Faslodex (chemical name: fulvestrant) is a type of hormonal therapy medicine used to treat post-menopausal women diagnosed with advanced-stage hormone-receptor-positive breast cancer in two situations:
Hormonal therapy medicines working by blocking the effects of estrogen on breast cancer cells or by lowering the amount of estrogen the body produces.
Two studies on Faslodex are reviewed here. One study found that advanced-stage, hormone-receptor-positive breast cancers treated with 500 mg of Faslodex (double the usual dose) had a slightly better response than cancers treated with 250 mg of Faslodex (the usual dose). The other study found that using Faslodex and Arimidex (chemical name: anastrozole) together was no better than Arimidex alone for treating advanced-stage breast cancer. These results were presented at the 2009 San Antonio Breast Cancer Symposium.
Faslodex is an estrogen receptor downregulator (ERD). Like tamoxifen, Faslodex works by blocking estrogen receptors. Faslodex sits in the estrogen receptors in breast cells. If Faslodex is in the estrogen receptor, there is no room for estrogen and it can't attach to the cell. If estrogen isn't attached to a breast cell, the cell doesn't receive estrogen's signals to grow and multiply. Faslodex also:
In the study that compared the usual dose of Faslodex with double the usual dose, 736 women diagnosed with advanced-stage, hormone-receptor-positive breast cancer had previously been treated with either tamoxifen (called an antiestrogen in the study) or an aromatase inhibitor. Still, the breast cancer came back (recurred) or grew.
Half the women got 250 mg of Faslodex (the standard dose) and the other half got 500 mg of Faslodex. Faslodex is injected into a muscle once a month.
Doctors checked the cancers every 12 weeks to see if the Faslodex was having any effect. The likelihood of the cancer responding to Faslodex was the same for both doses. Still, there were differences in the way the cancers responded to the different doses. Among women who got 500 mg of Faslodex:
Side effects and overall quality of life were the same for both groups of women.
These results suggest that Faslodex can be a good hormonal therapy option to treat breast cancer that comes back as advanced-stage disease or advanced-stage breast cancer that progresses after being treated with either tamoxifen or an aromatase inhibitor. The researchers said 500 mg now should be the standard dose.
In the study that compared Faslodex and Arimidex to Arimidex alone, 514 women diagnosed with advanced-stage, hormone-receptor-positive breast cancer had been treated with chemotherapy, hormonal therapy, or both before the cancer grew. Half the women got the aromatase inhibitor Arimidex and the standard dose of Faslodex. The other half got only Arimidex.
Aromatase inhibitors work by reducing the amount of estrogen produced in the body. The aromatase inhibitors are: Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), and Femara (chemical name: letrozole).
There was no difference in response to the two treatments. This suggests that Faslodex is best used by itself after another hormonal therapy medicine doesn't work or stops working.
If you've been diagnosed with advanced-stage, hormone-receptor-positive breast cancer, either as a recurrence or as the initial diagnosis, you and your doctor will consider a number of treatment options, including hormonal therapy and chemotherapy. Because the breast cancer is hormone-receptor-positive, hormonal therapy medicines are still good treatment options even if you've been treated with hormonal therapy in the past. Faslodex, which works differently than tamoxifen and the aromatase inhibitors, might be a good choice, depending on your unique situation. If your doctor does recommend Faslodex, you might want to ask how much you'll receive. If the standard dose (250 mg) is recommended, consider asking your doctor about the first study reviewed here and whether the higher dose (500 mg) makes sense for you. Together, you and your doctor will decide on a treatment plan that is best for you.
SAN ANTONIO (MedPage Today) -- Women with metastatic breast cancer had a modest but statistically significant improvement in time to progression when treated with 500 mg of fulvestrant (Faslodex) -- double the usual dose -- data from a multinational phase III trial showed.
The one-month delay in progression came with no increase in adverse effects, Angelo Di Leo, MD, of the Hospital of Prato in Prato, Italy, said at the San Antonio Breast Cancer Symposium.
