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Letrozole shows promise in advanced uterine leiomyosarcoma
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Letrozole demonstrated activity in patients with advanced, unresectable uterine leiomyosarcoma, according to the results of a single-arm phase 2 study.
Patients whose tumors strongly and diffusely expressed ER and PR were more likely to experience improved PFS.
Researchers evaluated 2.5 mg daily doses of letrozole (Femara, Novartis) — an aromatase inhibitor — in 26 patients whose tumors expressed ER and/or PR. The median age of patients was 56 years (range, 44-74).
Patients had received a median of two prior treatment regimens (range, 0-9).
Researchers performed tumor assessments at baseline, 6 weeks and 12 weeks, and then every 8 weeks thereafter.
PFS at 12 weeks served as the primary outcome.
Median duration of letrozole treatment was 2.2 months (range, 0.4-9.9).
Twelve-week PFS was 50% (90% CI, 30-67). Fourteen patients (54%; 90% CI, 36-71) achieved stable disease.Three patients whose tumors expressed ER and PR in >90% of tumor cells continued with study treatment for more than 24 weeks.
The most common adverse events associated with letrozole were hot flashes (n=17) and muscle pain (n=8). Researchers observed grade 3 adverse events in three patients (12%).
Disease progression was the most common reason for treatment discontinuation (85%).
“We did observe a nonstatistically significant trend toward longer PFS in patients with tumors that more strongly expressed ER/PR, which may be related to the underlying more favorable biology of these tumors,” the researchers wrote. “However, in patients with very high expression of both ER and PR … there was significantly longer PFS, including among patients with active disease progression at the time of the study entry, suggesting that aromatase inhibition may play a role in disease control in this highly selected population of patients.”
Disclosure: The researchers report grants, personal fees, consultant fees and travel support from, as well as advisory roles with, Ariad Pharmaceuticals, Bayer, GlaxoSmithKline, Johnson & Johnson, Merck, Novartis, Pfizer and ZioPharm Oncology Inc.
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