SAN ANTONIO — Dasatinib inhibited aromatase inhibitor resistance in postmenopausal women with locally recurrent or metastatic breast cancer, according to results of a small phase 2 study presented at the San Antonio Breast Cancer Symposium.
“Maybe the benefit from dasatinib would be in patients initially being placed on aromatase inhibitors,” Dev Paul, DO, PhD, breast oncologist at US Oncology and Rocky Mountain Cancer Centers in Denver, Colo., said during a press conference.
The non-comparative, parallel group study included 120 postmenopausal patients with ER-positive, HER-2–negative disease.
Researchers randomly assigned 57 patients to letrozole 2.5 mg/day in conjunction with dasatinib (Sprycel, Bristol-Myers Squibb) 100 mg/day. The other 63 patients received letrozole alone.
Clinical benefit rate served as the primary outcome measure.
Researchers reported a 71% clinical benefit rate for letrozole plus dasatinib,compared with 66% for letrozole alone. Thirty-five patients initially assigned to letrozole alone crossed over into the dasatinib arm, and the clinical benefit rate among those patients was 23%.
PFS served as the secondary outcome measure.
Paul and colleagues reported PFS of 20.1 months among patients assigned to dasatinib vs. 9.9 months for patients assigned to letrozole alone. The HR of 0.69 is exploratory due to the nature of the study.
A greater percentage of patients assigned to letrozole alone had a T-score less than -1.5 (32% vs. 14%). Biphosphonate treatment was similar in the two groups.
“This is a preliminary exploratory study and the clinical benefit rate was the same, but this progression-free [survival] doubling is interesting to us,” Paul said. “It’s a small study. It’s interesting and will lead to more studies.”
For more information:
Paul D. Abstract #S3-07. Presented at: San Antonio Breast Cancer Symposium; Dec. 10-14, 2013; San Antonio.
The study was supported by funds form Bristol-Meyers Squibb. Paul reports no relevant financial disclosures.