Quote:Cyrus Farivar 04.02.07

Imagine you could treat cancer by taking a pill, then directing a laser light toward the location of the tumor. The growth would dissolve with no chemotherapy, and no harm to healthy tissue.

It might sound futuristic, but a select number of cancer patients already benefit from the method, called photodynamic therapy. An upgrade for the procedure could save thousands more cancer patients from the horrors of chemotherapy.

"It's an approach that I really like," said Karen Brewer, a professor of chemistry at Virginia Tech and lead author of the research on Tuesday at the American Chemical Society annual conference in Chicago. "We stand to make a really major improvement, instead of trying to treat one new kind of tumor or make the patient a little less sick."

Although chemotherapy has improved over the past decade, the treatment still damages healthy tissue and causes other unpleasant side effects like nausea and a weakened immune system. The researchers hope their work will spare patients from chemo's ravages and even the surgery usually necessary to remove a tumor.

"Rather than using a scalpel, you're using light and a molecule that then reacts with the cells," said William Phelps, scientific program director at the American Cancer Society.

The new treatment, however, still needs to be tested head to head with the current version of photodynamic therapy, Phelps said.

The technique starts with a compound called a photosensitizer, a type of molecule that latches itself onto a tumor and when exposed to focused light excites oxygen, destroying the tumor cells. The treatment's reliance on oxygen, however, has been a limitation because smaller, newer tumors don't contain any.

The new technology gets around the problem by killing the tumor with "supramolecules" -- large molecular assemblies that act as anti-cancer fighting forces. The supramolecules deliver the drug directly to the tumor's DNA -- a process known as DNA cleavage.

Once the drug (the set of supramolecules) is ingested (or in the case of skin cancer, applied as a cream), a light (usually from fiber optics or a laser) focused on the site of the tumor activates the DNA cleavage.

"This has a distinct virtue of being able to get the tumor before it's generated its own blood supply," said Brian Storrie, a professor of physiology and biophysics at the University of Arkansas for Medical Sciences.

But what if a tumor is inside the body, such as on the liver or other internal organs? As anyone who has played with a red laser pointer knows, red light can permeate human tissue. So red or infrared light can reach some, but not all, tumors. "Research is certainly underway to work on better light delivery methods," Brewer said.

Brewer has performed tests using her technique on raw DNA, cell cultures and E-coli. She and her will begin tests on horses "any day now," because horse skin cancer is remarkably similar to human skin cancer.