Using palbociclib alone or with other therapies in advanced ER+ breast cancer

This study aimed to find out if the breast cancer treatment palbociclib (Ibrance) works better alone, or in combination with other endocrine therapies (drugs which act on hormone receptors) used to treat estrogen receptor positive (ER+ – a hormone receptor found on the tumor) breast cancer. The authors found that treating women with palbociclib plus their previously used endocrine therapy resulted in longer survival that just treatment with palbociclib alone.

ER+ breast cancer has receptors that are responsive to certain drugs (endocrine therapies). Palbociclib is a type of chemotherapy medication used to treat breast cancer. It has been shown to work well with therapies used for ER+ breast cancer. However, it is not known if it works well alone. Resistance of ER+ breast cancer to endocrine medications is common. There is potential that palbociclib can overcome this resistance.

This study took place over 4 years and recruited 115 women. These women had ER+ advanced breast cancer. They all previously had some form of endocrine treatment for their breast cancer. These women were either treated with palbociclib alone, or palbociclib in combination with the same endocrine treatment they had most recently used.

The authors found no difference in the clinical benefit (no progression of disease after 6 months) between the two treatments. The authors also found that those in the combination therapy group went longer without their disease getting any worse (10.8 months) compared to the palbociclib only group (6.5 months). All 57 patients who received a combination treatment experienced a side effect and 56 (97%) patients who received palbociclib alone experienced a side effect. These included a low white blood cell count and infection.

The study concluded that using palbociclib in combination with a previously used endocrine therapy results in longer survival than using palbociclib alone.

Only 115 patients were included in this trial. Some results were not statistically meaningful. More research needs to be done in this area.