SABCS 2014: PI3K Inhibition With Pictilisib in Hormone Receptor–Positive Breast Cancer Not Ready for Prime Time

The gist: Researchers are hoping a treatment approach called ‘PI3K inhibition’ might improve outcomes for people with hormone receptor-positive breast cancer. But it’s unclear whether the approach will be successful, and a recent attempt did not give stellar results. In a clinical trial, researchers gave patients the PI3K inhibitor drug pictilisib along with the drug fulvestrant (Faslodex). It did not significantly lengthen the amount of time patients went without their cancer worsening. But later analysis showed that it did stave off cancer getting worse in certain patients: women whose breast cancer is both estrogen receptor-positive (ER+) and progesterone receptor–positive (PR+). Further research is needed to see if any PI3K drugs are particularly effective. For more information, click through to the full article and see this other article from Cancer Network.

“Interest is high in studying the PI3K pathway in hormone receptor–positive breast cancer, but it is not clear which of the PI3K inhibitors under development—if any—will be a ‘home run.’

“Adding the pan-class I selective PI3K inhibitor pictilisib to fulvestrant (Faslodex) did not significantly improve progression-free survival in women with estrogen receptor–positive breast cancer, but in an exploratory analysis of the trial, progression-free survival was significantly extended in women with both estrogen receptor–positive and progesterone receptor–positive breast cancer. The findings were presented at the 2014 San Antonio Breast Cancer Symposium (Abstract S2-02).

“ ‘When we considered only women with breast cancer positive for both estrogen receptor and progesterone receptor, adding pictilisib resulted in a significant doubling of progression-free survival in an exploratory analysis. We plan to investigate whether the benefit of pictilisib for women with estrogen receptor-/progesterone receptor–positive breast cancer holds true in an additional cohort of patients within this study,’ stated lead author Ian Krop, MD, Director of Clinical Research for the Breast Oncology Program at the Dana-Farber Cancer Institute, Boston.”