Abstracts
1999 Digestive Disease Week

# 2082 PRIMARY TUMOR RESPONSE TO PREOPERATIVE CHEMORADIATION DOES NOT INSURE THE ABSENCE OF REGIONAL LYMPH NODE METASTASES IN PATIENTS WITH LOCALLY ADVANCED RECTAL CANCER.
J Fleming, K Hunt, B Feig, Stephen Curley, L Ellis, N Janjan, K Cleary, J Skibber, MD Anderson Cancer Ctr, Houston, TX

Preoperative chemoradiation for locally advanced rectal cancer allows for curative resection with sphincter preservation. The pathologic response of the primary to chemoradiation is well documented; however, the extent of residual nodal disease is unknown. It is our hypothesis that nodal metastases are present in a significant number of patients with a complete or partial pathologic response of the primary tumor to preoperative therapy.
Methods: Prospective clinicopathologic and treatment data was collected for consecutive patients presenting with primary ultasound-staged (uT) T3 or T4 rectal adenocarcinoma. All patients were treated preoperatively with continuous infusion 5-FU and external beam irradiation followed by extirpative surgery including total mesorectal excision. Detailed pathologic evaluation of the specimen including identification and extent of bowel wall penetration of viable neoplastic cells and the presence or absence of residual nodal involvement within the mesorectum was performed. Statistical significance of the data acquired was assessed by chi-squared analysis.
Results: A total of 105 patients presented with primary uT3(n=90) or uT4 (n=15) rectal adenocarcinoma. Comparing pre- and post-treatment T stage, 63(60%) of patients experienced a complete or partial response to therapy. Post-operative pathologic evaluation of the primary tumor after chemoradiation identified no viable neoplastic cells in 25 (24%) of the patients. Distribution of T stage included: T4 in 14(13%), T3 in 32(30%), T2 in 30(28%) and T1 in 4(3%) of patients. A median of 5 nodes (range:0-27) were found in the mesorectum after excision, and 22(21%) of the patients had viable tumor present within perirectal nodes. Failure to achieve a complete or partial response at the primary site was associated with residual nodal metastases (p=0.0024). The distribution of nodal metastases with respect to pathologic (post-chemoradiation) T stage is shown in the figure. Of patients with a complete pathologic response of the primary, 2 of 25 (8%) had pathologic lymph nodes remaining within the mesorectum, and 6 of 34(18%) patients with less than full thickness involvement of the bowel wall had identifiable lymph node metastases.
Conclusion: Failure of the primary tumor to respond to preoperative therapy predicts the presence of residual lymph node metastases: however, the degree of response at the primary site does not accurately predict the absence of nodal metastases after preoperative chemoradiation of T3 and T4 rectal cancer.

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