Currently, there are no reliable prediction models for predicting major complications in patients with esophageal cancer. Although several studies have developed nomograms to predict poor prognosis in patients with esophageal cancer, most are limited to predicting postoperative mortality [14–16]. Thus, we retrospectively analyzed the clinical data of 372 patients to determine the predictors of major complications in patients with esophageal cancer in the early postoperative period. The results showed that age, preoperative radiotherapy, length of surgery, and PNI were independent predictors associated with major complications within 30 days after radical esophageal cancer surgery. We analyzed these associated independent predictors and developed and validated a Nomogram.
The specific anatomical site of the esophagus and the difficulty in defining the cancerous part of the esophagus lead to a complex and long-lasting esophagectomy procedure. Besides, those who develop the disease are older and prone to numerous comorbidities, and the incidence of postoperative complications varies widely. In our cohort, complications were evaluated according to the Calvien-Dindo complication grading system, with grade III and above complications considered major complications. The incidence of major complications in our study reached 20.2%, which is consistent with 21.2% in the study of S.J. Davies et al. [17].
Furthermore, advanced age was associated with an increase in postoperative complications. In our study, the incidence of major postoperative complications was significantly increased in patients aged ≥ 60 years. This result was similar to the findings of Qi et al. [18]. Our Multivariable analysis showed that prolonged operative time was an independent risk factor for serious postoperative complications. Operative time > 3 hours was not an independent risk factor associated with postoperative complications in the study of Qi [18] et al., whereas operative time was included in our study as a continuous variable in the analysis. There may also be some heterogeneity due to differences in the study area and the level of medical technology development. Our results showed that preoperative radiotherapy was an independent risk factor for serious postoperative complications in patients with esophageal cancer. Patients in our cohort who underwent preoperative radiotherapy involved the early refusal of surgery, advanced age, cardiopulmonary comorbidities, and other reasons requiring radiotherapy followed by selective surgery; in addition, patients often experienced lymphopenia after preoperative radiotherapy, resulting in decreased immune function. Therefore, considering multiple factors, patients in this cohort who underwent preoperative radiotherapy had a higher incidence of postoperative complications and a significantly higher probability of major complications.
The ASA scoring system allows for the rapid classification of patients based on their physical status and comorbidities and can be used for preoperative assessment of morbidity and mortality in surgical patients. Wen-Quan Yu, Gooszen et al. reported that ASA grade ≥ III is an independent risk factor for major complications such as anastomotic fistula [5, 19]. Although ASA grade ≥ III was not statistically significant in multifactorial analysis, this may be due to the heterogeneity of our study. Therefore, we combined our experience in clinical work and included ASA grading in the Nomogram.
Our study demonstrates that low PNI is associated with an increased incidence of major postoperative complications. The mechanism of the correlation between PNI and postoperative complications in patients with esophageal cancer is unclear and may be determined by the role of albumin and lymphocytes. Albumin is the most abundant protein in human serum, and its concentration not only reflects the nutritional status of the body and participates in maintaining the body's immune function but also can stabilize cell growth and DNA replication and plays an essential role in antioxidant, anti-inflammatory, and apoptosis prevention [20]. Studies have confirmed that low preoperative protein levels are associated with poor prognosis in patients with gastrointestinal malignancies [21]. And lymphocytes reflect the cell-mediated immune response. Tumor-infiltrating lymphocytes in the tumor microenvironment play an important role in anti-tumor immunity. A decrease in lymphocytes reduces the anti-tumor response of lymphocytes, creating an environment of low lymphocyte infiltration suitable for tumor cell infiltration and metastasis, predicting a more infiltrative tumor [22]. Therefore, the low PNI status of patients may provide a favorable microenvironment for this immunosuppressed state.
PNI is a simple, non-invasive, and easily accessible index. Accordingly, we developed a new nomogram based on PNI to predict major complications in patients with esophageal cancer in the early postoperative period. Based on multivariate analysis and the results of previous studies, we developed the new nomogram by including five variables, including age, preoperative radiotherapy, ASA classification, duration of surgery, and PNI. We evaluated the performance of the nomogram using ROC curves and calibration curves. The area under the ROC curve (AUC) for major complications was 0.699, demonstrating good accuracy. The calibration curve for the probability of major postoperative complications showed good agreement between the nomogram's predicted and actual observed values. The DCA curve was applied to assess the net benefit of the nomogram for patients. The DCA curve showed that the nomogram resulted in a positive net benefit for patients within a threshold probability range of 0.05–0.60. In addition, the NRI showed that the predictive accuracy of this nomogram was better than that of TNM staging (NRI > 0). IDI showed an improvement in the accuracy of the nomogram in predicting major complications compared with TNM staging. In conclusion, the above validation methods showed that the newly constructed column line graph model had the better net benefit and predictive accuracy. This column line graph is the first time to predict major postoperative complications in patients with esophageal cancer by PNI. In clinical practice, it may help to identify patients at high risk of major postoperative complications at an early stage, which is beneficial for clinicians to target individualized treatment plans, establish perioperative early warning mechanisms, intervene, diagnose and treat early, prevent and reduce the incidence of major postoperative complications in patients, and thus provide patients with better clinical services and medical benefits.
The following limitations exist in this study: 1. This is a retrospective study, and selection bias may exist, so we trained our investigators and included the study population strictly according to the nadir criteria to minimize selection bias. 2. There is no uniform standard for the optimal PNI cut-off value; in this study, the ROC curve determined the optimal PNI cut-off value. However, our PNI cut-off value was similar to Qi [18] et al. (48.6 vs. 48.33). 3. The follow-up period in this study was only 30 days postoperatively, and there was a lack of long-term follow-up information, and we would conduct further long-term follow-up in the future, which may lead to different results. 4. The clinical data in this cohort were obtained from a single medical institution, and we intend to conduct further prospective studies with large samples for external validation to confirm our results.
In conclusion, PNI is an essential predictor of postoperative complications. Although PNI is associated with postoperative complications, previous studies have not included PNI in nomograms to develop predictive models. We created a simple and practical column line chart based on PNI, which has good predictive power for major postoperative complications in patients with esophageal cancer. In clinical practice, patients can be risk-stratified according to our Nomogram to provide early nutritional support and enhance perioperative management and monitoring in high-risk patients for maximum benefit.