e18035 Background: Uterine leiomyosarcoma (ULMS) is a rare tumor with limited therapeutic options and no clearly established best treatment sequence strategy. Methods: Women with ULMS between 2013-2018 were identified. Clinical data was collected; descriptive statistics were performed and predictors of overall survival (OS) and progression free survival (PFS) were analyzed. Results: 189 patients were included. Median age was 53 (20-84), 91% had grade 3 tumors and 51.3% had stage IB disease. 50% underwent surgery followed by chemotherapy (n = 94, 49.7%) and 37% had surgery only (n = 70). 49 patients retained their ovaries; there was no difference in OS by oophorectomy status (p = 0.71). Estrogen and progesterone receptor (ER/PR) status, positive in 41% and 33% respectively, was not independently associated with OS (p = 0.23, p = 0.12) nor did it impact OS among those with oophorectomy and without (p = 0.70). The most common adjuvant therapy regimens were gemcitabine/docetaxel (gem/doce, 64%) or ifosphamide/doxorubicin (ifos/doxo, 19%). There were no differences in the regimens prescribed by physician specialty (gynecologic oncology vs other, p = 0.21). 147 patients (78%) experienced a recurrence or progression. For the 73 patients who received gem/doce as adjuvant therapy, 58.9% recurred and were most commonly treated with doxo containing regimens (67%). Of the 22 patients treated with ifos/doxo, only 3 recurred and each received a different second line regimen. For those not treated with adjuvant therapy (70 patients), 58.2% recurred and were treated with gem/doce (62%) and ifos/doxo (24%). In early stage patients, the majority received surgery only (45%) or surgery followed by chemotherapy (44%). There was no difference in OS in those who received adjuvant therapy and those who did not (p = 0.39). 46 (24%) had molecular testing and 37 had identified mutations. The most common mutation found was P53 (n = 25, 54%) followed by RB1 (8, 17%), PTEN (7, 15%), and BRCA (2, 4%). Conclusions: Recurrence occurred in 78% of patient despite many women undergoing adjuvant therapy after surgery. Oophorectomy did not influence OS, even though 41% of tumors were ER positive. The sequence of treatment was not associated with OS, however, the risk for recurrence in patient treated with adjuvant Ifos/Doxo was 14% compared to 59% in gem/doce. This finding warrants additional evaluation to determine the optimal adjuvant therapy for these women.
MA23.07 Defining the Role of Adjuvant Therapy for Early Stage Large Cell Neuroendocrine Lung Cancer