While progress in brain tumor treatment has been slow, new research has the brain cancer community buzzing. Recent work contributing to an understanding of the molecular mechanisms and gene mutations, combined with clinical trials, is leading to more promising and tailored therapeutic approaches.
Immunotherapy is a new modality showing potential in patients who receive a diagnosis of glioblastoma multiforme (GBM)—the most common and most aggressive brain cancer with a strong resistance to conventional therapies and a high relapse rate. In 2014, the American Cancer Society estimates about 23,000 new cases of brain and other nervous system tumors will be diagnosed and that there will be more than 14,000 deaths from these tumors.Immunotherapy can include treatment with monoclonal antibodies, cancer vaccines and other therapies that stimulate an immune response to help the body recognize and attack cancer cells—all with the goal of ultimately shrinking tumors and prolonging lives.
Monoclonal antibodies are synthetic immune system proteins and are quite prolific in cancer treatment now. The monoclonal antibody Avastin (bevacizumab) has been used to treat recurrent or resistant brain cancer since it was approved by the Food and Drug Administration in 2009.
Different forms of immunotherapy already have led to major improvements in the outcomes of some cancers, including resistant HER2-positive breast cancer, lymphomas, leukemias and melanoma. However, malignancies of the brain represent more of an enigma to researchers, resulting in slower adoption of immunotherapies than in other cancers.
While many vaccines are used to prevent diseases, vaccine therapy as a cancer treatment is gaining speed. Provenge (sipuleucel-T), the first cancer therapeutic vaccine, which uses the patient’s own immune dendritic white cells that are “boosted” against a prostate cancer specific antigen, was approved in 2010 to treat advanced prostate cancer. Since then, there has been an abundance of cancer vaccine clinical trials, but no new vaccine has been approved.
“The first thing that a brain cancer has to do in order to grow and be successful to survive and thrive in its human host is to make itself invisible,” says Keith L. Black, chair of the department of neurosurgery at Cedars-Sinai Medical Center in Los Angeles. Secondly, brain cancer works to weaken or suppress the immune system. “It’s a strategy that cancers employ, particularly brain cancer.”
A diversity of cells constitutes a brain tumor, posing additional challenges. Also, “the central nervous system is cordoned by the blood-brain barrier that limits the access of common therapeutic agents,” says Nabil Ahmed, a pediatric oncologist at Texas Children’s Cancer and Hematology Centers in Houston. “Modern immunotherapy has been able to overcome this limitation with some success.” But more potent and personalized agents requiring advanced technology are needed to propel further progress.
It’s a different form of therapy. What we’re trying to do with the brain is not to replace the standard of care, but to add another category of treatment.