An experimental drug treatment may help keep a certain kind of aggressive breast cancer at bay, offering new hope for individual therapies against difficult tumours, said research released Sunday.
The phase III trial comparing trastuzumab emtansine (T-DM1) to standard therapy for human epidermal growth factor receptor 2 (HER2 positive) breast cancer was presented at the American Society of Clinical Oncology conference in Chicago.
The international study randomized nearly 1,000 patients to receive either T-DM1 or standard therapy every three weeks. The subjects all had metastatic cancer that had spread to other parts of the body.
The trial found that progression-free survival in the T-DM1 group was 9.6 months, compared to 6.4 months in the standard therapy group, which study authors described as “clinically meaningful improvement.”
“The drug worked. It was significantly better than a very effective approved therapy for HER2 overexpressing metastatic breast cancer,” said lead study author Kimberly Blackwell, professor of medicine at Duke University.
“Also, as a clinician who takes care of a lot of breast cancer patients, I’m pleased that this drug has very little dose-limiting toxicity. Patients don’t lose their hair from this drug.
“For patients facing metastatic breast cancer, this is a breakthrough.”
The data on overall survival time showed 65 percent of T-DM1 patients were alive after two years, compared to 47.5 percent of the standard therapy patients, a threshold that fell short of the trial’s predetermined limits for judging statistical significance.
More analysis of survival times is planned for later in the ongoing study.
HER2 positive cancer makes up about 15 percent of breast cancers, and is tends to be more difficult to treat. However some targeted therapies have shown promise, such as trastuzumab, also known as Herceptin.
“Trastuzumab is now a standard in the adjuvant setting to reduce risk of recurrence and improve survival, and in the metastatic setting to control disease and prolong life,” said Antonio Wolff, professor of oncology at The Johns Hopkins Kimmel Cancer Center.
“Unfortunately, there are still many patients with HER2-positive disease whose disease recurs despite adjuvant trastuzumab, and whose cancers stop responding when treated in the metastatic setting,” said Wolff, who was not involved with the study.
He described T-DM1 as a “second generation HER2-targeted therapy that goes one step further” by delivering small doses of chemotherapy to the HER2 positive tumours.
TDM-1 is “another critical step in our quest towards the individualisation of therapies,” he said.
These therapies, like trastuzumab, have “helped change what was once a bad prognosis into a disease that can now be controlled and in many patients cured.”
Wolff said future studies are likely to focus on T-DM1 as a treatment given earlier in the course of the disease, and in combination with other drug treatments.
Trastuzumab emtansine is being developed globally by Swiss pharmaceutical giant Roche under a collaboration agreement between ImmunoGen and Genentech, and drug makers are seeking regulatory approval in the US and Europe this year.