Dr. Richard S. Finn, associate professor of medicine at the Jonsson Comprehensive Cancer Center at the University of California, Los Angeles, said in the first part of this two-part, phase II study, the researchers randomly assigned 66 postmenopausal women with metastatic estrogen receptor-positive breast cancer to either the combination of PD 0332991 and letrozole or to letrozole alone.
Finn and colleagues said the second part of the study involved 99 patients with ER-positive cancers determined by screening to have certain genomic alterations -- specifically cyclin D1 amplification and/or p16 loss.
The findings found survival was 26.1 months for those in the combination treatment versus 7.5 months for patients treated with letrozole alone. There was also a 45 percent response rate with the combination treatment versus 31 percent with letrozole alone in patients with measurable disease, the study said.
The clinical benefit rate was 70 percent with the combination treatment and 44 percent with letrozole alone, Finn said.
The combination of PD 0332991 and letrozole was also well tolerated, the researchers said.
The findings were presented at The Cancer Therapy & Research Center -- American Association for Cancer Research San Antonio Breast Cancer Symposium.