Doctors have successfully dropped the first “smart bomb” on breast cancer, using a drug to deliver a toxic payload to tumor cells while leaving healthy ones alone. In a key test involving nearly 1,000 women with very advanced disease, the experimental treatment extended by several months the time women lived without their cancer getting worse.
A warning to hopeful patients: the drug is still experimental, so not available yet. Its backers hope it can reach the market within a year. The treatment builds on Herceptin, the first gene-targeted therapy for breast cancer. It is used for about 20 percent of patients whose tumors overproduce a certain protein. Researchers combined Herceptin with a chemotherapy so toxic that it can’t be given by itself, plus a chemical to keep the two linked until they reach a cancer cell where the poison can be released to kill it.
This double weapon, called T-DM1, is called the “smart bomb.” Doctors tested T-DM1 in 991 women with widely spread breast cancer that was getting worse despite treatment with chemotherapy and ordinary Herceptin and found that T-DM1 caused fewer side effects than the other drugs did. “People don’t lose their hair, they don’t throw up. They don’t need nausea medicines, they don’t need transfusions,” said Blackwell, who has consulted in the past for Genentech, the study’s sponsor.
“The data are pretty compelling,” said Dr. Michael Link, a pediatric cancer specialist at Stanford University who is president of the American Society of Clinical Oncology, the group hosting the Chicago conference where the results were being presented. “It’s sort of a smart bomb kind of therapy, a poison delivered to the tumor … and not a lot of other collateral damage to other organs,” he said. Dr. Louis Weiner, director of Georgetown Lombardi Comprehensive Cancer Center, said the results strongly suggest T-DM1 improves survival. It delivers more drug directly to tumors with less side effects, “a clear advance,” he said.