A new treatment option for progressive hormone receptor-positive breast cancer

This study examined the effectiveness of palbociclib (Ibrance) in the treatment of hormone receptor-positive breast cancer patients. The authors found that palbociclib treatment increased progression free survival.

Major treatment options for hormone receptor-positive (HR+, dependent on the hormones estrogen and/or progesterone for growth) breast cancers are therapies that block the effects of estrogen. In some women, though, the cancer progresses despite hormone therapy. While anti-estrogen drugs, such as fulvestrant (Faslodex), have been found to be helpful for progressive cancer, additional treatments are often needed.

Palbociclib is a new treatment that blocks cancer cell growth. Palbociclib received accelerated approval by the U.S. Food and Drug Administration (FDA) in September 2015. Preliminary phase 2 studies have shown that the combination of palbociclib and the anti-estrogen letrozole (Femara) led to longer progression-free survival (time from treatment until disease progression). Large late-phase trials are currently underway to confirm the effectives and safety of palbociclib.

The study examined the effectiveness of palbociclib in combination with fulvestrant in breast cancer patients who progressed despite prior hormone therapy. 521 patients with HR+, HER2-negative (not dependent on HER2 for growth) breast cancer were included in this study. 347 patients received palbociclib and fulvestrant, while 173 received a placebo and fulvestrant. Both pre- and post-menopausal women were included in this study.

Average progression-free survival for patients treated with palbociclib was 9.2 months, compared to 3.8 months for those treated with placebo. Time to progression was similar for both pre- and post-menopausal women.

The most common adverse (negative) effects for those treated with palbociclib included low white blood cell levels (25.2%-62%), fatigue (2.0%) and anemia (low red blood cell levels, 2.6%).

This study concluded that a combination of palbociclib and fulvestrant led to longer progression-free survival in advanced progressive HR+ breast cancer patients.

This study was funded by Pfizer, the manufacturers of palbociclib.