New Pancreatic Cancer Treatment Activates Immune System
In Early Study, Strategy Shrank Tumors in Some Patients
Pancreatic Cancer Treatment: Study Details continued...
To put the results in perspective, Vonderheide says that ''the response rate for gemcitabine alone is 5%, one out of 20. In a study this size [with the 21 patients] we would have expected one to have a response."
The median time for progression-free survival was 5.6 months (half longer, half less). The median overall survival time was 7.4 months.
In comparison, gemcitabine alone produces a median progression-free survival of 2.3 months and a median overall survival time of 5.7 months.
One surprise: the researchers thought the antibody treatment would activate white blood cells known as T cells to attack the tumor. But the treatment actually turned on another kind of white blood cells called macrophages.
The study was funded by the Abramson Family Cancer Research Institute, the National Cancer Institute and Pfizer Corp., which makes the antibody.
Pancreatic Cancer Treatment: Future and How It Works
Although the results are encouraging, Vonderheide says ''we have a lot of work to do.'' It will require several years of study and development before the approach is available, he says.
The concept reflects new understanding about cancer cells and what they need to thrive. "It's often thought that if you take out the tumor, 100% of what you take out is cancer cells, but that's not true," he tells WebMD. "A small part of the dense tumor is cancer; the rest of the material is this scaffolding, which the tumor uses to grow."
The tumors rely on this surrounding tissue for blood flow and for a defense against the immune system.
The antibody, he says, activates the immune system in other tissues outside the scaffolding, such as the lymph nodes and the spleen. These activated white blood cells then travel to the scaffolding around the tumor and destroy it.
''Without the scaffolding, the tumor cells don't survive as well," he says.
Pancreatic Cancer Treatment: Perspective
The effect of the treatment is small but important, Phelps says. "In pancreatic cancer, any effect is remarkable. The fact that he sees even in a small study some benefit is pretty remarkable."
The treatment approach reflects recent discoveries about how cancer grows, he says. "We've come to understand in the last three to five years that the somewhat normal cells that surround the tumor play an important role in allowing the tumor cell to grow. The environment of the tumor makes a difference."