I imagine others are discussing this in various portions of the forum, but in a nutshell, the FDA granted accelerated approval to Pfizer's palbociclib (Ibrance) [a CDK inhibitor], a pill for use in patients with MBC. When given in combination with letrozole (Femara), the new drug extends progression-free survival in post-menopausal patients with Stage 4 estrogen-receptor (ER) positive, Her2 negative (ER+/Her2-) tumors.
In a randomized trial, Palbociclib nearly doubled progression-free survival in women with metastatic breast cancer, from 10.2 to 20.2 months.

The drug was approved based on results of an open (non-blinded) Pfizer-sponsored phase 2 trial called PALOMA-1. The results look at two patient cohorts with median follow-up of 27-30 months. The 165 patients, all postmenopausal women with stage 4, ER+/Her2- breast cancer, enrolled between Dec 2009 and May 2012. The women were randomized to receive either letrozole (an AI) alone or in combination with palbociclib, taken once daily for 21 days out of every 28.

Roughly 13% dropped out of the study, likely due to toxicity issues (the article didn't specifically cite why they dropped out).

I'll be starting this soon. I picked it up yesterday and it cost a little over $12,000.00. I have coverage so didn't pay anything. I have to get a specific shot before starting. That's for my case, not really part of program.