SOLAR-1: Predicting Response to Alpelisib in PIK3CA-Mutant Breast Cancer
Posted: Monday, January 14, 2019
At the 2018 San Antonio Breast Cancer Symposium (SABCS), Dejan Juric, MD, of Massachusetts General Hospital Cancer Center, Boston, and his colleagues presented data from the phase III SOLAR-1 trial indicating that adding alpelisib, α-specific PI3K inhibitor, to fulvestrant provided a clinical benefit in patients with PIK3CA-mutant advanced breast cancer (Abstract GS3-08). Assessing mutational status by liquid biopsy resulted in an even larger clinical benefit than tissue biopsy, improving the median progression-free survival from 3.7 to 10.9 months.
“Our analysis reveals that [patients with] advanced breast cancer with detectable PIK3CA mutations in their blood have a more impressive benefit when alpelisib is added to fulvestrant for their treatment compared to patients with PIK3CA mutations detected in their tissue,” said Dr. Juric in an SABCS press release.
A total of 341 patients with hormone receptor–positive, HER-2 negative advanced breast cancer were randomly assigned in the PIK3CA cohort to receive either alpelisib and fulvestrant (169) or fulvestrant with a placebo (172). After a median of 20 months, 40 deaths occurred in the alpelisib group compared with 52 deaths in the placebo group. In addition, patients who had the PIK3CA mutation present in their tissue had a 35% risk reduction in progression-free survival as compared with a 45% risk reduction for those who had the mutation in circulating tumor DNA. Patients who received alpelisib as second-line treatment for metastatic disease had a 39% risk reduction in disease progression. The overall survival results were immature at data cutoff.
Adverse events associated with the combination therapy included hyperglycemia (65%), diarrhea (54%), nausea (46%), and rash (40%). Approximately 3% of patients stopped the treatment due to adverse events associated with alpelisib and fulvestrant.
Disclosure: Study authors’ disclosure information may be found at sabcs.org.
