Under the Microscope: Cancer Biomarkers

Mark Roll’s pulmonary doctor was so astonished to learn that his stubborn cough was due to lung cancer that he tracked Roll down on a warm June evening in 2012 to tell him right away. The call came on Roll’s mobile phone as he napped in the car, awaiting his wife and daughter, who were shopping. Roll had never smoked, and the doctor suspected his cough might have come from exposure to a fungus on a trip from the previous year. Roll wondered about that trip, as well: How could he have hiked 63 miles over 12 days in Cimarron, N.M., at an elevation of 12,000 feet with 50 pounds of gear and supplies in his backpack, yet apparently be so sick now.

Not only did the diagnosis confirm Roll had lung cancer but scans found tumors in both of his lungs, his bones and in his brain. A special test of the tumor revealed something else: it contained a mutation in the EGFR gene, which happens more often than not in nonsmokers who develop lung cancer. Often, the results of these special tests can help in all stages of cancer treatment. In Roll’s case, his tumor’s EGFR mutation was a perfect target for Tarceva (erlotinib).

Roll started on Tarceva as soon as his mutation was identified, and the treatment allowed him to put cancer in the rearview mirror for the time being. His brain tumors are dwindling, his right lung is clear, and the tumors in his left lung are stable. His stamina returning, the 53-year-old was able to dance for hours at his oldest daughter’s wedding. “Until that day they put me on oxygen I’m not going to worry about it,” Roll says.

Biomarkers are changing the way doctors diagnose, treat and monitor cancer. Tests for biomarkers can find misbehaving genes or other telltale signs that can help with treatment decisions. These tests might be as simple as using a chemical detection method that stains certain proteins in cancer cells or as elaborate as genetic sequencing to determine a specific mutation unique to cancer cells but not found in healthy cells.

Traditional chemotherapy has been more of a one-size-fits-all approach, with some patients responsive and others not. Now, instead of giving people a simple diagnosis of lung cancer or breast cancer, doctors often are able to provide much more detailed information. “Diagnosing and treating cancer this way is a whole new ballgame, and that’s the beauty of it,” says Mark Kris, chief of thoracic oncology at Memorial Sloan-Kettering Cancer Center in New York.

In some types of cancer, treatments have been developed to target a mutation. For example, in non-small cell lung cancer, a mutation in the ALK gene makes an abnormal protein, which fuels the cancer. The drug Xalkori (crizotinib) is designed to block that protein. But if the cancer carries a mutation that is different from the drug’s intended target, there’s no reason to treat the patient with at drug that won’t work. In some cases, the presence of a mutation in a tumor may mean there are no effective targeted treatment options.

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