all colon cancers can be cured with surgery, it is often the first course of treatment. With their test, which measures levels of known cancer-causing mutations in the blood, Choti and Diaz can tell within 24 hours after surgery if any microscopic cancer was left behind. “Basically, we count the mutations in the bloodstream,” says Choti. “The more you see, the more likely the cancer is to come back.” It is the cancer doctors can’t see that kills, so uncovering these hidden cells is key to curing the cancer. “It is these cells that get into the lungs, liver, and brain and clog normal functions in normal tissue,” says Diaz. He likens it to the viral load in HIV. “We’ve learned that if you keep the virus in check, it doesn’t kill. We can apply this same approach to cancer.” Choti says the same test can be used to tell if drug or radiation therapy is working. Typically, physicians rely on imaging, such as CT scans, to see if the tumor is getting smaller. Choti says, since the scans are not done frequently, as much as two months of therapy could go on before the doctors realize that it’s not working. “With this blood test, we could potentially know after one week, maybe after one dose, whether therapy is working,” he says. CURING BY CONTROLLING
Colon cancer is unique among cancers in that patients get what Choti calls controlled metastases. “We can cut out or destroy spots on the liver with such techniques as liver resection and ablation and cure many patients,” he says. This approach is now becoming standard care, and Choti says it’s being expanded to other GI cancers. “We have more and more data to support surgical therapy for metastases to the liver and the lung,” says Choti. It significantly improves survival.”
A new colon cancer vaccine, monoclonal antibody therapy, radio-immunotherapy, imaging-guided and robot-assisted surgery, and molecular-targeted therapies are all new approaches to treating advanced colon cancer. One of the more interesting efforts is being led by Choti and a young surgeon Timothy Pawlik. It is directed at cancers of the liver—ones that originate there and ones that begin in the colon or other organs and spread to the liver. The liver is a vital organ that humans cannot live without. Liver transplantation is an option for some patients with primary liver cancer, but not for patients with colon cancer that has spread to the liver. These patients are often told there is no surgical therapy for them. Not at Johns Hopkins, however, where Choti and Pawlik are doing what others said could not be done. As a result, they are attracting patients from around the country. One good thing about the liver is that it can regenerate itself. If there are a limited number of tumors in the liver, surgeons can take them out, and the organ rather quickly repairs itself. “We are helping patients who have tumors that require removing 70 to 80 percent of the liver, a surgery the liver could not recover from without some help,” says Pawlik Using CTs of the liver tumors and working with radiologists Pawlik determines how much of the liver will have to be removed to get all of the cancer. If it is too much, he turns to interventional radiologists for a technique called portal vein embolization that actually grows the liver. The liver has two halves, and each has a portal vein that carries blood and the critical growth factors that give the liver its unique rejuvenation abilities. The interventional radiologist uses embolization to clot and cut off the blood supply to the tumor-filled side of the liver, redirecting the blood supply to the normal side, causing it to grow. It must grow to where it repre-
“A new colon cancer vaccine, monoclonal antibody therapy, radio-immunotherapy, imaging-guided and robot-assisted surgery, and molecular-targeted therapies are all new approaches to treating advanced colon cancer. ” — M I C H A E L C H OT I
Fall 2008 —Winter 2009 I PROMISE AND PROGRESS
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