New Treatment For ER Positive Breast Cancer: Checking Up On Cell Cycle Inhibitors.

One of the common mechanisms involved in advanced stage metastatic ER positive breast cancer is amplification of cell dependent kinases (CDKs) 4/6. Over activation of these two genes enables tumor cell progression from G1 to S phase of the cell cycle, which is necessary for DNA replication and cell division.

Palbociclib is an oral and selective inhibitor of CDK 4/6 that has recently been shown to greatly increase the progression free survival of woman with hormone resistant metastatic breast cancer. A recent phase II study combining palbociclib with letrozole resulted in a 26.1 month progression free survival rate compared with only 7.5 months for letrozole alone.

I like this approach because it provides a highly effective treatment that specifically targets the cell cycle of cancer cells unlike standard chemotherapy, which inhibits the cell cycle of all body cells, resulting in harsh and damaging side effects.

A Phase III Study Of Palbociclib For The Treatment Of Postmenopausal Women With ER Positive Breast Cancer.

UPDATE: Based on these data, Pfizer has initiated an International Phase 3 study evaluating palbociclib in combination with letrozole versus letrozole alone as a first line treatment for post-menopausal patients with ER positive metastatic breast cancer.


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