title: “Let There Be Light” ShowToc: true date: “2023-01-11” author: “Alexandra Allen”
PDT works much the way photosynthesis does in plants, by using light to spark a chemical reaction. McCormick’s treatment began with an injection of porfimer sodium (brand name: Photofrin), a special light-sensitive drug that travels through the bloodstream and settles in cancerous cells. The drug, which the FDA has just approved for this use, is inactive until triggered by light. Two days after the injection, doctors numbed McCormick’s throat, then snaked a bronchoscope into his lung, where it emitted a red laser light. The laser caused the drug to produce an unstable form of oxygen, which made the cancerous tissue inflame and detach from the lung’s lining. The dead cancer cells ““just slough off like a scab does,’’ according to Dr. Eric Edell, vice chair of pulmonary and critical care at the Mayo Clinic in Rochester, Minn.
The use of photodynamic therapy is currently restricted in the United States, approved only for late-stage esophageal cancer and for early-stage lung cancer in patients who have no treatment alternatives (ironically, McCormick, a PDT success story, wouldn’t be eligible for the procedure today). And long-term follow-up is limited. But researchers are heartened by preliminary success rates. In a study of 102 lung-cancer patients conducted in Canada, Germany and France over the last decade, doctors eradicated early-stage tumors in 79 percent of patients after just one round of PDT. ““It kills cancer, no doubt,’’ says Edell.
The treatment is also swift–McCormick’s outpatient session lasted 15 minutes; surgery would have required a hospital visit plus six weeks of recovery. PDT can save money, too: in a 1996 Japanese study of lung-cancer treatments, researchers found that PDT cost about half as much as surgery. And it’s a whole lot less invasive. ““I didn’t feel a thing,’’ says McCormick. Doctors are now testing the procedure on everything from skin and breast cancer to macular degeneration, a progressive eye disease. ““A few years ago, we said PDT was promising,’’ says Thomas Dougherty, a research scientist at Roswell Park Cancer Institute in Buffalo, N.Y. ““Now, we say it works.''
Doctors warn that light therapy is by no means a replacement for standard treatments. Unlike chemotherapy, PDT cannot attack cancer cells that have spread throughout the body, since it works by targeting tumors. Nor is it useful on bloodborne cancers like leukemia. And because light waves cannot penetrate more than several millimeters of tissue, deeply lodged tumors are inaccessible to PDT. The therapy isn’t devoid of side effects, either: Photofrin remains in the body for about six weeks after treatment, leaving patients extremely sensitive to sunlight and bright bulbs (even a dentist’s lamp can cause an uncomfortable burn).
But that’s a side effect many cancer patients would be willing to put up with. Phillip McCormick got a bad sunburn planting his corn, but he’s been cancer-free since his treatment two years ago. To him, ““it’s the greatest thing since bubble gum.’’ His four grandkids would likely agree.
