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Prostate cancer scan advance helps Mayo doctors with early detection

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New imaging agent
Ping Fang, a senior chemist in Radiology at Mayo Clinic, monitors the production of C-11 methyl choline in a lab Wednesday, Nov. 28, 2012 at Mayo Clinic in Rochester, Minn. C-11 choline is an agent used during PET scans to help detect reoccurring prostate cancer. The Mayo Clinic is the only health facility in the U.S. currently approved by the FDA to administer Choline during PET scans, and they plan to expand their production and services to offer it to more patients.
MPR Photo/Jeffrey Thompson

When treating cancer patients who suffer a second bout of the disease, doctors know catching the recurrence soon is crucial to the patient's chances of survival.

But that's been a challenge with prostate cancer, because doctors depend on a test that measures levels of prostate-specific antigen, or PSA, in the blood. PSA is a protein produced by prostate cells, and when men have prostate cancer their levels of the protein are often elevated.

In men with recurrent disease, rising PSA levels can suggest that their cancer isn't cured.

"It's like a puff of smoke that's signifying an early fire," said Dr. Eugene Kwon, urologist at Mayo Clinic who treats patients with advanced prostate cancer.

That's why a new Mayo Clinic scanning technique that helps doctors detect recurring prostate cancers months or even years earlier than before, is receiving considerable attention. The test searches for a common nutrient that all cells, including cancer cells, need to grow.

A MAYO EXCLUSIVE

This fall, Mayo Clinic received approval from the U.S. Food and Drug Administration to use the new imaging agent. It is the only health care provider in the United States that is offering the scan to patients.

• Photos: Go inside Mayo's lab

The scan allows men with cancer to receive treatment that is both faster and potentially more effective than current tests. As a result, patients from around North America have flooded the clinic with requests to use the scan because it's much more sensitive than other available techniques.

The Mayo Clinic books approximately 22,000 prostate cancer visits each year — most of them for men whose cancer has returned.

The problem for doctors and patients is that PSA levels alone don't reveal much, said Kwon, a professor of urology and immunology at Mayo Clinic. Follow-up scans are necessary to actually see where the cancer might be located. But conventional scans aren't sensitive enough to detect early relapse of prostate cancer.

"A lot of times you had to wait until the PSA got very high which made the physician and the patient very uncomfortable," he said.

By that time a recurrent cancer could be widespread and more difficult to treat.

With the Mayo Clinic's new Choline C 11 PET imaging test, Kwon said, the scan results are remarkably detailed — even with small areas of cancer.

"I've seen a single hot spot in the middle of the breastbone," he said. "I've seen a single hot spot behind the eyeball. So instead of guessing you absolutely know what you're dealing with."

The scanning technique uses choline, a common nutrient that all cells, including cancer cells, need to grow, said Dr. Val Lowe, a Mayo Clinic radiologist who convinced the clinic to start using the new technology.

"You're essentially designing a homing beacon," said Lowe, also a professor of radiology.

As prostate cancer cells multiply, they absorb a lot of choline. Lowe said that makes the compound a good biomarker for detecting tumors.

"If a cancer is growing and producing more cells, then the hypothesis is that it's going to need more choline than other tissues around it," he said. 

Before the test, Lowe's team attaches a radioactive isotope to the choline. When the solution is injected into a patient's bloodstream it emits a signal that can be seen on a PET scan.

ONE PATIENT'S STORY

Among those to undergo the test are Larry Weber of Olney, Ill., who was diagnosed and treated for aggressive prostate cancer six years ago. This summer the 58-year-old felt some discomfort after riding his bike. His doctor found a tumor and a biopsy revealed that it was cancerous.

"Not knowing what you're dealing with is worse than knowing what you're dealing with."

Weber doesn't know how widespread the cancer is. That's why he came to Mayo Clinic last week.

"This scan should see all of it," he said. "That's my understanding." 

But as much as Weber wants to know what's going on with his cancer, he also is worried about what the scan will reveal.

"I've got some grandkids I want to rock," he said, his voice cracking with emotion. "That's the deal." 

About 24 minutes after he entered the imaging chamber, Weber's scan was complete. But he wouldn't find out his results until the next morning when he meets with his doctor.

Reached on his cell phone shortly after that visit, Weber was open about his diagnosis. It's not good news.

"The test was comprehensive and it's pointing toward a probably, substantially serious surgery," he said. 

The scan found that cancer has spread throughout his pelvic region. Surgeons want to remove Weber's bladder and bowels. But more troubling than that is the news that there are also some cancerous spots on his lungs.  Chemotherapy may be his only option for extending his life.  

A Christian pastor, Weber said his faith has helped him accept the news. He's glad to know exactly what he's facing.

"The boogeyman's out of the closet," he said. "Not knowing what you're dealing with is worse than knowing what you're dealing with. At least you know that you can size up your opponent this way."

Mayo Clinic is currently the only health provider in the United States offering choline scans to prostate cancer patients. It has added evening shifts to accommodate more patients, and plans to add more scanning equipment.

At this point, Mayo Clinic doctors will only use the scan for recurrent prostate cancer patients. They don't know yet if it would be effective in diagnosing the disease.