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Thu September 12, 2013
Why Painting Tumors Could Make Brain Surgeons Better
Originally published on Thu September 12, 2013 4:58 am
Perhaps one of the most uncomfortable things a doctor has to tell patients is that their medical problems are iatrogenic. What that means is they were caused by a doctor in the course of the treatment.
Sometime these iatrogenic injuries are accidental. But sometimes, because of the limits of medical technology, they can be inevitable. Now, a medical researcher in Seattle thinks he has a way to eliminate some of the inevitable ones.
James Olson is a physician at the Seattle Children's Hospital, where he primarily takes care of kids with brain cancer. He's also a cancer researcher at the Fred Hutchinson Cancer Research Center in Seattle.
MRI reveals the location of a brain tumor. But it's one thing to see the tumor in a scan, quite another to find the tumor in a living brain. Olson says that today, surgeons splay open the brain in an effort to find exactly where the tumor is.
Just doing that can cause problems. And the surgeons can't always tell tumor cells from healthy brain cells, so inevitably the thorough doctors remove some healthy cells too.
The result is that many times a patient's tumors are successfully removed, but the child is left with movement problems or memory problems or vision problems.
About a decade ago, Olson set out on a search for a something that would make it easier for surgeons to find and remove tumors. What he came up with was a product he calls Tumor Paint.
Tumor Paint is a molecule that consists of two parts. One is a chlorotoxin, a kind of protein that can attach itself to chloride channels on a cell surface. The other is a dye that will fluoresce when you shine a light on it.
It turns out the chlorotoxin in Tumor Paint particularly likes the chloride channels on the surface of tumor cells. So if you inject the paint into a cancer patient's bloodstream, it will attach itself to the tumor.
This means the tumor can be made to glow during surgery, making it easier for the surgeon to find and remove. It should also make less invasive surgery possible. (Here's a short video about how Tumor Paint might work.)
"We think that Tumor Paint might allow surgeons eventually to do a keyhole surgery like you would do for fixing a knee or for removing an appendix," says Olson. "We think they won't have to split the brain open and retract it," he says, thereby eliminating many of the iatrogenic injuries.
One piquant aspect of this new approach: The chlorotoxin in the paint was derived from scorpion venom.
The first tests of the experimental product in human patients are set for later this year.
Olson's isn't the only approach to making tumors light up during surgery. Investigators in Germany have a method of making ovarian cancers glow during surgery. Other researchers in San Diego have used antibodies to a molecule that is on the surface of gastrointestinal tumors to make them glow.
And David W. Roberts, a surgery professor at Dartmouth's Geisel School of Medicine, says he and several others are testing the naturally fluorescent compound 5-aminolevulinic acid (5-ALA), which attaches itself to glial tumors. Roberts sees a bright future for these new imaging techniques that can be done during surgery. "It's a hot field," he says.
This story was produced by Rebecca Davis.
STEVE INSKEEP, HOST:
A medical researcher in Seattle has invented a molecule that can seek out cancerous tumors and make them glow. As part of his series Joe's Big Idea, NPR's Joe Palca explores why this molecule called tumor paint can make an enormous difference in the lives of children with brain tumors.
JOE PALCA, BYLINE: It's tumor clinic day, and Jim Olson is zipping down the hall on the top floor of Seattle's Children's Hospital. I'm doing my best to keep up. We enter a small, windowless room.
JIM OLSON: You can see what a hubbub and bustly it is.
PALCA: This is where the pediatric cancer team gathers before seeing patients.
OLSON: We're going to see Carver, who is a patient that normally Corey takes care of, and this is going to be my first time seeing Carver.
PALCA: Olson is a cancer researcher, but he's also on the team taking care of Carver.
OLSON: He's a boy with a retinoblastoma, the most common type of pediatric brain cancer.
PALCA: Carver had surgery about 15 months earlier to remove his tumor. Olson leans over nurse Corey Hoeppner's shoulder to get a better look at the image on her screen.
OLSON: This is his first MRI scan to follow-up after his therapy, and it's always a nerve-wracking one for the families to be wondering what it's going to look like.
INSKEEP: Olson studies the scan for a few seconds, then heads down the hall. He enters an examining room, where Carver is sitting quietly on a stool next to his mother.
OLSON: Hi, Carver. I'm Dr. Olson. I'm going to see you today.
