Brain Tumors: Primary - Other Treatments

Other Investigative Agents

Retinoids. Retinoids are vitamin A derivatives and act as differentiating agents in cancer treatments. That is, they can convert immature, dividing tumor cells into mature cells, stopping tumor growth. Studies suggest that they have little benefits as single agents. Combination with radiotherapy and other drugs may hold promise.

text continues below

Inactivated Viruses. Investigators are finding that certain genetically inactivated viruses, such as the poliovirus or herpesvirus, may prove to be valuable fighters of brain cancers. Such viruses can enter cells and destroy them but do not pose any danger for infection. For example one specially designed herpes virus targets the enzyme thymidine kinase (an enzyme that promotes tumor growth). Some researchers believe that a combination of this virus with retinoids may be effective with few serious side effects. Other viruses are being investigated. A drug based on this model is years away, however.

Immunnotoxins. Agents called immunotoxins use natural toxins to kill malignant brain cells.

Agents that employ diphtheria toxins, including TransMID-107R and DAB(389)EGF), are the first immunotoxins to show some promise. Clinical trials are investigating them for gliomas and metastatic brain cancers. Other toxins under investigation include irofulven (a mushroom toxin) and chlorotoxin (a substance derived from scorpions).

Taurolidine. Taurolidine is a unique agent that prevents tumor formation and growth in animals. An early clinical trial in patients with high-grade gliomas is under way.

Protein-Blocking Drug. Another development is the discovery of a protein called BEHAB (Brain-Enriched Hyaluronan Binding Protein). BEHAB is produced only by invasive glioma tumor cells, not by normal brain tissue or noninvasive tumor cells. Breakdown of BEHAB releases a substance called HABD (hyaluronan-binding domain), which appears to give glioma cells the ability to invade other areas of the brain. Both BEHAB and HABD represent potential targets for new therapies.

Transplantation Procedures and High-Dose Chemotherapy

Chemotherapy destroys not only cancer cells, but also healthy cells, including special blood cells in the bone marrow called stem cells, which are immature cells from which all blood cells develop. Transplantation procedures using bone marrow or stem cells allow high-dose chemotherapy to be administered while protecting blood cells. The procedures are being tested for patients with brain tumors that are responsive to the effects of chemotherapy. A 2003 study, for example, reported long-term survival in some patients, but it is not clear if such rates are any better than other treatments. The procedure has serious, sometimes life-threatening, side effects.

Photodynamic Therapy

Photodynamic therapy employs a special agent (Photofrin) that is absorbed by the tumor and causes the cancer cells to become fluorescent when a laser is directed at them. It is being investigated in late-stage trials in combination with other treatments. A 2003 study reported encouraging results, notably with patients with recurring glioblastoma multiforme. In the study, more than half of these patients survived for at least a year.