American Surgical Association
2009 Annual Meeting Abstracts

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Predictive Factors for Pathological Complete Response for Rectal Cancer Following Neoadjuvant Therapy
*Luiz FC Lobato, *Luca Stocchi, *Daniel Geisler, *David Dietz, Victor W Fazio, *Ian C Lavery, Mathew F Kalady
Cleveland Clinic, Cleveland, OH

OBJECTIVE(S): 10-40% of advanced rectal cancer patients undergoing neoadjuvant chemoradiation achieve a pathologic complete response (pCR), which is associated with improved recurrence-free survival. This study evaluates predictors of pCR.
METHODS:Between 1997 and 2007, 342 consecutive patients with stage II and III rectal cancer who underwent neoadjuvant chemoradiation were identified from a single-institution IRB-approved colorectal cancer database. 100 patients were excluded due to concurrent IBD, FAP, HNPCC, other malignancy, urgent surgery, incomplete chemoradiation or insufficient data. Treatment was 5-FU based and the median radiotherapy dose was 5040 (4000-6100) cGy. For analysis, the cohort was stratified in 2 groups according to pathologic response (pCR/no-pCR). Pretreatment variables (see table 1) were analyzed by univariate and multivariate analysis with pCR as the dependent variable. Fischer’s exact test, Chi square, Wilcoxon rank-sum and logistic regression were used for analysis. p<0.05 was considered statistically significant.
RESULTS: A summary of the results is shown in the table. Patient demographics were statistically the same. 58 (24%) patients obtained pCR. An interval from completion of treatment to surgical resection greater than 7 weeks was significantly associated with a higher rate of pCR.
CONCLUSIONS: Despite traditional beliefs that certain patient and tumor factors influence pCR, an extended interval between completion of neoadjuvant therapy and surgery was the single most important determinant in achieving a complete pathological response.
Table1
VariableNo pCR No=184 (76.0%)pCR No=58 (24.0%pVariableNo pCR No=184 (76.0%)pCR No=58 (24.0%p
Gender Female46 (70.8%)19 (29.2%)0.41Clinical T21 (16.7%)5 (83.3%)0.76
Gender Female137 (77.8%)39 (22.2%)Clinical T3163 (76.5%)50 (23.5%)
Age (years)58.5(19-86)55.5(30-85)0.51Clinical T410 (90.9%)1 (9.1%)
Interval ≤7weeks71 (83.5%)14 (16.5%)0.021Clinical N0109 (74.7%)37 (25.3%)0.54
Interval >7weeks63 (69.2%)28 (30.8%)Clinical N161 (78.2%)17 (21.8%)
XRT fields 371 (76.3%)22 (23.7%)0.46Clinical N25 (71.4%)2 (28.6%)
XRT fields 421 (80.8%)5 (19.2%)Differentiation
Poor
30 (88.2%)4 (11.8%)0.8
CEA (ng/mL)5.17 +/- 6.464.04 +/- 5.520.3Differentiation
Moderate
123 (76.9%)37 (23.1%)
Distance Anal Verge (cm)5.55 +/- 2.765.35 +/- 2.720.57Differentiation
Well
24 (82.8%)5 (17.2%)


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