A randomized phase II study of letrozole vs. observation in patients with newly diagnosed uterine leiomyosarcoma (uLMS)

OBJECTIVE: Up to 87% of uterine leiomyosarcomas have estrogen receptor positivity. There are no effective adjuvant therapies for LMS. The objective of this study was to determine the efficacy of letrozole in patients with newly diagnosed uterine leiomyosarcoma (uLMS). The primary endpoint of this study was a reduction in the recurrence rate for patients with this disease. METHODS: We performed a randomized, open-label, phase II study of letrozole (experimental arm) administered orally on a daily basis vs. observation (control) in patients with newly diagnosed early stage uLMS. Patient enrollment was to be open to any individual with newly diagnosed uLMS seen in the Gynecologic Oncology Center at M. D. Anderson Cancer Center. Hormone receptor positivity using CLIA approved lab testing was an eligibility requirement. No prior therapy was allowed. RESULTS: Nine patients were randomized. Four patients were in the experimental arm and five patients were in the observation arm. No patients had prior therapy. The median duration of protocol treatment was 43.9 months (range, 6.5–70.2). The median PFS for the experimental arm was not reached (NR) compared to 17.3 months. The percent progression free at 12 and 24 months was 100% for patients receiving letrozole compared to 80% at 12 months and 40% at 24 months for patients in the observation arm. CONCLUSIONS: While no definitive conclusions can be made due to early study closure, these early observations warrant further investigation. We desperately need an effective adjuvant therapy for women with early stage uLMS.