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First-line fulvestrant extended OS in advanced, ER-positive breast cancer
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SAN ANTONIO — First-line fulvestrant significantly extended OS compared with anastrozole in women with advanced, ER-positive breast cancer, according to results of the phase 2 FIRST study presented at the San Antonio Breast Cancer Symposium.
Prior research demonstrated fulvestrant (Faslodex, AstraZeneca) was associated with prolonged disease control compared with anastrozole (Arimidex, AstraZeneca) in the second-line setting.
“It is quite unusual to see a difference in time to progression and survival in the second-line setting,” said John Robertson, MD, professor of surgery at the Graduate Entry Medical School at the University of Nottingham and Royal Derby Hospital in the United Kingdom. “When we saw this we were excited because it wasn’t something that we had seen before in this context.”
John Robertson
The current, multicenter analysis included 205 women with advanced, ER-positive breast cancer. Robertson and colleagues randomly assigned patients 1:1 to first-line treatment with 500 mg fulvestrant or 1 mg anastrozole.
Previously reported results from the analysis indicated a similar proportion of patients in the fulvestrant and anastrozole arms achieved a clinical benefit (72.5% vs. 67%; OR=1.3; 95% CI, 0.72-2.38). The median time to progression was considerably longer in the fulvestrant arm (23.4 months vs. 13.1 months; HR=0.66; 95% CI, 0.47-0.92).
The current analysis includes data from 170 patients, 137 of whom had died. Median follow-up was 49.6 months in the fulvestrant arm and 42.5 months in the anastrozole arm.
Median OS was 54.1 months among women assigned fulvestrant compared with 48.4 months among women assigned anastrozole. Fulvestrant was associated with a 30% reduction in the risk for death compared with anastrozole (HR=0.7; 95% CI, 0.5-0.98).
The OS benefit associated with fulvestrant was consistent across subgroups for age, hormone receptor status and prior treatments, Robertson said.
Adverse events occurred in 23.8% of patients in the fulvestrant arm and 21.4% of patients in the anastrozole arm, and no new safety events occurred.
“Despite the improved disease control on treatment and improved OS seen in the FIRST study, we do not expect this to change the standard of care at this point since it was a phase 2 study,” Robertson said in a press release. “A phase 3 study [FALCON] has been initiated to support the regulatory approval for fulvestrant as a first-line agent in this setting, which would be practice changing.”
Disclosure: The researchers report research funding, travel expenses and honoraria from and advisory roles with Amgen, AstraZeneca, Bayer, Novartis and Pfizer.
Perspective
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Aditya Bardia, MD, MPH
To see an OS benefit with fulvestrant as opposed to anastrozole is very encouraging. However, three issues need to be considered. First, these are phase 2 results, so we need phase 3 results before we can use them to change practice. Second, it would also be important to go back and look at patients who had received aromatase inhibitors in the adjuvant setting. A number of patients would have received aromatase inhibitors because they are FDA approved in that setting, but fulvestrant is not. Whether there is a difference in that population as opposed to newly diagnosed metastatic breast cancer would be important to discern. Finally, there is an emerging interest in understanding the molecular underpinnings of breast cancer, and it is important to identify whether driver mutations (eg, PI3 kinase mutations) were equally balanced in both arms, and whether that has an impact on outcomes. This would guide future research and treatment strategies for metastatic breast cancer.Click Here to Manage Email Alerts