For centuries, viruses have wreaked havoc on human lives.
In 1916, the polio virus killed approximately 6,000 Americans and paralyzed thousands more.
HIV, the virus that causes AIDS, has killed 39 million people worldwide since the virus was first discovered in humans. Measles has historically been a leading cause of childhood death; before widespread vaccination, measles killed more than 2.5 million people per year. And while the common cold rarely leads to death, it causes plenty of suffering and misery for millions of people on a regular basis.
Yet new research shows that the same potency that makes these viruses such a threat to humans might also be the key to using them as a weapon against an even mightier foe: cancer.
Using Viruses to Kill Cancer
The idea of using viruses to attack cancer dates back more than 100 years. Viruses are extremely good at invading and killing living cells, and cancer is essentially a disease of the cells. Cancer occurs when cell division goes haywire and cells continue to divide and fail to mature. But figuring out how to exploit viruses’ strength–their ability to enter and kill cells–without harming the human body is no easy feat.
Genetic engineering is helping scientists solve that problem. Scientists have figured out ways to genetically alter certain viruses so those viruses only harm cancerous cells. The presence of the virus in cancer cells attracts the attention of the immune system, which mounts an attack designed to destroy the virus. Because the virus is inside the cancer, the cancer is destroyed as well.
Scientists at Duke University, the University of Pennsylvania, the Mayo Clinic and elsewhere have had success using genetically re-engineered viruses to kill cancer cells in people with rare brain cancers (specifically, glioblastoma) as well as blood cancers, including a type of leukemia. Genetically re-engineered viruses have also been used in women with ovarian cancer.
In some cases, results have been dramatic: Patients who were not expected to survive, because their cancers had recurred and resisted regular cancer treatments, later showed no evidence of cancer whatsoever. In other cases, the results have not been as successful. Some patients have died during tests of viral treatments for cancer.
Still an Experimental Treatment
The use of viruses to treat cancer in human beings is still experimental. Right now, scientists and physicians are trying to figure out how to safely use re-engineered viruses to treat cancer. They are testing this approach in small numbers of people to determine safe doses and to learn more about the results and side effects of treatment.
Because viral therapy is still so new, it is only available to patients via clinical trials. A clinical trial is a carefully conducted research study; such trials are used to determine effective dosages, side effects and overall effectiveness of treatment.
Patients are not eligible for a clinical trial of a viral treatment unless traditional treatment has already failed to control the cancer. Traditional cancer treatments, including surgery, chemotherapy, radiation and other approved medications, already have a proven track record of safety and efficacy. New treatments, including viral therapy, have to go through extensive testing (and prove to be at least as safe and effective as currently approved treatments) before being approved for general use.
Patients and families who are interested in learning more about available clinical trials of virus-based treatments for cancer should talk to their physicians. The National Institutes of Health also maintains a searchable list of active clinical trials at clinicaltrials.gov.