Treatment of hormone positive uterine leiomyosarcoma with aromatase inhibitors

BACKGROUND: Aromatase inhibitors (AIs) have not been used consistently as part of the management of hormone receptor positive uterine leiomyosarcomas (ULMS). As a result, the published data regarding the efficacy of AIs in this subtype of ULMS are sparse. METHODS: We performed a retrospective electronic medical record review of patients with ULMS treated with an AI, in the 1st or the 2nd line setting, at the Sarcoma Unit of the Royal Marsden Hospital between 2001 and 2012. We assessed progression-free survival (PFS), objective response and toxicities and explored the correlation of the intensity of the hormone receptor status, as well as of the grade with PFS. RESULTS: Sixteen patients with measurable advanced ULMS were treated with an AI in our unit. All of them were oestrogen receptor (ER) and progesterone receptor (PgR) positive. Letrozole was used in all patients as 1st line endocrine therapy, while exemestane was mainly prescribed as 2nd line (83%). Median PFS in 1st line was 14 months (95% CI: 0 – 30 months), and prolonged PFS was more likely to be observed in patients with low grade compared to high grade ULMS (20 months vs. 11 months), and in moderately/strongly ER positive compared to weakly ER positive ULMS (20 months vs. 12 months). Best response was partial response (PR) in 2/16 patients (12.5%) and clinical benefit (CB), defined as complete response (CR) + PR + stable disease ≥6 months, was observed in 10/16 patients (CB rate (CBR) 62.5%). Median duration of 2nd line was 3 months and median PFS was not reached. The 1-year progression-free rate for the 2nd line AI was 80%. Best response was PR in one patient and CBR was 50%. AIs were well tolerated in both lines of treatment. CONCLUSIONS: In this population of patients with hormone positive ULMS, AIs achieved a significant CBR (62.5%) in 1st line, which was retained in 2nd line (CBR: 50%). The relatively prolonged median PFS (14 months), along with the favourable toxicity profile could place AIs among the first choices of systemic treatment in hormone positive ULMS, preferably in strongly positive (>90%), and/ or low grade and low volume disease.