THURSDAY, Oct. 31, 2024 (HealthDay News) — Inavolisib plus palbociclib-fulvestrant yields significantly longer progression-free survival than placebo plus palbociclib-fulvestrant in patients with PIK3CA-mutated, hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative locally advanced or metastatic breast cancer, according to a study published in the Oct. 31 issue of the New England Journal of Medicine.

Nicholas C. Turner, M.D., Ph.D., from the Royal Marsden Hospital in London, and colleagues conducted a double-blind, randomized trial comparing first-line inavolisib plus palbociclib-fulvestrant (inavolisib group; 161 patients) to placebo plus palbociclib-fulvestrant (placebo group; 164 patients) in patients with PIK3CA-mutated, hormone receptor-positive, HER2-negative locally advanced or metastatic breast cancer who had had a relapse during or within 12 months of adjuvant endocrine therapy completion.

The researchers found that the median progression-free survival was 15.0 and 7.3 months in the inavolisib and placebo groups, respectively (hazard ratio for disease progression or death, 0.43). An objective response occurred in 58.4 and 25.0 percent of patients in the inavolisib and placebo groups, respectively. In the inavolisib and placebo groups, the incidence of grade 3 or 4 neutropenia was 80.2 and 78.4 percent, respectively. The corresponding incidence rates were 5.6 and 0 percent for grade 3 or 4 hyperglycemia; 5.6 and 0 percent for grade 3 or 4 stomatitis or mucosal inflammation; and 3.7 and 0 percent for grade 3 or 4 diarrhea. There was no grade 3 or 4 rash reported. Overall, 6.8 and 0.6 percent of patients in the inavolisib and placebo groups had discontinuation of any trial agent because of adverse events.

“Inavolisib plus palbociclib-fulvestrant may represent a new treatment option for these patients,” the authors write.

The study was funded by F. Hoffmann-La Roche, a subsidiary of which manufactures inavolisib (Genentech).

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