Sticking it to Cancer
A new vaccine, amazingly, may rid the world of cervical cancer, while doctors aim other needles at more killer tumors
The problem in this case--in all cancer cases--is that tumors were evading his immune system, because that system didn't recognize them as foreign invaders. So Petersik turned to a Seattle-based company called Dendreon that teaches old cells new tricks with a therapeutic vaccine called Provenge.
Doctors take cells designed to spot intruders out of the patient's body, juice them with prostate cancer molecules, and put them back in the patient. These cells then point the immune system toward the real enemy. In January, as part of a clinical trial, Petersik lay still for three hours while the vaccine flowed into his body through an IV drip. "I got infused three times," says Petersik. "There had been a large tumor in my lower back. It practically disappeared. And the pain it caused went away, too."
Dendreon recently completed studies of 225 patients like Petersik and found that Provenge increased their survival by nearly 4
Loaded up. Pancreatic cancer is another new target for vaccines. About 33,000 people will be diagnosed with it this year, and almost all of them will soon die. The PanvacVF vaccine, made by a company called Therion in Cambridge, Mass., is a shot in the arm with a benign virus that has been loaded with genes culled from pancreatic cancer cells. The shot gets the immune system to produce cancer-killing cells, and booster shots every few weeks or months keep the reaction going. "We're trying to get the patient's immune system to view the tumor as a bad organ, like an organ transplant, and reject it," explains Therion's Thomas Schuetz, a medical oncologist. So far, in small studies, he's seen vaccinated patients generate a lot more of these tumor-killing cells. Another vaccine, Gvax, is an injection of pancreatic cancer cells along with a molecule designed to attract immune cells and sensitize them to the deadly growth.
But these studies have attracted critics along with hopeful patients. "A lot of these vaccine trials are small, and their response rates are low," says Mario Sznol, a medical oncologist at Yale. "That means some positive findings could simply be due to chance." Steven Rosenberg, chief of the surgery branch at the National Cancer Institute, is more blunt. "There's been a lot of hype here. Most of these trials don't show tumor shrinkage, which is the gold standard of success."
Rosenberg has his own solution, focused on making tumors not just shrink but melt away. He's targeting advanced metastatic melanoma, a disease in which only 16 percent of patients live for five years after diagnosis. A few immune cells, called TIL cells, do attack such tumors, but there aren't a lot of them. So Rosenberg picks them out and grows the most aggressive ones in the lab, multiplying them by the billions. Then he kills off old, ineffective immune cells still in the patient with heavy doses of toxic chemo and replaces them with the new cancer slayers. "They bring your cells back to you, in these bulky plastic bags, and hook up an IV tube," says melanoma patient Jessica Mosher, 31, of Manassas, Va., who first was treated in 2002. What had started as a small spot on her back a year earlier had morphed into tumors in her lungs, her liver, and a huge one in her back. "I knew there were billions of cancer-fighting cells in the bags, and I got more and more excited."
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