SOLAR-1: OS data support PFS findings for fulvestrant plus alpelisib
medwireNews: Adding alpelisib to fulvestrant improves overall survival (OS) in people with PIK3CA-mutated, hormone receptor-positive, HER2-negative advanced breast cancer, but not significantly so, show data from the phase 3 SOLAR-1 trial.
“Although the analysis did not cross the prespecified boundary for statistical significance, there was a 7.9-month numeric improvement in median OS when alpelisib was added to fulvestrant treatment,” Fabrice André (Institut Gustave Roussy, Villejuif, France) and colleagues write in the Annals of Oncology.
The primary findings of the SOLAR-1 trial, reported by medwireNews, showed that progression-free survival (PFS) time was doubled among individuals with PIK3CA-mutated, hormone receptor-positive, HER2-negative advanced breast cancer who received the PI3K inhibitor alpelisib plus fulvestrant relative to those who received placebo plus fulvestrant.
The current analysis was conducted after a median 42.4 months of follow-up. At this time 51.5% of the 169 men and postmenopausal women who were randomly assigned to receive alpelisib (300 mg/day) plus fulvestrant (500 mg every 28 days and once on day 15) had died compared with 54.7% of the 172 individuals assigned to receive placebo plus fulvestrant.
Median OS was 39.3 and 31.4 months in the alpelisib and placebo groups, respectively, giving a nonsignificant hazard ratio for death of 0.86 in favor of alpelisib.
The researchers also found that “OS was numerically improved in hard-to-treat disease,” including patients with lung and/or liver metastases, at a median of 37.2 months in the alpelisib plus fulvestrant arm versus 22.8 months in the placebo plus fulvestrant arm.
In addition, a post-hoc exploratory analysis revealed that 56.2% of participants in the alpelisib arm and 63.4% of those in the placebo arm went on to receive their first chemotherapy in the metastatic setting, with median times to chemotherapy of 23.3 and 14.8 months, respectively.
Furthermore, the researchers say that at the time of their analysis “3 times as many patients still remained on therapy in the alpelisib plus fulvestrant arm than in the placebo plus fulvestrant arm (21 vs 7 patients),” which they describe as “notable considering the poor prognosis of these patients with PIK3CA-mutated disease.”
André and team observed no new safety signals and state that the rate of hyperglycemia did not increase with additional follow-up, while rash adverse events of special interest were generally low grade and consistent with previous reports.
They conclude: “Overall, these results further support the statistically significant prolongation of PFS observed with alpelisib plus fulvestrant in this population, which has a poor prognosis due to a PIK3CA mutation.”
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