Response to: Comment on “Impact of tumor site on the prognosis of small bowel adenocarcinoma”

Dear Editor: We appreciate the interest in our recent report1 and the comment.2 To solve the issue of overparameterization, as suggested by Weng et al.,2 we assumed a cutoff p value of 0.10 to include potential interest parameters, thus we excluded the sex variable from the multivariate analysis (MVA). The results of the MVA are shown in Table 1. Moreover, reducing the number of variables to 2 factors (stage and tumor site) (Table 2), the results, once again, are confirmed. Stage and tumor site remain independent predictors of overall survival (OS). To test the validity of the model and answer the second question by Wang et al.,2 considering the small sample of the population, we implemented the analysis including the cross-validation with bootstrapping. To quantify the discrimination performance of the model, Harrell’s C-index was measured. The model was subjected to bootstrapping validation (1000 bootstrap resamples) to calculate the optimistic corrected estimate of C-index. The C-index for OS models was 0.70 while the corrected C-index was 0.67. Despite the small sample, the conclusions of our model seem to be robust. The potential for significant bias has already been mentioned in our report1 and the results must be considered cautiously. Large-scale studies are warranted.