The higher dose was also associated with a trend toward a reduced mortality risk. Other outcomes were similar between the two dose groups.
The benefits were consistent across all prespecified subgroups.
"Fulvestrant will continue to be used after tamoxifen and aromatase inhibitors, but I believe the 500-mg dose will become the standard," said Di Leo.
A second study reported at the San Antonio meeting showed that adding the estrogen-receptor antagonist to an aromatase inhibitor did not improve time to progression compared with the aromatase inhibitor alone.
Available for more than a decade, fulvestrant has been overshadowed by other endocrine therapies for breast cancer, C. Kent Osborne, MD, of Baylor College of Medicine in Houston, said at a press briefing.
The lack of recognition can be traced, in part, to suboptimal use of the estrogen-receptor inhibitor, including an inadequate dose, he said.
Di Leo reported findings from a randomized clinical trial designed to examine the fulvestrant dosing issue. The study involved 736 patients with estrogen receptor-positive advanced breast cancer. All patients had disease progression or recurrence after prior treatment with an antiestrogen agent or an aromatase inhibitor.
Patients were randomized to 250 or 500 mg of fulvestrant monthly and assessed for tumor response every 12 weeks. The primary endpoint was time to progression, and secondary endpoints included overall response, clinical benefit (response plus stable disease ≥24 weeks), duration of clinical benefit, overall survival, and safety and tolerability.
The 500-mg dose led to a median time to progression of 6.5 months compared with 5.5 months for patients treated with the standard 250-mg dose (P=0.006).
Overall survival improved by 16% with the higher dose, but the difference was not significant from the improvement seen with the 250-mg group (HR 0.84, P=0.091).
Overall response rate was 14% to 15% in each group. Total clinical benefit was 45.6% with 500 mg of fulvestrant and 39.6% with 250 mg. The median duration of clinical benefit was 16.6 months with the higher dose and 13.9 months with the standard dose, neither of which differed significantly.
Adverse-event rates and quality-of-life scores also were similar for the two groups.
Results of another multinational study demonstrated no advantage for adding fulvestrant to anastrozole (Arimidex). Time to progression and overall survival were virtually identical in patients treated with anastrozole alone or with the combination.
"The fulvestrant and anastrozole combination offers no clinical efficacy advantage over anastrozole alone and should not be used," concluded Joseph Bergh, MD, of the Karolinska Institute in Stockholm, Sweden.
Bergh reported data from a trial involving 514 patients in first relapse after adjuvant cytotoxic or hormonal therapy for locally advanced or metastatic breast cancer.
All patients received anastrozole 1 mg/d and were randomized to a 500-mg loading dose of fulvestrant followed by 250 mg/month or no additional therapy. About two thirds of the patients had received adjuvant endocrine therapy.
Analysis of the primary endpoint showed no difference in time to progression, 10.8 months with the combination and 10.2 months with anastrozole alone.
The two groups also did not differ with respect to key secondary endpoints, including overall survival (37.8% with the combination and 38.2% with anastrozole alone), response rate (31.8% versus 33.6%), and clinical benefit rate (55.0% versus 55.1%).
Both studies were supported by AstraZeneca.
Di Leo disclosed relationships with Bristol-Myers Squibb and sanofi-aventis.
Bergh disclosed relationships with Merck, Pfizer, AstraZeneca, sanofi-aventis, and Roche.
Primary source: San Antonio Breast Cancer Symposium Source reference: Di Leo A et al. "CONFIRM: A phase III, randomized, parallel-group, trial comparing fulvestrant 250 mng vs fulvestrant 500 mng in postmenopausal women with estrogen receptor-positive advanced breast cancer" SABCS 2009; Abstract 25.Additional source: San Antonio Breast Cancer SymposiumSource reference: Bergh J et al. "First results from FACT -- An open-label randomized phase III study investigating loading dose of fulvestrant combined with anastrozole at first relapse in hormone receptor-positive breast cancer" SABCS 2009; Abstract 22.
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