Targeting estrogen receptor increases progression-free survival in advanced breast cancer

Fulvestrant significantly increases progression-free survival in women with positive advanced breast cancer, particularly those with less aggressive lower-volume disease, reports a recent research.

Fulvestrant is a selective estrogen receptor degrader that targets the function of the hormone receptor so, unlike aromatase inhibitors such as anastrozole, it does not interfere with estrogen levels themselves.

The randomized, double-blind, multi-center phase III trial enrolled 462 women with inoperable locally-advanced or metastatic ER-positive, HER-negative breast cancer, who had not received prior hormone therapy.

Half the patients (n=230) were randomized to 500mg intramuscular injections of fulvestrant (Days 0, 14, 28, then every 28 days), or to 1mg of anastrozole daily (n=232), and were also allowed one line of chemotherapy.

After a median follow-up of 25 months, patients treated with fulvestrant had a statistically significant 21 percent improvement in progression-free survival compared to those treated with anastrozole (16.6 months vs. 13.8 months, p = 0.048).

However, subgroup analysis showed an even greater impact on progression-free survival in patients whose disease had not spread to the liver or lungs at baseline (22.3 vs. 13.8 months).

Study's principle investigator Matthew Ellis said, "For patients with non-visceral disease whose life isn't immediately threatened by breast cancer - a group for whom physicians would typically choose endocrine therapy as a first approach - it looks like fulvestrant could be a new standard of care compared to anastrozole."

Both groups showed a similar health-related quality of life and the most common adverse events were arthralgia (joint pain) (16.7 percent vs. 10.3 percent) and hot flushes (11.4 percent vs. 10.3percent) for fulvestrant and anastrozole, respectively.

"It's tolerated as well as anastrozole, and better than other drugs that could potentially be used in this setting such as chemotherapy or CDK4 inhibitors," Ellis said.

Adding, "In patients for whom you are looking for a low toxicity approach, such as older patients or those with low volume disease, it looks like a good option."

Researchers also observed a significantly greater duration of response to treatment in the fulvestrant group compared to the anastrozole group, which Ellis suggested could account for the increase in progression-free survival.