June 7, 2010 (Chicago) -- A drug derived from sea sponges extended the lives of breast cancer patients whose cancer had come back -- despite as many as five rounds of chemotherapy -- by an average of two and a half months.
In the study of over 750 women, those who took the experimental drug eribulin lived an average of about 13 months, compared with about 10 1/2 months for women who did not take the drug.
While a few months might not sound like much, it can be a huge gain for seriously ill patients facing an imminent risk of dying, say doctors studying the drug.
"I've had women whose outlook is poor, facing [an average] survival time of about 10 months, tell me, 'I just want to make it to next year to see my child's fourth birthday, or my son's wedding,'" says study head Christopher Twelves, MD, PhD, of St. James Hospital in Leeds, England.
"Now there is a drug that we can add to their limited options," he tells WebMD.
Twelves presented results of the late-stage phase III trial at the annual meeting of the American Society of Clinical Oncology. He consults for Eisai, which makes eribulin and funded the study.
Breast Cancer Prognosis
Many of the more than 200,000 women diagnosed with breast cancer in the U.S. each year now have an excellent chance of becoming long-term survivors due to better treatments developed over the past few decades.
"But about 30% will develop advanced or metastatic disease that cannot be cured with current treatments," Twelves says.
Enter eribulin, a chemotherapy drug that targets the scaffolding protecting cells, stalling cell division and causing cells to die off. Some older chemo drugs such as taxanes also act on the scaffold, but on a different part.
The new study involved 762 breast cancer patients whose tumors had spread (metastasized) despite two to five rounds of different chemotherapy drugs.
Two-thirds of the women got eribulin, which is given as a short IV infusion two days, every three weeks. The rest received whatever treatment their doctor thought was best, usually another chemotherapy drug but sometimes only supportive care to treat pain and fatigue.
Women on eribulin were 19% less likely to die, the study shows. Their cancer also stayed in check slightly longer: 3.7 months vs. 2.2 months for women on standard treatment. Tumors shrank by 30% or more in 12.2% of women on eribulin vs. 4.7% of women in the other group.
Surprisingly, among women whose tumors did shrink, the duration of response was longer for women in the standard therapy group: 6.7 months vs. 4.1 months in the eribulin group.
Twelves cautions against putting too much emphasis on that finding, given that there were only about 10 women in the standard treatment group.
Side Effects of Eribulin
About 4% of women taking eribulin developed a potentially life-threatening condition called febrile neutropenia marked by infection, fever, and low white blood cell count. That was about three times the rate of women in the other group.
But overall, the rate of serious side effects was similar in both groups, affecting about one in four women.
The most frequent side effects with eribulin were fatigue, weakness, low white blood cell count, hair loss, and nausea, Twelves says. "The key thing is that only 4.8% of women actually had to stop treatment [due to side effects].
Eric Winer, MD, of Dana-Farber Cancer Institute in Boston, tells WebMD that women need to discuss the risks and benefits of eribulin with their doctors.
"There aren't many drugs that show a survival advantage in this setting," says Winer, who moderated a news briefing on the findings.
"I don't know that there are going to be many more chemotherapy agents approved for women with breast cancer," he says, referring to the fact that most of the newer breast cancer drugs like Herceptin and Tykerb target specific molecular defects that fuel different types of tumors.
"That said, this may be one of the last, and potentially provide women with an additional option and maybe an option to be used in combination with targeted therapies in the future," Winer says.
The drug recently received a priority review for approval by the FDA. No price has been set, according to a company spokesperson.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.