June 2, 2003 (Chicago) - Two drugs, one experimental and one already on the market, may change the way doctors treat colon cancer in the future.
After years of dashed hopes and false starts, cancer researchers here at the American Society of Clinical Oncology's 39th annual meeting finally report positive results for an experimental genetically-engineered drug designed to starve tumors by denying access to the body's blood supply.
The drug, called Avastin, increased survival in patients with colorectal cancer that had already spread to other organ systems -- adding a little more than four months to survival. While that increase might seem small, researcher Herbert I. Hurwitz, MD of Duke University Medical Center in Durham, N.C. tells Web MD that "it represents a 30% increase in survival and is significant." He notes that just 10 years ago there were no available colon cancer treatments for advanced disease.
Moreover, Hurwitz says the finding shows that targeting the tumor's blood supply may be a useful colon cancer treatment, but he stopped short of saying that the new finding finally validates anti-angiogenesis, which is the term used to describe treatments aimed at blocking vascular endothelial growth factor or VEGF. This growth factor allows tumors to grow tiny blood vessels that tap into the body's blood supply and nourish the tumor. Theoretically a drug that blocks this growth factor should shrink tumors, but previous studies failed to prove this concept.
In the new study Avastin was added to traditional chemotherapy in about 400 patients with previously untreated advanced colon cancer. In another 400 patients, the colon cancer treatment consisted of standard chemotherapy without Avastin, says Hurwitz.
Hurwitz noted that this is not a cure for colon cancer, but treatment with Avastin increased the average time to disease progression from about six months to more than 10 months, and increased survival from 15 to 20 months.
The colon cancer treatment is not without risk, says Hurwitz. He says that six patients in the Avastin arm had serious side effects and one patient died, while there were no serious side effects in the patients receiving the standard colon cancer treatment.
Robert Mayer, MD, director of the Center for Gastrointestinal Oncology at the Dana-Farber Cancer Institute in Boston tells WebMD that the results should be viewed with caution. He says "in other studies -- for example studies in breast cancer -- this was not effective."
Avastin, which is made by Genentech, has not yet received FDA approval and therefore is not available outside of clinical studies.
But two other studies presented at this meeting suggest that a chemotherapy drug approved last year, Eloxatin, helps slow progression and relieve symptoms when added to standard colon cancer treatment for advanced cancer, says Mace L. Rothenberg, MD, professor of medicine at the Vanderbilt-Ingram Cancer Center in Nashville, Tenn.
Rothenberg says that about 10% of patients treated with Eloxatin plus standard chemotherapy responded to treatment while less than 1% of patients receiving standard treatment responded.
Even more encouraging, a second study found that when colon cancer patients are treated similar to breast cancer patients -- surgery followed by chemotherapy -- use of Eloxatin resulted in a 23% reduction in cancer relapse.
Aimery de Gramont, MD, a medical oncologist at Hopital Saint Antoine in Paris, France, says the finding will change the standard of care for many patients with colon cancer. He says that following this colon cancer treatment plan could save 3,000 lives in the U.S. and as many as 5,000 lives in Europe.
Mayer says the results are impressive and he predicts that they will hold up under scrutiny. "This looks substantial and I think it is," he says.
About 900,000 cases of colon cancer are diagnosed around the world each year. About 80% of these patients undergo surgery and have no evidence of cancer after surgery, yet about 30% to 40% of these surgically "cured" patients will relapse, he says. "So this treatment is likely to save lives."
Source: American Society of Clinical Oncology 39th Annual Meeting late breaking abstract: "Anti-angiogenesis drug extends survival in patients with metastatic colorectal cancer"; Abstract 1011: "Final results of a phase III trial of 5-FU/leucovorin versus oxaliplatin versus the combination in patients with metastatic colorectal cancer following irinotecan, 5-FU and leucovorin"; Abstract 1015: "Oxaliplatin/5-FU/LV in adjuvant colon cancer: results of the international randomized MOSAIC trial."