Leiomyosarcoma of Ovary

Study is aimed at evaluating the activity of Trabectedin (arm A) in advanced leiomyosarcomas, having Gemcitabine (arm B) as the comparator. In addition to the randomized cohort, the study has also an observational prospective cohort which include patients who will refuse the randomization or for whom the investigator will not judge the randomization as an appropriate option. In order to allow the participation of sites only to the prospective-observational (non randomized) cohort, it was introduced the possibility to participate to the study and receive the ethical approval only to the Observational Prospective Cohort In parallel an optional translational study will be performed, in both cohorts, to identify factors predictive of the activity of Trabectedin or Gemcitabine in this specific histotype.