplatine, 1 PD (progressive disease) with oral vinorelbine, 1 PD with oral metronomic cyclophosphamide (met.C). 2 pts were enrolled in clinical trials: 1 had SD with Tazemetostat while another had PD after a combination of a Notch inhibitor and CDK4-6 inhibitor. One pt. had SD with hormone therapy (letrozole) and met.C. MT represent a subgroup of STS with a distinct pattern of disease evolution. This analysis showed a chemo-resistant nature with low sensitivity to commonly used agents in STS. Multicentric data collection with molecular analysis in search of targetable alterations are eagerly needed in this rare entity.