Author reply

Abstract

We thank Dr. Cserni for his interest and comments on our article. We would like to develop certain points he discussed. In France, where colorectal carcinoma is managed with a decentralized health care system, studies of health care practices must be population-based to be representative. In that way, our study is free of the types of selection biases that usually limit conclusions drawn from data collected in specialized centers. Contrary to Dr. Cserni's suggestion, we did not apply a preexisting mathematic model to our data. First, we established a sample of resected colorectal carcinomas representative of routine and current practices in France and then we investigated by logistic regression the relation between the regional lymph node classification of the tumor (i.e., N+ vs. N−) and the number of lymph nodes examined. Dr. Cserni wondered how 65 patients in whom no lymph nodes were recovered could be classified; in fact, they were excluded from further analysis. We agree with Dr. Cserni that not all but many lymph nodes with metastases are enlarged and thus easier to recover from the pericolic fat. In spite of the influence of many factors such as the variability of the host-tumor response, the heterogeneity of surgical and pathologic practices is likely to be the chief explanation for the variations in the number of lymph nodes examined, with the mean value for each department showing a wide range in our study, as it did for each hospital in the Large Bowel Cancer Project study.1 With regard to the “less than optimal” category (not enough lymph nodes examined), at least two survival studies (Givel et al., unpublished data and ref. 2) already have demonstrated an independent effect of the number of lymph nodes examined, with a plateau number very close to the one determined in our study. One limitation of our study was the lack of available precision regarding the location of positive lymph nodes; however, after the completion of our work we observed that the latest edition (1997) of the TNM staging system did not take into account the location of positive and examined lymph nodes. Finally, the validity of our statement that at least eight lymph nodes should be examined to assess lymph node status correctly in colorectal carcinoma patients had been reinforced by the most recent French Consensus Meeting.3 Jean Maurel M.D., Ph.D.*, * Service de Chirurgie Digestive-CHu, Caen et Registre des Tumeurs, Digestives du Calvados, CJF INSERM, Caen, France