Doctors Test Tumor Paint In People
A promising technique for making brain tumors glow so they'll be easier for surgeons to remove is now being tested in cancer patients.
Eighteen months ago, Shots first told readers about tumor paint, an experimental substance derived from scorpion venom. Inject tumor paint into a patient's vein, and it will actually cross the blood-brain barrier and find its way to a brain tumor. Shine near-infrared light on a tumor coated with tumor paint, and the tumor will glow.
The main architect of the tumor paint idea is a pediatric oncologist named Dr. Jim Olson. As a physician who treats kids with brain cancer, Olson knows that removing a tumor is tricky.
"The surgeons right now use their eyes and their fingers and their thumbs to distinguish cancer from normal brain," says Olson. But poking around in someone's brain with only those tools, it's inevitable surgeons will sometimes miss bits of tumor or, just as bad, damage healthy brain cells.
So Olson and his colleagues at the Fred Hutchinson Cancer Center in Seattle came up with tumor paint. They handed off commercial development of the compound to Blaze Bioscience.
After initial studies in dogs showed promise, the company won approval to try tumor paint on human subjects. Those trials are taking place at the Cedars Sinai Medical Center in Los Angeles.
Dr. Chirag Patil is one of those surgeons. He says it's remarkable that you can inject tumor paint into a vein in a patient's arm, have it go to the brain and attach to a tumor, and only a tumor. "That's a concept that neurosurgeons have probably been dreaming about for 50 years," he says.
An image of a mouse brain tumor under near-infrared light. The blue-green glow in the upper right quadrant is the tumor, labeled with tumor paint.
Patil says they've now used tumor paint on a about a half-dozen patients with brain tumors. They use a special camera to see if the tumor is glowing.
"The first case we did was a deep tumor," says Patil. "So with the camera, we couldn't really shine it into this deep small cavity. But when we took that first piece out and we put it on the table. And the question was, 'Does it glow?' And when we saw that it glows, it was just one of those moments ...'Wow, this works.' "
In this first study of tumor paint in humans, the goal is just to prove that it's reaching the tumor. Future studies will see if it actually helps surgeons remove tumors and, even more important, if it results in a better outcome for the patient.
That won't be quick or easy. Just getting to this point has been a long slog, and there are bound to be hurdles ahead.
And even if tumor paint does exactly what it's designed to do, Dr. Keith Black, who directs neurosurgery at Cedars-Sinai, says it probably isn't the long-term solution to brain cancer. "Because surgery is still a very crude technique," he says.
Even in the best of circumstances, Black says, surgery is traumatic for the patients, and tracking down every last cell of a tumor is probably impossible. Plus, it's inevitable that some healthy brain tissue will be damaged in removing the tumor.
"Ultimately, we want to eliminate the need to do surgery," says Black. A start in that direction will be to use a compound like tumor paint to deliver not just a dye, but an anti-cancer drug directly to a tumor. That's a goal several research groups, including Jim Olson's, are working on.
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Transcript
STEVE INSKEEP, HOST:
A few years ago, NPR's Joe Palca first introduced us to a group of medical researchers in Seattle. They were working on what is called tumor paint - glowing paint. A glowing tumor would be easier for surgeons to see and remove. Researchers were trying to modify scorpion venom so that it would stick to brain tumors and make them glow. Today, Joe checks back in on this project as part of a series, Joe's Big Idea.
JOE PALCA, BYLINE: The main architect of the tumor paint idea is Jim Olson. He's a researcher who also takes care of kids with brain cancer. Olson knows removing a tumor is tricky.
JIM OLSON: The surgeons right now use their eyes and their fingers and their thumbs to distinguish cancer from normal brain.
PALCA: Olson says poking around in someone's brain with only those tools, it's inevitable surgeons will sometimes miss bits of tumor or, just as bad, damage healthy brain cells.
OLSON: There's got to be a way to help the surgeons have a more clear understanding of what is cancer and what is not cancer.
PALCA: The better way, he and his colleagues at the Fred Hutchinson Cancer Center in Seattle came up with, was tumor paint. Turns out, there's a compound in scorpion venom, of all things, that attaches to cancer cells and only cancer cells. Combine that compound with a fluorescent dye and when you shine a special light on a tumor covered with tumor paint, it glows. Olson tested the idea on tumors grown in the lab, and it seemed to work. But would it work in patients? The answers are coming from patients like Sydney.
It's OK, Sydney.
(SOUNDBITE OF DOG WHIMPERING)
PALCA: Sydney is a Brittany spaniel. She had cancer and needed surgery. I caught up with veterinarian Katie Kennedy as she was about to operate on Sydney. The cool thing about tumor paint is you can inject it into a vein, and it will find the tumor all by itself and attach to it. In this operation, Kennedy's goal was to see if the tumor paint gets to Sydney's tumor and makes it glow. I asked her how she normally distinguished healthy tissue from tumor tissue.
KATIE KENNEDY: Normally, we don't. You know, we can visually see the gross tumor, of course, but we know that there's microscopic cells that are extending out from that tumor. And we never know how far those tendrils are really spreading to make that tumor grow.
PALCA: And I know you have to run, but you think it's a good idea, or you think it's going to work?
KENNEDY: Oh, I think it's amazing. I think it's the forefront of science, and it's incredibly exciting for me to be part of it.
PALCA: Kennedy and her colleagues start the operation and watch eagerly to see if the tumor lights up.
That's all tumor paint, right?
KENNEDY: That's all tumor paint.
Hey guys, are you catching this image?
PALCA: Kennedy says Sydney's surgery went well, and the tumor paint seems to be attaching to tumor cells as advertised. Now, showing it works in dogs is one thing, showing it works in humans - that's another. That's what surgeons at Cedars-Sinai Medical Center in Los Angeles are trying to do. Chirag Patil is one of those surgeons. He says the idea that you could inject something into a vein in a patient's arm and have it go to the brain and attach to a tumor and only a tumor...
CHIRAG PATIL: That's a concept that I think neurosurgeons have probably dreaming about for 50 years.
PALCA: Patil says they've now used tumor paint on a handful of patients with brain tumors. They use a camera to see if the tumor is glowing.
PATIL: The first case we did was a deep tumor, so with the camera, we couldn't really shine it into this deep, small cavity. But when we took that first piece out and we put it on the table, and the question was, hey, does it glow? You know, when we saw that it glows, it was just one of those moments - wow, this works.
PALCA: In this first study of tumor paint in brain cancer patients, the goal was to prove it's reaching the tumor. Future studies will see if it actually helps surgeons remove tumors and helps patients live longer. Answering those questions won't be quick or easy. Just getting to this point has been a long slog. But even if tumor paint does exactly what it's designed to do, Keith Black doesn't think in the long-term it's a solution to brain cancer.
KEITH BLACK: Because surgery is still a very crude technique. We have to make an incision in the scalp. We have to, you know, crack open the person's skull.
PALCA: Black leads the neurosurgery department at Cedars-Sinai and is part of the tumor paint trial. He says even in the best of circumstances, surgery is traumatic for the patients and tracking down every last cell of a tumor is probably impossible.
BLACK: Ultimately, we want to eliminate the need to do surgery.
PALCA: And Black has an idea how to do that - use tumor paint, or something like it, to deliver not just a fluorescent dye but an anticancer drug directly to the tumor. In fact, cancer researchers are working on that very idea now. I'll let you know what happens. Joe Palca, NPR News. Transcript provided by NPR, Copyright NPR.
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