A combination therapy using an experimental new drug shows significant promise for women with a common type of breast cancer in which estrogen causes their tumors to grow, researchers with the Revlon/UCLA Women’s Cancer Research Program at UCLA’s Jonsson Comprehensive Cancer Center report.

The treatment, which incorporates the standard anti-estrogen therapy letrozole and the experimental drug PD 0332991, developed by pharmaceutical company Pfizer Inc., was found to increase progression-free survival time — the length of time a patient is on treatment without tumor growth — in women with estrogen receptor–positive, HER2-negative cancer, compared with letrozole alone.

The results of a two-part, phase 2 clinical trial testing the new combination therapy were announced Dec. 5 at the 2012 CTRC–AACR San Antonio Breast Cancer Symposium in San Antonio, Texas, by Dr. Richard S. Finn, an associate professor of medicine at UCLA and a member of the Jonsson Cancer Center, who led the trial.