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The survival benefit obtained with Ibrance plus Faslodex persisted over a median follow-up of 73.3 months in patients with HR-positive, HER2-negative advanced breast cancer.
A combination of Ibrance (palbociclib) and Faslodex (fulvestrant) improved overall survival (the time from diagnosis or treatment when a patient is still alive) compared with placebo plus Faslodex in patients with HR-positive, HER2-negative advanced breast cancer.
Dr. Massimo Cristofanilli, associate director for translational research at the Lurie Cancer Center and a professor of medicine in the Division of Hematology/Oncology at Northwestern University Feinberg School of Medicine, presented the findings during the 2021 ASCO Annual Meeting.
“An improvement in (overall survival) with Ibrance plus (Faslodex) continues to be observed with more than six years of median follow up in patients with HR-positive advanced breast cancer who progressed on prior endocrine therapy,” Cristofanilli said. “This prolonged (overall survival) benefit is particularly evident in patients with endocrine-sensitive disease and those with prior exposure to chemotherapy in the advanced setting.”
Investigators in the phase 3 trial randomly assigned 521 patients with metastatic breast cancer whose disease progressed on or following endocrine treatment to Faslodex plus Ibrance (347 patients; median age, 57 years) or Faslodex plus placebo (174 patients; median age, 56 years).
The updated median overall survival for patients who received Ibrance plus Faslodex was 34.8 months versus 28 months in the placebo group. After a median follow-up of 44.8 months, the median overall survival was 34.9 months for those who received Ibrance plus Faslodex compared with 28 months for the placebo group.
“Remarkable in this metastatic setting is that the five-year (overall survival) rate is 23.3% in the (Ibrance group) compared with 16.8% in the placebo (group),” he added.
Cristofanilli noted that 34% of patients had received prior chemotherapy for advanced breast cancer and 35% received more than two lines of prior treatment. He said that these types of patients had been excluded from other phase 3 studies testing CDK4/6 inhibitors like Ibrance with Faslodex.
In patients who had not received prior chemotherapy for advanced disease, those who received Ibrance plus Faslodex had a median overall survival of 39.3 months, while the placebo group reported 29.7 months. In contrast, there was no survival benefit for the combination in patients who did receive chemotherapy previously.
Ibrance conferred an overall survival benefit regardless of ESR1 or PIK3CA mutation status, Cristofanilli said. Mutation status may predict overall survival benefit and was highly associated with shorter overall survival in patients with ESR1 mutation. PIK3CA mutations were also associated with shorter overall survival but the connection was weak.
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