Palbociclib – Hope For Some With Metastatic Breast Cancer

A new drug – Palbociclib (IBRANCE®) for post-menopausal patients with Stage 4 estrogen-receptor positive, Her2 negative (ER+/Her2-) tumors has received an accelerated approval from the FDA, expanding treatment options for a group that represents approximately 60% of the advanced cancer population. The FDA's accelerated approval program speeds the development and approval of promising therapies that treat a serious or life-threatening condition and provide meaningful therapeutic benefit over available therapies.

In a Pfizer-sponsored Phase 2 PALOMA-1 trial, when Palbociclib was taken with letrozole (Femara®), progression-free survival in women with metastatic breast cancer was nearly doubled to 20.2 months, compared with 10.2 months when only letrozole was taken. While delaying the tumor's growth may be beneficial, since it could lead to a better quality of life, the drug has yet to show benefits in extending overall survival, which could be the more desired option.

FDA's Dr. Richard Pazdur expressed that the combination "provides a novel treatment option to women diagnosed with metastatic breast cancer." The Pfizer drug (Palbociclib), the first in its class to be approved by FDA, works by inhibiting cyclin-dependent kinases (CDKs) -4 and -6, thereby preventing the over proliferation of cancer cells.

Palbociclib is taken once daily orally (125 mg), for the first 21 days with letrozole (2.5 mg), followed by a 7-day off treatment that rounds off a 28-day cycle. Pfizer provides a list of serious and most common side effects when Palbociclib is taken with letrozole.

However, as with all cancer treatments, cost is always a concern. Pfizer has said that it would likely price Palbociclib at $9,850 a month, or $118,200 per year - a sum that, without comprehensive health plans, government concessions or other financial aid, would hardly be affordable to many. As with any medication, side effects are also a concern. It is reported that toxicity is "tolerable" for patients. However, the issue of diminished white blood cells and the consequent risk of infection on more than half of the patients along with other side effects such as severe diarrhea, severe back pain and pulmonary embolism leaves these concerns unaddressed.

The approval of Palbociclib offers another option to some but not necessarily to others because of cost and side effects that are too severe. Finally, the drug is not indicated for every type of metastatic breast cancer or treatment history.


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