Researchers from the University of Oxford announced on Thursday that they have developed the first genetic test for predicting the likelihood that a patient's colon cancer will recur.
The test, which scans for mutations in 12 genes expressed by colon tumors, can tell patients in the early stages of colon cancer the chances that their disease will come back after treatment. That information can help doctors decide whether patients will need chemotherapy once their tumors are removed through surgery. According to the researchers who conducted the first study of the test, patients with low risk scores may expect an 8% chance of seeing their cancer come back within three years; higher-scoring patients have a 25% chance of recurrence over the same time period. Colon cancer is currently the third leading cause of cancer death in the U.S. (See pictures of cancer survivors and read their stories.)
"This is a new molecular tool that will allow clinicians to select those patients who do not require chemotherapy at all," says Dr. David Kerr, a University of Oxford professor of cancer medicine, who led the study and will present its results at the annual meeting of the American Society of Clinical Oncologists (ASCO) in Orlando at the end of May. "It will empower some patients to be cured with surgery alone."
Kerr looked at the usefulness of the test in more than 1,000 Stage 2 colon-cancer patients. At this stage, the cancer has penetrated the colon wall but has not spread beyond the colon into the lymph nodes or nearby tissues. About 90% of Stage 2 patients survive five years beyond the diagnosis. In almost all cases, surgeons remove the cancer first; studies have shown that surgery alone can cure four out of five cases of Stage 2 colon cancer. But how do patients know if they are the outlying fifth case or if they are among the fortunate who will be cured by surgery? Even doctors can't always be sure whether they have removed all the cancer or some cells have escaped into neighboring tissues such as the bladder or ovaries. So, many physicians recommend chemotherapy as a safety measure, to ensure that any remaining cancer cells are destroyed.
With the new screening test, however, doctors can now potentially spare some patients chemotherapy and exposure to its often toxic side effects. Genomic Health, a biotechnology company, is hoping to launch the test commercially in 2010. The company isn't new to the field of cancer predictors: in 2007 it released the first test of this kind to predict the recurrence of breast cancer. That screen, known as Oncotype Dx, is used widely today and relies on a 21-gene assay to tell patients how likely their cancer is to recur and whether their tumors will respond to chemotherapy.
The latter capability is something the colon-cancer screen doesn't have yet. But it's something that Dr. Leonard Saltz, a colon-cancer expert at Memorial Sloan Kettering Cancer Center, believes is necessary to make the test truly useful for doctors and patients. "What this test clearly does is tell people that you have a greater likelihood of being in the group that is at high risk or low risk of having a recurrence, but it doesn't tell you that your risk will change if you get chemo."
Still, if the screen can stratify patients by the likelihood of their cancer coming back, they might be more comfortable deciding whether to begin chemotherapy. "This is another piece of information that can guide the discussion physicians have with patients about their treatment options," says Dr. Richard Schilsky, president of ASCO and a cancer physician at the University of Chicago. And any such landmarks in that conversation are certainly welcome.