The management of patients with uterine leiomyosarcomas poses many difficulties. Despite 60% of women present with disease limited to the uterus, cure rates range from 20 to 60%. Patients with metastatic disease at diagnosis or who recur after initial treatment have a dismal prognosis and, except for a subset of selected patients with completely resectable disease, the median survival is less than one year. Treatment options for recurrent/metastatic uterine leiomyosarcoma are limited. The most active drugs are doxorubicin ± ifosfamide and gemcitabine + docetaxel (GD) with response rate of 25-55% and 27-53%, respectively. Both these regimens have been increasingly used in the last years also in the adjuvant setting. For relapsed patients other drugs have been tested as single agent but negligible activity was observed.

Trabectedin (Yondelis® -T) is a marine-derived cytotoxic approved by EMEA. It is indicated for the treatment of patients with advanced soft tissue sarcoma, after failure of anthracyclines and ifosfamide or who are unsuitable to receive these agents. Among STS, activity has been mainly detected in synovial sarcoma, liposarcoma and leiomyosarcoma. Although the response rate did not exceed 10%, T was demonstrated to provide disease control, with progression arrest rates exceeding 50% and progression-free survival rates exceeding 20% at 6 months. So far no phase II studies tested the activity of T in uterine leiomyosarcoma specifically. This study is aimed at evaluating the activity of T (arm A) in advanced uterine leiomyosarcomas, having GD (arm B) as an internal control In parallel translational studies will be performed to identify factors predictive of the activity of T in this specific histotype.

Inclusion Criteria:

1. Histologically proven uterine leiomyosarcoma.
2. Persistent or locally relapsed and/or metastatic disease.
3. At least one previous systemic treatment with an anthracycline ± ifosfamide or gemcitabine ± docetaxel.
4. Measurable disease, as defined by RECIST criteria.
5. ECOG PS <=2.
6. Age >= 18 years.
7. A minimum of 3 weeks since prior tumor directed therapy
8. Recovery from toxic effects of prior therapies to NCI CTC Grade 1 or lower.
9. Adequate haematological function.
10. Adequate renal function.
11. Adequate liver function.
12. Signed informed consent.

Exclusion Criteria:

1. Prior exposure to Trabectedin.
2. Peripheral neuropathy, Grade 2 or higher.
3. History of other malignancies (except basal cell carcinoma or cervical carcinoma in situ, adequately treated), unless in remission from 5 years or more and judged of negligible potential of relapse.
4. Known CNS metastases.
5. Active viral hepatitis or chronic liver disease.
6. Unstable cardiac condition, including congestive heart failure or angina pectoris, myocardial infarction within one year before enrolment, uncontrolled arterial hypertension or arrhythmias.
7. Active major infection.
8. Other serious concomitant illnesses