Lymph nodes in colon cancer – national data. Tarik Sammour Ryash Vather Arman Kahokehr Andrew B. Connolly Andrew G. Hill

Introduction Majority of colon cancer patients are potentially curable at diagnosis Surgery is offered on this basis Single most important prognostic factor is lymph node status. 2

Dukes B How many nodes are required for accurate differentiation of Dukes B cancers? Controversial “Ideal” number of nodes varies: 6 – 17. 12 nodes generally accepted as optimum by consensus.

Recent Middlemore study 216 patients with Dukes B colon cancer Jan 1993 - Dec 2001 5 year follow-up

<16 nodes gives recurrence rates similar to that expected in Dukes B cases (25-30%). Drop from 13-16 to 17-20 is significant (p=0.0368) Drop <16 to >16 is significant (p=0.0001) p=0.0001

Conclusion Dukes B patients with > 16 nodes in the sample had a significant reduction in recurrence.

Need to verify this finding in a larger subset of patients.

Methods NZ Cancer Registry data All patients who underwent resection for colon cancer Jan 1995 – July 2003. Looked at Dukes B and C patients Exclusions: Dukes A Distant mets preop No TNM / Dukes stage recorded

Results 4,309 patients included in analysis Mean age 70 years (16 – 100) Euro 93.4% Maori 2.8% PI 0.8% Other 2.9% R sided (including transverse) 57.3% L sided 43.7%

Who had more nodes? Factors associated with higher node retrieval Younger age p < 0.0001 Females 14.4 vs 13.4 Males, p 0.001 R sided cancer 15.2 vs 12.4 L sided, p < 0.0001 Pacific islander 17.8 vs 14.0 for rest, p 0.016

VS More nodes Fewer nodes

Dukes B

Dukes B 5 year mortality 31% Mean number of nodes 13.7 (range 1 – 99) Death Survival Mean number of nodes examined 11.9 14.5 P < 0.0001

Dukes B Seemingly linear increase in survival with more lymph nodes in the specimen. What if you factor in confounders such as age, sex, site, and ethnicity? => COX regression analysis

No reduction in survival past 16 nodes

Dukes C

Dukes C 5 year mortality 60.4% Mean number of nodes 13.8 (range 1 – 99) Death Survival Mean number of nodes examined 13.1 14.8 P < 0.0001

No reduction in survival past 16 nodes

Conclusions Number of sampled lymph nodes predicts mortality in Dukes B and C colon cancer. Survival increases up to 16 lymph nodes, after which survival benefit is negligible. This finding is consistent with our local data. Should inform patient counselling and decision making regarding chemotherapy referral.