Objective To retrospectively analyze the risk factors for secondary catheter ectopia during PICC retention in cancer patients, so as to provide clinical references for effective prevention, prediction, and timely treatment of secondary ectopia in the future. MethodsA retrospective analysis was conducted on the risk nomogram model obtained from 19 208 cancer patients who underwent PICC catheterization, catheter maintenance, and extubation at our vascular access nursing center of a tertiary general hospital specializing in oncology in Shanghai from March 2018 to May 2023. The model was then externally validated using 4 951 patients from June 2023 to July 2024. The chi square test was used for univariate analysis, and the binary unconditional logistic regression method was used for multivariate analysis. Establish a modeling group and an internal validation group in a 7:3 ratio, develop predictive models for relevant nomogram, and conduct external validation for application. Calibration curves and Hosmer lemeshow (H-L) goodness of fit tests were used to evaluate the predictive performance of the model. ResultsThe incidence of secondary ectopia during PICC retention in cancer patients was 1.37% (264/19 208 patients). Univariate analysis showed that gender, primary ectopia, catheter placement time, body mass index, catheter dislodgement, and catheter blockage had an impact on secondary ectopia (P<0.05). Multivariate analysis showed that gender, primary ectopia, body mass index, catheter dislodgement, and catheter blockage were independent risk factors for secondary ectopia (P<0.05). Based on the above five factors, the nomogram was constructed, and the AUC of the model on the training set, testing set, and external validation set were 0.811, 0.757, and 0.724, respectively. The H-L goodness of fit test results showed that the predictive model had a good fit on the testing set and external validation set, with P-values of 0.12 and 0.13, all greater than 0.05. The calibration curve showed that the model exhibited good predictive accuracy. ConclusionMale patients with a history of primary ectopic occurrence, a body mass index (BMI) ≥28 kg/m2, catheter dislodgement, or catheter blockage are at an increased risk of secondary ectopic occurrence during PICC catheterization. The nomogram model established in this study, validated internally and externally, has good predictive ability and discrimination, which is beneficial for clinical screening of patients with different degrees of risk, in order to timely take targeted prevention and effective treatment measures, ultimately reducing the occurrence of secondary ectopia and the associated risks later.