In a study of nearly 300 women, those given the combo lived four-and-a-half months longer than those given Tykerb alone. All of the women in the study had metastatic disease that had continued to spread even after treatments that included Herceptin.
Fifty-six percent of the women were still alive a year after treatment began -- results unheard of in patients with advanced disease who fail Herceptin, Duke University's Kimberly Blackwell, MD, tells WebMD.
The findings were presented at the San Antonio Breast Cancer Symposium.
How Herceptin and Tykerb Work
About 20% of breast cancer patients have HER2-positive cancers -- tumors that have too much of a type of protein called HER2, which promotes the growth of cancer cells. Herceptin blocks HER2 from breast cancer cells.
But metastatic breast cancer eventually becomes resistant to Herceptin. So researchers have searched for new drugs that target HER2.
Tykerb is such a drug. It zeroes in on two related proteins -- HER2 and EGFR -- that play a critical role in the growth and spread of cancer.
"It's sort of a double whammy, disabling the HER2 protein in two places instead of one," Blackwell says.
Tykerb-Herceptin Combo Extends Breast Cancer Patients' Lives
Blackwell and colleagues studied 295 women with metastatic breast cancer, meaning their cancer had spread to other organs.
All had been treated with Herceptin alone or in combination with various chemotherapy drugs but were still were getting worse.
Half the women then got Tykerb; the other half got the Tykerb-Herceptin combination.
Those who got the combination therapy were 26% less likely to die over the course of the study. They lived an average of about 14 months vs. 9.5 months for those who got Tykerb alone.
Adding Tykerb to Herceptin did not worsen the side effects. "As a clinician, I think it’s amazing there was no increase in side effects with the combination of drugs," Blackwell says.
Edith Perez, MD, a breast cancer specialist at the Mayo Clinic in Jacksonville, Fla., tells WebMD that the results of the study have been eagerly awaited.
"In the U.S., there's a tendency of doctors to take women off Herceptin once it fails to help, but this shows significant benefit to continuing with it and adding a second targeted agent," she says. Perez says the combo is now being tested in women with early-stage breast cancer, for whom they expect it to work even better.
The study was funded by GlaxoSmithKline, which makes Tykerb. Blackwell consults for GlaxoSmithKline and for Genentech, maker of Herceptin.
Avastin Fails to Improve Breast Cancer Patients' Survival
Also at the meeting, two large studies showed that adding the targeted drug Avastin to standard chemotherapy modestly delayed the time until advanced cancer got worse but had no overall effect in survival.
That's the $100,000 question, Perez says. She was not involved with the work.
"It's hard to justify giving the drug to all the women. But we would like to offer it to that one in four it might help. We have to wrestle with the issue," she says.
Researchers are now trying to find biomarkers that will help pinpoint which women will benefit from the drugs and which won't, Perez says.