Overall Survival with Inavolisib in PIK3CA-Mutated Advanced Breast Cancer.

Background: In the phase 3, double-blind, randomized INAVO120 trial, treatment with inavolisib plus palbociclib-fulvestrant led to a significant progression-free survival benefit, as compared with placebo plus palbociclib-fulvestrant, among patients with PIK3CA-mutated, hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative locally advanced or metastatic breast cancer who had had relapse during or within 12 months after completion of adjuvant endocrine therapy.

Methods: We randomly assigned patients with PIK3CA-mutated, hormone receptor-positive, HER2-negative locally advanced or metastatic breast cancer who had had disease recurrence or progression during or within 12 months after completion of adjuvant endocrine therapy to receive inavolisib plus palbociclib-fulvestrant (inavolisib group) or placebo plus palbociclib-fulvestrant (placebo group). In the current report, we provide the results of the final analysis of overall survival, including updated data on efficacy and safety.

Results: A total of 161 patients were assigned to the inavolisib group, and 164 to the placebo group. After a median follow-up of 34.2 months in the inavolisib group and 32.3 months in the placebo group, the median overall survival was 34.0 months (95% confidence interval [CI], 28.4 to 44.8) with inavolisib and 27.0 months (95% CI, 22.8 to 38.7) with placebo (hazard ratio for death, 0.67; 95% CI, 0.48 to 0.94; P = 0.02 [prespecified boundary for statistical significance, P<0.0469]). An objective response occurred in 62.7% (95% CI, 54.8 to 70.2) of patients in the inavolisib group and 28.0% (95% CI, 21.3 to 35.6) of those in the placebo group (P<0.001). The updated hazard ratio for disease progression or death was 0.42 (95% CI, 0.32 to 0.55). Adverse events led to discontinuation of inavolisib in 6.8% of patients and discontinuation of placebo in 0.6%. The incidence of hyperglycemia, stomatitis or mucosal inflammation, gastrointestinal toxic effects (e.g., diarrhea), and ocular toxic effects (e.g., dry eye and blurred vision) was higher with inavolisib than with placebo.

Conclusions: Treatment with inavolisib plus palbociclib-fulvestrant led to a significant overall survival benefit, as compared with placebo plus palbociclib-fulvestrant. Hyperglycemia, stomatitis or mucosal inflammation, gastrointestinal toxic effects, and ocular toxic effects were reported more frequently with inavolisib than with placebo. (Funded by F. Hoffmann-La Roche; INAVO120 ClinicalTrials.gov number, NCT04191499.).