A new breast cancer drug, fulvestrant, has been approved for the treatment of hormone-receptor positive breast cancer in postmenopausal women whose cancer is progressing despite antiestrogen therapy, usually tamoxifen. This drug is the first addition to the breast cancer armamentarium since 1999.

Efficacy. Fulvestrant 250 mg once monthly was compared with the aromatase inhibitor anastrazole 1 mg/day in two phase III clinical trials, one in North America and one in Europe. All patients had breast cancer progression despite previous therapy with an antiestrogen or progestin. After therapy began, patients were followed up monthly for the first 3 months and every 3 months thereafter. The North American trial was a double-blind, randomized trial that included 400 postmenopausal women; the European trial was an open, randomized trial including 451 women. The primary effectiveness end points were response rates, based on the Union Internationale Contre le Cancer criteria, and time to progression.

The drugs performed similarly in both trials. After a minimum follow-up of 14.6 months, the tumor response rate in the North American trial was the same with both drugs (17% of patients); in the European trial, the rates were similar (20% of fulvestrant patients versus 15% of anastrazole patients). Time to progression was 5.5 months for fulvestrant versus 3.5 months for anastrazole in the North American trial and 5.5 months versus 5.2 months in the European trial.

Safety. Women should be advised not to become pregnant while receiving this drug because it may harm the fetus. In addition, there is potential for serious adverse reactions in nursing infants. The most commonly reported adverse events with both drugs were gastrointestinal symptoms (including nausea, vomiting, constipation, diarrhea, and abdominal pain), headache, back pain, hot flushes, and pharyngitis. Mild and transient injection-site reactions occurred in 7% of patients who received one injection (ie, one 5 ml injection; the European trial) and 27% of patients who received two injections (ie, two 2.5 ml injections; the North American trial).

Dosing. For adults, including the elderly, the recommended dose is 250 mg IM per month and can be administered as a single 5-ml injection or two 2.5-ml injections slowly into the buttock.

Pricing. The wholesale acquisition cost for a once monthly injection is $737.50.