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Accuracy of colon cancer lymph node sampling influenced by location



– Clinical guidelines recommend 12 lymph nodes or more are needed to achieve adequate sampling in colon cancer, but those guidelines may need to be revised to take into account which side the cancer is on to accurately stage a subset of patients with colon cancer, according to results of a prospective, multicenter clinical trial presented at the Society of Surgical Oncology Annual Cancer Symposium.

Ahmed Dehal, MD, of John Wayne Canter Institute in Santa Monica, Calif., presented results of the trial that compared nodal staging in right-sided vs. left-sided colon cancer in two cohorts with T3N0 colon cancer who had at least one lymph node examined: a group of 370 patients from the randomized, multicenter prospective trial; and a sampling of 153,945 patients in the National Cancer Database (NCDB). The latter was used to validate findings in the trial group.

Dr. Ahmed Dehal of John Wayne Canter Institute in Santa Monica, Calif.

Dr. Ahmed Dehal

“Tumor sidedness has been recently shown to impact survival and response to treatment, but, the relationship between tumor sidedness and nodal evaluation has not been examined,” Dr. Dehal said. “We studied a group of patients where the number of nodes needed to ensure a truly negative nodal status matters the most – in T3N0 disease, as guidelines currently recommend to administer chemotherapy in this subgroup of patients when less than 12 nodes were removed at time of surgery.” he said.

The probability of achieving true nodal negativity when 12 lymph nodes were examined was 64% for left and 68% for right colon cancer in the trial group and 72% and 77% in the NCDB cohort, Dr. Dehal said.

The analysis also examined how many nodes would need to be sampled to achieve probabilities of 85%, 90% and 95% true nodal negativity. This analysis found the numbers were consistently lower for right- vs. left-sided disease, Dr. Dehal said. For example, in the trial cohort, 27 lymph nodes would need be sampled in right-sided disease to achieve 85% probability vs. 31 in left-sided. In the NCDB cohort, those numbers were 21 and 25, respectively.

“The current threshold for adequate nodal sampling does not reliably predict the true nodal negativity in this subgroup of patients,” Dr. Dehal said. “In both cohorts – the trial and NCDB – more lymph nodes are needed to predict the true nodal negativity in patients with left compared to right colon cancer.”

These findings may help to inform revisions to existing clinical guidelines, Dr. Dehal said.

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