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Impact of a 12 Lymph Node Harvest Quality Metric on Colon Cancer Outcomes
*Ramzi Amri, *Lawrence S. Blaszkowsky, *Anne M Dinaux, *Hiroko Kunitake, Liliana G Bordeianou, David L Berger
Harvard Medical School/Massachusetts General Hospital, Boston, MA

Objective: A lymph node (LN) harvest of 12 or more nodes has become a quality metric for adequacy of resection. A <12LN yield is considered a high-risk threshold for stage II patients. In theory, as institutions achieve ≥12LN resections, there should be a migration of patients previously felt to be stage II into stage III, as a greater LN harvest should capture otherwise missed positive nodes. This should then lead to outcome improvements for stage II cases, as it will include only “true” stage II patients.
Design: Retrospective review of prospectively maintained data repository.
Setting: Tertiary care center.
Patients: All operative AJCC stage I-III colon cancer patients (2004-2011;n=926).
Main outcome measures: Changes in ≥12LN rates, recurrence and mortality over two time intervals (2004-2007;2008-2011).
Results: Staging distributions did not change significantly, while the number of stage II patients with <12LN decreased drastically from 18.1% to 2.4% (P<0.001). Concurrently, recurrence rates remained stable (P=0.289), while survival improved (P=0.025).
2004-2007
(n=461)
2008-2011
(n=465)
P-value
Stage I27.7% (137)26.9% (129)0.82
Stage III35.4% (175)35.7% (171)0.93
Stage II30.2% (149)34.2% (164)0.17
Adjuvant chemotherapy18.1%18.3%0.97
Screening diagnoses19.5%22.6%0.5
≥12LN yield81.9%97.6%<0.001
LN yield (median, IQR)17 (13-22)23 (18-30)<0.001
3-yr recurrence*10.6% ±2.716.5% ±3.00.289
5-yr recurrence*14.2% ±3.18.1% ±3.2
3-yr survival*82.9% ±3.286.8% ±2.80.025
5-yr survival*71.7% ±3.981.4% ±3.3
* Kaplan-Meier estimates (percentage outcome ±standard error)

Conclusions: In a center that already had a relatively high success rate in harvesting ≥12LN, improving the rate to nearly 100% did not impact surgical outcomes. With nearly all patients above the ≥12LN threshold, it becomes less useful as a prognostic litmus test; implying that a node of harvest of ≥12LN reached its upper limit as a quality metric. In similar situations, other factors and quality metrics should be explored to estimate risk and resection quality in stage II colon cancer patients.


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