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.
| Variable | No pCR No=184 (76.0%) | pCR No=58 (24.0% | p | Variable | No pCR No=184 (76.0%) | pCR No=58 (24.0% | p |
| Gender Female | 46 (70.8%) | 19 (29.2%) | 0.41 | Clinical T2 | 1 (16.7%) | 5 (83.3%) | 0.76 |
| Gender Female | 137 (77.8%) | 39 (22.2%) | Clinical T3 | 163 (76.5%) | 50 (23.5%) | ||
| Age (years) | 58.5(19-86) | 55.5(30-85) | 0.51 | Clinical T4 | 10 (90.9%) | 1 (9.1%) | |
| Interval ≤7weeks | 71 (83.5%) | 14 (16.5%) | 0.021 | Clinical N0 | 109 (74.7%) | 37 (25.3%) | 0.54 |
| Interval >7weeks | 63 (69.2%) | 28 (30.8%) | Clinical N1 | 61 (78.2%) | 17 (21.8%) | ||
| XRT fields 3 | 71 (76.3%) | 22 (23.7%) | 0.46 | Clinical N2 | 5 (71.4%) | 2 (28.6%) | |
| XRT fields 4 | 21 (80.8%) | 5 (19.2%) | Differentiation Poor | 30 (88.2%) | 4 (11.8%) | 0.8 | |
| CEA (ng/mL) | 5.17 +/- 6.46 | 4.04 +/- 5.52 | 0.3 | Differentiation Moderate | 123 (76.9%) | 37 (23.1%) | |
| Distance Anal Verge (cm) | 5.55 +/- 2.76 | 5.35 +/- 2.72 | 0.57 | Differentiation Well | 24 (82.8%) | 5 (17.2%) |