Conclusions
The BELLE-2 study met its primary endpoint, demonstrating a modest PFS improvement for
combined buparlisib and fulvestrant in postmenopausal women with HR+/HER2– advanced
breast cancer that had progressed after prior AI therapy
Frequent discontinuations due to adverse events reduced treatment duration in the buparlisib
arm, potentially limiting the efficacy of combination therapy
Patients with tumors harboring PIK3CA mutations detected in ctDNA performed poorly on
fulvestrant monotherapy, achieving PFS improvement with the combination
–
3.8 month PFS improvement was supported by higher
response rates (18.4% vs 3.5%) in this patient
population
The BELLE-2 study suggests that assessment of PIK3CA mutations in ctDNA may help select
patients who would benefit from adding a PI3K inhibitor to endocrine therapy
Phase III studies with PI3Kα-selective inhibitors are underway to confirm the predictive value
of PIK3CA mutations detected in ctDNA and tumor tissue
1
6
0
9
0
4
3
6
8
1
