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By Will Boggs, MD

NEW YORK (Reuters Health) Jan 27 - Among patients with colorectal cancer, survival rates are associated with the lymph node ratio (LNR) -- i.e., the number of tumor-infiltrated nodes divided by the total number of resected nodes -- German researchers report in the December 2008 Annals of Surgery.

"LNR is a more accurate prognostic parameter than just the presence of lymph node metastases," Dr. Robert Rosenberg told Reuters Health.

Dr. Rosenberg and colleagues at the Technische Universitaet Muenchen compared LNR to other prognostic factors using a database of patients with colorectal cancer who underwent resection between 1982 and 2006.

About one-fifth of the patients had 1 to 3 tumor-positive lymph nodes, the authors report, and a similar proportion had more than 3 tumor-positive nodes. The median number of resected lymph nodes was 16, including 19.5 for patients with colon cancer and 15 for patients with rectal cancer.

LNR thresholds of 0.17, 0.41, and 0.69 provided the highest discrimination of 5-year survival.

Specifically, 5-year survival was 87.1% for patients with no lymph node metastases, 60.6% for those with a LNR between 0 and 0.17, 34.4% for those who had a LNR between 0.17 and 0.41, 17.6% for those with a LNR between 0.41 and 0.69, and 5.3% for those with a LNR above 0.69.

LNR remained an independent prognostic factor after accounting for lymph node status, tumor grade, the presence of metastases, patient age, and other independent factors, the researchers note.

"Take a look at the LNR and you have first a real quality indicator of the surgeon and/or the pathologist, which means if you send patients to a hospital which always resects fewer than 12 lymph nodes, the quality is not adequate," Dr. Rosenberg commented.

"I believe that the LNR can affect the postoperative treatment," he added. "If you have a high LNR, your prognosis is bad and you may need more aggressive chemotherapy than somebody who has a low LNR. But this has to be shown in future studies."

Ann Surg 2008;248:968-978.