As doctors around the world try to find better treatments for glioblastoma, the aggressive type of cancer that attacked Senator John McCain’s brain, eight patients at MUSC Health are taking part in a national clinical trial testing a virus as a possible treatment.
“We want people to know there is hope,” says David Cachia. He’s a neuro-oncologist, which means he diagnoses and treats people with brain cancer and other tumors of the nervous system. He’s leading the Medical University of South Carolina’s part of the trial. “We’re making strides in trying to understand glioblastoma tumors and developing new treatments that will help our patients.”
The virus trial, called Toca 5, is one of three studies Cachia is involved in at MUSC testing possible treatments for glioblastoma. The other two are focusing on medications.
Glioblastoma is the most common type of malignant brain tumor. It can grow to the size of a golf ball in just a few weeks. “It’s often fatal, unfortunately,” Cachia says. “For glioblastoma, the average survival is between 14 to 16 months with treatment. Just over a year.”
But Cachia, who’s part of MUSC Hollings Cancer Center’s brain and spine tumor team, says the more researchers learn about cancer, the better they become at attacking it. “If you understand how and what these tumors are doing at the cellular level it allows us to design drugs and mechanisms of action that stop those cells from replicating when they shouldn’t be doing that.”
The virus trial, which has been open at MUSC for the last three years, is in its third and final phase. The Food and Drug Administration awarded the treatment breakthrough status last year. That expedites the development and review process for promising drugs that may help treat serious health problems. MUSC is the only institution in South Carolina that is taking part in this national trial. It’s funded by Tocagen, the company that makes the treatment.
That treatment involves two parts. First, when a patient has surgery to remove a brain tumor, doctors inject a virus into the brain. The virus has been modified in the lab so it’s harmless to the patient but carries a gene that doctors hope will be harmful to the cancer.
The virus then spreads to infect any glioblastoma cells left after surgery. A few weeks, later the patients are given a drug normally used to treat fungal infections. Once this drug gets into the brain, the gene that the virus carries converts it to chemotherapy, killing the glioblastoma cells.
Cachia said the immune system may also be triggered in the process, helping it recognize cancer cells as the destructive agents they are and attack them. That would put the treatment in the category of immunotherapy. “Long term, this might be the most important aspect of the treatment. If the immune system recognizes the tumor cells, it can potentially sustain that immune response long term, preventing the tumor from growing back.”
The people taking part in the trial have all received other treatments for their glioblastoma, including radiation and chemotherapy, only to have it to grow back. “The average survival for patients who have recurrent glioblastoma is probably six to nine months,” Cachia said.
He said some of the people in the Toca 5 study have survived for three years with no evidence the disease is coming back but cautions against assuming it will work for everyone. “In phase one, the numbers are small. You want to see on a bigger scale what the trend is.”
Phase one tests whether the treatment is safe on a small number of people. Phase two builds on that, and phase three tests the treatment on a much bigger number of people — 380 across the country in the case of the Toca 5 trial.
Cachia said the study shows how cancer treatment is evolving as researchers use technology and previous trials to examine the disease at the cellular level. “We’re going deeper and deeper into understanding these tumors. I think that’s what has made such a difference.”