Tiny Radiation Beams Spare Cancer Patients Some Side Effects

Editor's Note: This is the fourth story in a five-part series about clinical research at the University of Nebraska Medical Center. To learn more what clinical research is and the role it plays at UNMC, read the introduction to this series.

OMAHA - With his throat cancer at its worst, Wayne Tobias couldn't even swallow water. After special radiation treatments available only one place in Nebraska, he's eating steak.

Even with his sense of taste deadened temporarily, Tobias has it better than many of the cancer patients who have gone before him. Because his radiation comes in hundreds of tiny beams aimed just at his tumor, he still has something most of us take for granted: saliva. He'd likely have a permanent case of dry mouth with traditional radiation.

He's also still got his voice, and just minutes after his latest treatment at the University of Nebraska Medical Center, he's happy to use it telling just how happy he is about eating steak again.

"It's about like getting my life back," he said. "Makes me think when I get my sense of taste back, I'm really going to enjoy that."

Tobias, 72, drives to Omaha from Hastings regularly to receive Intensity Modulated Radiation Therapy, a leap forward in cancer treatment available at just 80 hospitals nationwide, and just UNMC in Nebraska. The terrifically expensive and powerful machine doesn't aim a single-strength, wide beam of radiation at the tumor as in traditional therapy -- which hits and damages healthy tissue in the process. Instead, computers analyze a CAT scan of the cancerous area and figure out ways to fire hundreds of very narrow, but very powerful, beams that dodge critical healthy structures around the tumor. Like Tobias' salivary glands, voice box and -- most importantly -- his spinal cord.

"Our goal is always to deliver radiation where you can have better targeting, and spare more normal tissue," said Dr. Ken Zhen. He's one of the most experienced hands with the IMRT, having started using it in Iowa in 1998, just one year after the Food and Drug Administration approved it. He came to UNMC in 2000.

Zhen and his colleagues in radiation oncology are doing clinical research to determine how well the IMRT technique works. It's slow going; doctors need to wait 2-3 years to definitely see whether patients are cured, or suffer recurrences. Most of the data so far are on cancers in the head and neck areas, because it's easy to immobilize that part of the body. Just a tiny bit of movement can put that salivary gland you were hoping to avoid right in the path of a destructive beam.

Conversely, there's little data on using IMRT against moving targets -- such as the prostate gland, which shifts position based on bowel and bladder contents, even respiration. But another, even newer technology at UNMC is solving that problem. Called BAT, for B-mode Acquisition and Targeting, this new machine uses ultrasound imaging to find the prostate gland, then spits out a bunch of numbers that are punched into the treatment table to position the patient just so for his radiation therapy. In a great improvement for patient comfort, the ultrasound wand is applied externally to the lower abdomen, instead of inserted into the rectum.

Dr. Charles Enke is the main man with the BAT machine, which actually is all black with a big stylized bat-wing logo on the front. Men get a metal bat lapel pin when they complete their treatment.

"There is a significant amount of data emerging that indicates that the likelihood of prostate cancer control can be increased by 20 to 40 percent at 5 years by increasing the prostate dose over standard radiation doses," Enke said.

BAT works in concert with IMRT to help direct radiation beams around two critical structures near the prostate, the rectum and the bladder. The rectum's especially sensitive, and too much radiation can create a hole in it. That sentences patients to the inconvenience of a colostomy bag, external storage for the body's solid waste. Damaging the bladder can require an external bag to collect urine.

After treating 61 patients with BAT, Enke has found he can apply radiation doses of 7,600 to 7,800 rads, instead of the 6,800 to 7,100 rads many radiation therapy centers must use to avoid dangerous side effects.

Traditional therapy uses marks on the skin to indicate where the prostate was when doctors first located it and applied the initial radiation does. But preliminary results from a study Enke is conducting indicate the prostate may move as much as 10.4 millimeters from this location. Using the BAT machine, he's found, can reduce uncertainty about the prostate's location to 1 or 2 millimeters.

IMRT, with assistance from BAT in some cases, doesn't just make it possible to dodge healthy tissue. Doctors can also direct more powerful radiation at the tumor, the better to kill it faster. Think back to traditional radiation for throat cancer. Compared with IMRT, it's like putting fire hoses on both sides of your face and turning them on full blast. Sure, the tumor in the middle of your throat gets a full dose of radiation, but so do your salivary glands and spinal cord, because the radiation has to pass through those structures on its way to the spinal cord. So you have to limit the radiation sent to the tumor, because surrounding tissue can only withstand so much abuse. But with IMRT, which is like a very fine stream, you can send a tremendously powerful jet into the tumor because it's targeted to miss the parts you want kept alive. As the radiation emitter rotates around the patient, these tiny beams eventually stab through all parts of the tumor. (All this careful precision means IMRT treatment takes 30-40 minutes per treatment, while conventional therapy takes just 15 minutes.) If the fire hose and fine stream examples don't work for you, think of it this way: On a stage with 200 performers, you could light them all with one huge lamp. Or, you could use 200 spotlights , varying the color and intensity of each light to create a pleasing effect.

The idea behind IMRT therapy has been around for 20 years, Zhen said, but had to wait for computer technology to catch up with it. Medical physicist Ayyangar Komanduri explained that traditional radiation therapy can be planned with pen and paper, because there are just a few parameters to compute. But it's nearly impossible to analyze complex body scans and plot hundreds of precise coordinates without a computer's help.

"It's like trying to manage a bank account with several investors in place," Komaduri said. "How would you manage that without putting it into an accurate spreadsheet?"

For Tobias, the Hastings throat cancer patient, it's not just all this fantastic technology that's made the difference in his recovery.

"They've been wonderful people up here," he said. "They treat you like you're Warren Buffett or somebody."

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This story originally appeared in Nebraska StatePaper on July 26, 2001.