Study shows progress in vaccine development for deadly brain tumor
Glioblastoma is a highly lethal type of tumor. For the majority of patients, survival is often measured in months, not years, particularly after a recurrence. Now, there is a little hope in the form of a vaccine. But local doctors say, not so fast.
The prognosis is poor for patients with the aggressive form of brain cancer.
Dr. Rimas Lukas is a neuro-oncologist with Northwestern Medicine.
“Unfortunately, at this point in time we do not have a cure for the disease,” Lukas said. “And so even if scans look good, we’re working under the assumption that there is residual tumor cells that will grow at some point in time.”
There have been some advancements – most notably a device worn on the scalp that uses electrical fields to slow disease progression.
“When cells are within an electrical field, and they are trying to divide and make more tumor cells, it stops them from dividing and it also kills some of those cells,” Lukas said.
The device – known as tumor-treating fields — has been shown to improve survival and is now considered part of the contemporary standard of care that includes surgery, radiation and chemotherapy. But doctors hope to add to their arsenal of treatments – immunotherapy among them.
“It’s something exciting because the immune system has demonstrated proof of principle of being very effective at treating some highly aggressive cancers, so Stage 4 melanoma now have long-term survivors,” Lukas said.
The idea is to harness the body’s own immune system to seek and destroy cancer cells – often using a patient’s own tumor samples to teach the body what to target. The problem for glioblastoma patients is that the cells vary from one to the next, making them a tricky target.
“Ideally you can have an immune system which can go after this cell type and this cell type and this cell type,” Lukas said.
Scientists are trying to do just that. In a study that began in 2007 – the DCVAX clinical trial – investigators in four countries and at 94 different sites combined patients’ own tumor cells with their white blood cells to stimulate an immune response.
“I do think we need to interpret the results with some degree of caution,” Lukas said.
Instead of comparing two participant groups from within the same clinical trial — those who received the vaccine vs those who did not — the study findings were ultimately compared to data collected from outside the trial – what’s called a historical control.
“So taking an aggregate of information from older studies and seeing how this shaped up in comparison to that,” Lukas said.
Among 331 clinical trial participants, those who received the vaccine – 232 patients – lived about three months longer (19.3 months) than patients who received standard of care – surgery, chemotherapy and radiation (16.5 months)
The study also included those who had a recurrence of the cancer. Survival time in patients who received the vaccine after relapse was 13.2 months compared to 7.8 months in those who did not get the vaccine.
Looking at long-term survival rates, 13 percent of those who received the vaccine were still alive five years after treatment. That’s compared to 5.7 percent of patients who received standard therapy.
Still, Lukas says there’s another caveat to consider. The study authors did not test the vaccine against the scalp device, which has improved median survival to 21 months – that’s two months longer than the vaccine.
“If you compare the results of the vaccine-based trial, they are inferior to the survival outcomes seen in our contemporary standard of care,” Lukas said. “It dampened my enthusiasm to some degree, but it doesn’t negate my interest in still following this avenue of research.”
Lukas says there’s more work to be done when it comes to utilizing immunotherapy in neuro-oncology – they still have to sort out why it’s not as successful as it is in the treatment of other cancers.
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