75P Review of the systemic treatment of leiomyosarcomas in a Spanish reference center in the last 10 years

Leiomyosarcomas (LMS) belong to the group of soft tissue sarcomas (STS) and are one of the most common subtypes, along with liposarcoma (LPS). In the initial stages the gold standard treatment is based on surgery, while the role of chemotherapy (CT) is reserved for advanced stages, although its use has also been studied in the adjuvant and neoadjuvant context, with not enough evidence to support its use in these context. First-line treatment include doxorubicin in monotherapy or in association with other active agents such as gemcitabine, dacarbazine and trabectedin. Other molecules can be used for further lines such as hormone treatment, pazopanib and others. We conducted a retrospective, longitudinal and observational study. We reviewed a total of 50 patients with LMS who have received treatment with CT either in the context of adjuvant or metastatic disease. The data was analyzed using the free statistics software Jamovi, using non-parametrical tests for variable associations and frequency measurements for descriptive analysis. Regarding adjuvant treatment, a total of 26 cases were analyzed, and the relapse rate was 57.6%. Not affected surgical margins was the only factor associated with better OS (50 vs 23 months, p value= 0.005) and RFS (12 vs 3, p value= 0.039). Of the 34 patients with metastatic disease analyzed. Main findings of different regimens and agents of RR, median OF and median PFS are shown in the table.Table: 75PChemotherapyOR (%)p valuemedian OS (months)p valuemedian PFS (months)p valueFirst line: Adriamicine vs gemcitabine86 vs 500.0736 vs 160.556 vs 40.96Second line: Gemcitabine vs trabectedin66 vs 571.0011 vs 90.669 vs 50.1Subsequent lines: Gemcitabine Trabectedine Pazopanib66 33.3 50- - -9 6.5 4- - -6.5 3.5 3- - - Open table in a new tab The only factor that was associated with better RFS and OS in patients who received adjuvant treatment with CT was the presence of free surgical margins. First-line treatment with CT in patients with metastatic disease with regimens based on doxorubicin showed more activity compared with others such as gemcitabine, trabectedin, but no statistically significant differences were found. We consider that any of these three agents can be used for patients with metastatic disease.