MULTIFACTORIAL ANALYSIS OF LOCAL RECURRENCES IN RECTAL-CANCER, INCLUDING DNA-PLOIDY STUDIES - A PREDICTIVE MODEL

DNA ploidy studies were performed in 188 patients operated on for rect al cancer. In order to define different risk groups of patients, a ste pwise logistic regression was carried out in 138 patients who underwen t abdominal ''curative'' resections. Thirty-seven variables were analy zed. Although several variables were significant, only three improved the prognostic value: (1) more than three positive lymph nodes (p = 0. 0007); (2) macroscopic local tumor invasion (p = 0.01); and (3) DNA pl oidy (p = 0.03). Standardized discriminant coefficients were used to o btain a model and format for predicting local recurrences. This is the first time that a predictive model for rectal cancer, using DNA ploid y as a variable, is reported. Based on calculated discriminant values (DV), patients can be divided into three subgroups: (1) low risk for l ocal recurrences (DV < -1.9, n = 56) - local recurrences were observed in two patients (3.6%); (2) moderate risk (DV between -1.9 and -0.6, n = 55) - local recurrences occurred in nine patients (16.4%); and hig h risk (DV > -0.6, n = 27) - local recurrences occurred in 14 patients (51.8%). This predictive model for local recurrences has much better prognostic value than Dukes' staging (p < 0.0001).