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New breast cancer drug doubles progression free survival time

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Breast cancer researchers from the Revlon/UCLA Women’s Cancer Research Program at UCLA’s Jonsson Comprehensive Cancer Center (JCCC) have concluded clinical trials on a promising now drug to combat estrogen receptor positive (ER+) breast cancer. They announced their findings on April 7 at the American Association for Cancer Research (AACR) Annual Meeting 2014, which is being held from April 5 through April 9 in San Diego.

Earlier this year, the anti-cancer drug palbociclib (PD 0332991), manufactured by Pfizer, Inc. was given Breakthrough Therapy designation by the Food and Drug Administration (FDA). At the AACR meeting, the researchers noted that the drug essentially double the time that advanced breast cancer patients were on treatment without their cancer becoming worse, a situation known as progression-free survival.

Before conducting human trials, the investigators tested the drug in the laboratory against different types of cultured human breast cancer cells. The results were extremely encouraging for activity ER+ cancer cells. Thus, they conducted a clinical study in collaboration with Pfizer. The research team was headed by Dr. Richard S. Finn, associate professor of medicine at the UCLA cancer center. The new study was based upon research conducted by a research team led by Dr. Dennis Slamon, professor of medicine at JCCC and director of the Revlon/UCLA Women’s Cancer Research Program.

The first phase of the human trial, led by Dr. Finn and Slamon had a goal of determining the doses and initial safety results of a combination of palbociclib and letrozole, which is a commonly used drug for ER+ advanced breast cancer. Once the phase 1 study was completed, the phase 2 study was performed on 165 post-menopausal breast cancer patients with advanced ER+, HER2- disease. Dr. Finn explained, “By combining the test drug, palbociclib, with the standard drug letrozole, we demonstrated a dramatic and clinically meaningful effect on progression-free survival in women with ER+ advanced breast cancer. We are gratified and excited that these results confirm the preclinical work we began at the Translational Lab.”

The researchers found that progression-free survival was 20.2 months for patients who received palbociclib plus letrozole, compared to 10.2 months for those women who only received letrozoley. Thus, addition of palbociclib resulted in a 51% percent reduction in the risk of disease progression. Dr. Slamon explained, “Our final results very much validate the Translational Laboratory approach, By identifying the effective treatment targets in the correct patients, we advance personalized cancer treatment that we hope will greatly improve outcomes for this group of women with breast cancer. These results are as exciting as the initial results we saw for trastuzumab (Herceptin) in HER2+ breast cancers, but represent a new approach for women with ER+ advanced breast cancer. This group is different from HER2+ breast cancer and affects approximately 60% of all advanced breast cancer patients compared with approximately 20 percent for HER2.”