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Colorectal cancer research shows treatment helps

Colorectal cancer is the third most prevalent cancer and is the third largest cause of cancer-related mortality in the United States. Nationwide, it accounts for about 12 percent of all cancers and 12 percent of cancer-related mortality. About 148,300 new cases and 56,600 deaths are estimated for the year 2002 in connection with colorectal cancer.

The five-year survival for patients whose visible tumor has been completely removed by surgery is only 50 percent. The prognosis is better for those who did not have lymph node metastasis, perforation or direct extension into a neighboring organ.

Until 1990 there was no credible treatment that could be offered to those patients who were at high risk for recurrence. In 1990, Dr. Morel and colleagues from the Mayo Clinic demonstrated a 40 percent lower recurrence rate for those who were treated with a mild chemotherapy including 5FU. At the end of six years, those who received chemotherapy following surgery had a survival of 70 percent while those who had only surgery without chemotherapy had a survival of 50 percent.

Shortly thereafter, the National Institute of Health consensus conference acknowledged the benefits of chemotherapy after surgery for colorectal cancer. After that, adjuvant chemotherapy for node-positive cancers had become the standard of care in the United States. Through additional clinical trials, oncologists have shown that a six-month treatment is as good as a whole year's worth of chemotherapy that the Mayo Clinic study recommended.

Seventy-five percent of all colorectal cancers are diagnosed in patients older than 65, whereas most people in clinical trials are younger. Therefore, the validity of extrapolating the benefits observed in the younger patients to those older than 65 is questioned.

In the March 22 issue of the Annals of Internal Medicine, scientists from Columbia University in New York reported a retrospective study that strongly validated the assumption that chemotherapy benefited older patients, as well. They reached this conclusion after analyzing the records of 4,768 patients older than 65 with node-positive colorectal cancer. The editors of the Annals said, "These results remained robust in careful sensitivity analysis."

From two other studies the same group of researchers observed that only 52 percent of patients older than 65 with node-positive colorectal cancer were referred and received chemotherapy. The mortality from colorectal cancer has been falling steadily over the years because of early detection, but more noticeably among males since 1990, when chemotherapy became standard. The implication is that only half the eligible elderly patients are receiving chemotherapy and that a great potential for minimizing deaths from node-positive colorectal cancer exists for elderly patients.

An article that appeared in the Journal of Clinical Oncology evaluated the ability of patients older than 70 with good performance status to tolerate 5FU-based chemotherapy. It concluded that older patients tolerated 5FU-based chemotherapy just as well as the younger patients, further fortifying the need of offering chemotherapy to all eligible elderly patients.

_ V. Upender Rao, M.D., FACP, practices at the Cancer and Blood Disease Center in Lecanto.

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