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Ibrutinib (Imbruvica) reduced the risk of cancer progression or death by 80 percent when combined with a chemotherapy drug called bendamustine (Treanda) and a targeted therapy drug called rituximab (Rituxan), compared to the other two drugs being used on their own, the researchers found.
"We found that if you add ibrutinib to the standard regimen, progression-free survival was significantly improved as a direct result of the ibrutinib," said lead author Dr. Asher Chanan-Khan, a professor of medicine at the Mayo Clinic in Jacksonville, Fla.
Meanwhile, the second drug, obinutuzumab (Gazyva), helped double the average length of remission for patients with slow-growing forms of non-Hodgkin lymphoma.
"Unfortunately, there is yet no cure for indolent lymphoma, so the overall goal of treatment is to increase the amount of time patients remain symptom-free and in remission," said study author Dr. Laurie Helen Sehn, an oncologist at the BC Cancer Agency in Vancouver, Canada. "The fact that this new approach doubled average remission time marks a major step forward for our patients."
There's no cure for either cancer, so the main goal of therapy is to put patients into remission and keep them in remission as long as possible, Chanan-Khan said.
Both findings were to be reported Saturday at the American Society of Clinical Oncology annual meeting, in Chicago. The data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
The ibrutinib trial involved 578 patients with recurring chronic-lymphocytic leukemia. They were randomly assigned to receive either the usual two-drug treatment, or ibrutinib alongside the standard treatment.
Ibrutinib works by interfering with the messaging signals that CLL requires to survive and proliferate, Chanan-Khan explained. It comes in a capsule taken by mouth once daily.
Patients' chances of entering remission increased if they received ibrutinib by about 83 percent compared with 68 percent for standard therapy, Chanan-Khan said.
People who took ibrutinib also enjoyed longer periods of remission. After 18 months of follow-up, about 79 percent of patients who responded to ibrutinib remained in remission, compared with 24 percent who received standard combination therapy, according to Chanan-Khan.
Finally, the addition of ibrutinib reduced patients' risk of death during the study. "If you look at the survival curve, the chance of dying from the disease, ibrutinib decreases it by 37 percent," he said. "That's pretty steep."
And while patients faced side effects from all three cancer drugs, the researchers found that no new side effects emerged from combining the medications.
The obinutuzumab clinical trial included 396 patients with various types of slow-growing non-Hodgkin lymphoma, researchers said.
Obinutuzumab targets a protein on cancerous white blood cells, causing the cells to either die or become more sensitive to chemotherapy.
Patients were randomly assigned to receive just the chemotherapy drug bendamustine, or a combination of bendamustine and obinutuzumab.
After an average follow-up of 21 months, progression-free survival was 14 months for bendamustine alone versus 29 months for the combination therapy, the investigators found.
"I don't think either one of these drugs are game changers. But these two studies do add weight to the promise they may hold when used in combination therapy for each disease," said Dr. Merry Jennifer Markham, an assistant professor of hematology and oncology at the University of Florida, Gainesville.
Ibrutinib could be added to the existing front-line combination therapy for newly diagnosed CLL, if future research confirms these findings, Markham said. The drug has already been approved by the U.S. Food and Drug Administration, but only for CLL patients who have had one prior treatment.
On the other hand, "obinutuzumab is unlikely to become a standard front-line therapy based on this current study," Markham said. She noted that rituximab still holds the title as the standard targeted up-front therapy for slow-growing non-Hodgkin lymphoma.
Both drugs are expensive and likely to increase the cost of therapy, Chanan-Khan pointed out. "When we load things onto an existing platform of treatment, it will jack up the cost. That is always the case," he said.
"On the other hand, ibrutinib is capable of putting patients into extended remission," he added, noting that CLL patients he used to see once a month now come in annually. "If a person goes into remission and stays in remission for a longer time, then what is the cost for that?"
The ibrutinib study received funding from Janssen Research & Development. And the obinutuzumab study received funding from Genentech and Hoffmann-La Roche.
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