Researchers make vaccine from brain tumour, try to stop recurrence
Published: Thursday, November 16, 2006 | 4:59 PM ET
Canadian Press: SHERYL UBELACKER
TORONTO (CP) - Brain tumours known as recurrent gliomas are notoriously difficult to treat and remain among the deadliest of all cancers. But some researchers are trying a different tack - harnessing the tumour itself to create a possible therapy.
Dr. Andrew Parsa, a neurosurgeon from the University of California at San Francisco Medical Center, has helped create made-to-measure vaccines using a person's surgically removed tumour, and he's started testing the concept in a small group of patients.The vaccine, which utilizes specific proteins from the tumour, is administered through a needle to the arm every two weeks, with the aim of stimulating T-cells from the immune system to attack any regrowth of the cancer.
"We've now got some compelling data from the first six patients and it looks like clearly all six patients had an immune response," said Parsa, the study's principal investigator. "In other words, when I test their blood after the vaccination, it's apparent that they have T-cells that weren't there before that are specific to their tumour."
"And of those six patients, five of them have lived longer or are living longer than 6.5 months after recurrence of glioblastomas, which is the most malignant kind of brain tumour you can have," Parsa said in an interview from Orlando, Fla., where he presented his findings Thursday at the Society of Neuro-Oncology annual scientific meeting.
Four of the patients have survived almost a year. One woman died about 10 months after starting vaccinations, while the sixth patient died before 6.5 months - the average expected period of survival for this rare form of brain tumour, which arises from the glial cells in tissue that surrounds nerve cells.
High-grade recurrent gliomas, or glioblastomas, can be made up of several different types of cancer cells and may infiltrate many parts of the brain. About 900 Canadians are diagnosed with gliomas each year.
But Parsa stressed that these are extremely preliminary findings, based on a small number of patients in a phase 1 study designed to ascertain safety - not effectiveness.
"It just so happens we have some really dramatic immunomonitoring data and some interesting survival data at this point," he said. "It is too soon to say that this is going to be an effective treatment."
Commenting on the research, neuro-oncologist Dr. Warren Mason of Toronto's Princess Margaret Hospital said various types of experimental immune-stimulating therapies have been tried on brain tumours in the past, all without success.
And while the U.S. researchers did seem to evoke an immune response with their vaccine, "the outcome data - which only involves six patients - is neither here nor there," concluded Mason, who was not involved in the research. "So just because they seem to do better than what's published as historical landmark survival data doesn't mean that anything is actually happening there."
"I don't see any overwhelming evidence here for real enthusiasm."
Still, Parsa said he's encouraged by the initial results. Another six glioblastoma patients are being tested with individualized vaccines to complete the study on safety - this time, with weekly shots - and his team will be recruiting another 48 patients for a phase 2 trial, which will determine the vaccine's effectiveness. That study should begin next year.
Parsa said the initial six patients had undergone multiple treatments and in some cases had multiple recurrences of their cancer. "They have exhausted all other options. There is no current effective standard of therapy for patients who have recurrence of a high-grade glioma after failing conventional chemotherapy and radiation."
"So these are patients who are in desperate need of something and I'm hoping that the vaccine will fill that role . . . And that's what we're all working so hard to try to do."
One of those patients, 66-year-old Rosalind Hekkala of Reno, Nev., was diagnosed with a brain tumour and had it removed in July 2005. A a new tumour was detected that November, despite chemotherapy and radiation. Since beginning injections of her custom-made vaccine almost a year ago, no new cancer has appeared, she said.
"My last MRI looked really good," Hekkala said of her brain scan a week ago. "I'm feeling very confident about it and I feel stronger all the time."
To create the vaccine, Parsa teamed with biotech company Antigenics Inc. of Massachusetts. The California neurosurgeon, who also holds a PhD in immunology, said he has no financial connection of any kind with the company. The US$250,000 funding for the research was provided by the American Brain Tumor Association through the National Cancer Institute.
"Cancer vaccines have come and gone over the years," Parsa said, "and I think the reason they've come and gone is that we haven't put enough thought into applying them to the right patients and we haven't put enough thought into carefully documenting the immune response."
作者:admin@医学,生命科学 2011-05-23 05:11