PALCA: Carver is a pale young boy with hair slicked into a mohawk.
OLSON: We have really good news for you, first and foremost.
CARVER: No brain tumors?
OLSON: No brain tumor.
INSKEEP: So the surgery and chemotherapy are working.
OLSON: All right. Here's where your brain tumor used to be. Look at how nice and clean that looks.
INSKEEP: But as good as the good news is about the cancer, Carver still has serious health problems.
OLSON: So, since your last visit here, what are the things that you're most worried about?
CARVER: Well, I guess what people think of my eye, and maybe I won't be able to run and jump like everyone else. And - sorry, what was the question?
OLSON: That's OK. No worries.
PALCA: Carver's short-term memory is a mess, and he has difficulty walking. His eyes haven't been pointing straight since his tumor was removed. That'll take more surgery to fix. None of these problems was caused by Carver's cancer. They're the result of the surgery to treat his cancer. What happened? Well, first of all, the surgeons didn't do anything wrong. The problem is, right now, they have to splay open the brain to find exactly where the tumor is. Just doing that can cause problems. And once they find the tumor, they want to remove all of it. But Olson says, to the naked eye, cancer cells don't look all that different from healthy brain cells.
OLSON: It's not like some alien that comes into our body. It's normal cells that are just dividing more rapidly than other cells.
PALCA: So, inevitably, surgeons wind up removing some healthy cells, and that can cause problems, too. Olson truly appreciates what surgeons do. Still, it really bothers him that even successful cancer treatments are likely to cause children harm. But as he explained to Carver, Jim Olson thinks he's found a way to minimize these problems.
OLSON: Our lab invented a molecule that will help kids that have to go through your kind of surgery in the future. And this is a molecule that we call tumor paint.
PALCA: Tumor paint is a molecule that consists of two parts. One is a protein that can go into the bloodstream and, all by itself, find the cancerous tumor. The other is a fluorescent dye. So when a surgeon shines a light on the tumor, it glows.
OLSON: Tumor paint, believe it or not. Guess where it came from?
CARVER: Scorpion venom?
OLSON: Oh, you already know the answer, don't you?
PALCA: Nearly everybody at Seattle Children's Hospital knows about tumor paint. Olson's a good pitch man. Why scorpion venom? Well, it's a long story, but the short answer is that if you modify scorpion venom in just the right way, you get something that sticks to cancer cells. It certainly sounds like a promising approach, but Olson told me when he first applied to funding agencies to get the tumor paint project going, they all turned them down.
OLSON: In every case, the answer that came back was this is overly ambitious. This is highly speculative. It may not work in the timeframe of the grant. And my thought was come see my patients. We need people to be overly ambitious. You should be giving me money because I'm overly ambitious, and because you want me to be speculative and you want to take a quantum leap in this disease, and not because you want to take a baby step.
PALCA: So, to develop tumor paint, he turned to the families of patients he treated.
OLSON: The kids made greeting cards and sold them, and the families had golf tournaments and auctions and chili cook-offs. And $100 at a time, they raised about $8 million, and that funded tumor paint development.
PALCA: Tumor paint is now well along in its development, but Olson continues to turn to his patients and their families to support his research.
OLSON: OK, good. Why don't you come down off the table?
PALCA: I got a firsthand look at how Olson recruits new supporters when he spoke to Carver after he finished the exam.
OLSON: I'd like to invite you and your family and your friends to come over to the lab and meet the scientists and...
CARVER: That'd be cool.
OLSON: ...take a look at some of the brain tumor cells under the microscope.
PALCA: Jim Olson hopes it won't be too long before tumor paint can be used in children like Carver, so their successful surgery won't leave them with memory problems and walking problems and eye problems. Studies of tumor paint in human patients are set for later this year. Oh, yes. I'm happy to report that Carver's cancer treatment does not appear to have affected his sense of humor.
CARVER: Where's the dog with no legs?
CARVER: Right where you left him.
PALCA: Joe Palca, NPR News.
CARVER: Oh, what's a boomerang that doesn't come back to you?
PALCA: A rock.
CARVER: A stick.
PALCA: That's great. I like that one.
RENEE MONTAGNE, HOST:
Now, tomorrow, Joe's Big Idea explores the mind and motivation of Jim Olson: innovator, creative thinker and physician. Transcript provided by NPR, Copyright NPR.