Endocrine therapy has been a trusted therapy for breast cancer. In this trial, we tried to explore the possibilities of Palbociclib. Palbociclib added to endocrine therapy improves progression-free survival. Not just this, but it also helps with the patients of hormone-receptor-positive, HER2-negative, metastatic breast cancer. The test conducted was for observing the effect of additional Palbociclib on this therapy.

Worldwide the trial went on to 406 cancer centers in 21 countries.  From Sept 1, 2015, to Nov 30, 2018, 5760 patients randomly went through the process of this technique. Further  23· 7months (IQR 16·9–29·2), 170 of 2883 patients were given palbociclib plus endocrine therapy. On the other side, 181 of 2877 assigned to endocrine therapy alone had invasive disease-free survival events. Neutropenia was the most common grade 3–4 adverse event. 61·3% of the combined dose patients had this effect, while less than 0.3% of the total without the dose reported this. Other effects were leukopenia in 30.2% of the combined dose and fatigue in 2.1%. No treatment-related death happened. 

Even after the second interim analysis, an extension of 2 years of adjuvant palbociclib to adjuvant endocrine therapy was given. But the results were on the negative side, and no improvement in survival was seen.

https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(20)30642-2/fulltext